Phospholipid-Based Reverse Micelle Structures in Vegetable Oil Modified by Water Content, Free Fatty Acid, and TemperatureClick to copy article linkArticle link copied!
- Paavo A. Penttila?*Paavo A. Penttila?*E-mail: [email protected]. Phone: +358 (0)50 476 6800.Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandLarge-Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, F-38000 Grenoble, FranceMore by Paavo A. Penttila?
- Sampsa VierrosSampsa VierrosDepartment of Chemistry and Materials Science, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandMore by Sampsa Vierros
- Katja UtriainenKatja UtriainenDepartment of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandMore by Katja Utriainen
- Nico CarlNico CarlLarge-Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, F-38000 Grenoble, FranceMore by Nico Carl
- Lauri RautkariLauri RautkariDepartment of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandMore by Lauri Rautkari
- Maria SammalkorpiMaria SammalkorpiDepartment of Bioproducts and Biosystems and Department of Chemistry and Materials Science, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandMore by Maria Sammalkorpi
- Monika O?sterbergMonika O?sterbergDepartment of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, FI-00076 Espoo, FinlandMore by Monika O?sterberg
Abstract
Colloidal assemblies of phospholipids in oil are known to be highly sensitive to changes in system composition and temperature. Despite the fundamental biological and high industrial relevance of these aggregates, the mechanisms behind the structural changes, especially in real oils, are not well understood. In this work, small-angle X-ray scattering (SAXS) was combined with molecular dynamics simulations to characterize the effects of oleic acid, water, and temperature on self-assembled structures formed by lecithin in rapeseed oil. SAXS showed that adding water to the mixtures caused the precipitation of liquid-crystalline phases with lamellar or hexagonal geometry. The combination of SAXS and molecular dynamics simulations revealed that stable spherical reverse micelles in oil had a core radius of about 2 nm and consisted of approximately 60 phospholipids centered around a core containing water and sugars. The presence of oleic acid improved the stability of reverse micelles against precipitation due to the increase in the water concentration in oil by allowing the reverse micelle cores to expand and accommodate more water. The shape and size of the reverse micelles changed at high temperatures, and irreversible elongation was observed, especially in the presence of oleic acid. The findings show the interdependency of the structure of the reverse micellar aggregates on system composition, in particular, oleic acid and water, as well as temperature. The revealed characteristics of the self-assembled structures have significance in understanding and tuning the properties of vegetable oil-based emulsions, food products, oil purification, and drug delivery systems.
Introduction
Experimental Section
Materials
Preparation of Micellar Solutions
sample name | water (wt %) | oleic acid (wt %) | phase separation |
---|---|---|---|
W0(0.8) | 0.019 | 0 | no |
W0(3) | 0.070 | 0 | yes |
W0(13) | 0.32 | 0 | yes |
W0(0.8) + O0(13) | 0.019 | 5 | no |
W0(3) + O0(13) | 0.070 | 5 | yes (weak) |
W0(40) + O0(13) | 1.0 | 5 | yes |
W0(100) + O0(13) | 2.5 | 5 | yes |
W0(0.8) + O0(27) | 0.020 | 10 | no |
W0(0.9) + O0(52) | 0.021 | 20 | no |
The approximate water/lecithin (W0) and oleic acid/lecithin (O0) molar ratios are indicated in the sample name, with the numbers in parentheses.
Small-Angle X-ray Scattering
Computational Methods
nDOPC | nH2O | nsugar | ntriolein | t?(ns) |
---|---|---|---|---|
11 | 11 | 0 | 835 | 200 |
23 | 23 | 0 | 833 | 200 |
46 | 46 | 0 | 822 | 200 |
25 | 25 | 5 | 804 | 200 |
46 | 46 | 9 | 821 | 200 |
67 | 67 | 13 | 814 | 500 |
Results and Discussion
Phase Behavior of the Mixtures at Room Temperature
diffraction peaks | |||
---|---|---|---|
sample | order of reflection | q (nm?1) | structure |
W0(3) | 1 | 1.227 | lamellar, d?=?5.121 ? 0.001?nm |
2 | 2.454 | ||
3 | 3.682 | ||
W0(13) | 1 (L) | 1.137 | lamellar, d?=?5.5242 ? 0.0003?nm |
2 (L) | 2.275 | ||
3 (L) | 3.412 | ||
10 (H) | 0.943 | hexagonal, d?=?7.691 ? 0.001?nm | |
11 (H) | 1.634 | ||
20 (H) | 1.887 | ||
W0(40) + O0(13) | 10 | 0.728 | hexagonal, d?=?9.95 ? 0.01?nm |
11 | 1.263 | ||
20 | 1.460 | ||
21 | 1.929 | ||
W0(100) + O0(13) | 10 | 0.672 | hexagonal, d?=?10.791 ? 0.008?nm |
11 | 1.165 | ||
20 | 1.346 | ||
21 | 1.777 |
The distance d refers to the lamellar period in a lamellar crystal and to the nearest-neighbor distance between cylinders in a hexagonal crystal.
Effects of Water and Oleic Acid on the Reverse Micelle Morphology at Room Temperature
sample | NV2(??)2 (cm?1) | R?(nm) | ? |
---|---|---|---|
W0(0.8) | 0.3156???0.0006 | 2.119???0.002 | 1.000b |
W0(3), supern. | 0.0589???0.0001 | 2.111???0.002 | 1.000b |
W0(0.8) + O0(13) | 0.2523???0.0006 | 1.915???0.003 | 1.000b |
W0(3) + O0(13), supern. | 0.2301???0.0005 | 2.235???0.003 | 1.000b |
W0(3) + O0(13), precip. | 0.409???0.002 | 2.238???0.005 | 1.000b |
W0(0.8) + O0(27) | 0.2715???0.0005 | 1.79???0.01 | 1.48???0.03 |
W0(0.9) + O0(52) | 0.3134???0.0005 | 1.88???0.01 | 1.63???0.02 |
Parameters R and ?R correspond to the equatorial and polar radii, respectively.
Value fixed in order to obtain a realistic error estimate for R.
Detailed Structure of Lecithin-Based Reverse Micelles
Effects of Heating on the Reverse Micelles
Conclusions
Acknowledgments
The SAXS experiment (experiment IN-1068) was performed at beamline ID02 of the European Synchrotron Facility (ESRF). We thank Dr. Michael Sztucki from the ESRF for providing assistance in using the beamline and Dr. Dominic Hayward from Institut Laue-Langevin (ILL) for helping with the experiments. We also thank the Emil Aaltonen Foundation (P.A.P.), the Academy of Finland (grant nos. 315768 (P.A.P.) and 309324 (M.S.)), and the Aalto University School of Chemical Engineering Doctoral Programme (S.V.) for financial support. We are grateful for the support of the FinnCERES Materials Bioeconomy Ecosystem. The computational resources of the CSC IT Centre for Science, Finland and of RAMI ? RawMatTERS Finland Infrastructure are also gratefully acknowledged.
References
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- 6Fiordemondo, D.; Stano, P. Lecithin-Based Water-In-Oil Compartments as Dividing Bioreactors. ChemBioChem 2007, 8, 1965? 1973, DOI: 10.1002/cbic.200700112Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlGhu7bK&md5=7a427b9bc0fda2131238f41141a3107aLecithin-based water-in-oil compartments as dividing bioreactorsFiordemondo, Deborah; Stano, PasqualeChemBioChem (2007), 8 (16), 1965-1973CODEN: CBCHFX; ISSN:1439-4227. (Wiley-VCH Verlag GmbH & Co. KGaA)Like liposomes, water-in-oil (w/o) emulsions have recently been used as bioreactors, since they permit facile compartmentation, and therefore the creation of a synthetic cell-like structure. We show here for the first time that lecithin-based w/o compartments can also be used for these purposes and in particular as compartments for hosting complex biochem. reactions that lead to protein synthesis. The expression of enhanced green fluorescent protein (EGFP), used as a model reaction, was followed by fluorescence microscopy. EGFP was synthesized inside the bioreactors either through simultaneous incorporation of all components for transcription and translation reactions in a single emulsion, or through the mixing of four different emulsions, each contg. only part of the mol. machinery. Mech. energy (i.e., stirring) must be provided to the system in order to force solute exchange and/or fusion processes between droplets. Finally, we demonstrate that, in the presence of excess lecithin, preformed w/o compartments can undergo spontaneous division, reducing the av. droplet size, increasing the no. of droplets, and continuing the protein expression after the division. We briefly comment on how this type of work extends and links the previously reported work on self-reprodn. in vesicles, micelles and reverse-micelles.
- 7Angelico, R.; Ceglie, A.; Olsson, U.; Palazzo, G. Phase Diagram and Phase Properties of the System Lecithin-Water-Cyclohexane. Langmuir 2000, 16, 2124? 2132, DOI: 10.1021/la9909190Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXmvVyqsA%253D%253D&md5=83a489af6f714d1965c4e2cd468086f2Phase Diagram and Phase Properties of the System Lecithin-Water-CyclohexaneAngelico, R.; Ceglie, A.; Olsson, U.; Palazzo, G.Langmuir (2000), 16 (5), 2124-2132CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The isothermal quasi-ternary phase diagram of the lecithin-cyclohexane-water system was constructed at 25 °C using a combination of polarizing microscopy, small-angle X-ray diffraction, and NMR techniques. The system contains four lyotropic liq.-cryst. phases and two isotropic liq. phases. Apart from the lamellar (Lα) phase, there are only reverse-type aggregates with a water interior, in addn. to an essentially pure water phase, whose relative locations in the phase diagram follow the sequence (from the oil corner to the surfactant corner): reverse micellar soln. (L2), reverse anisotropic nematic (N2), reverse micellar cubic (I2), reverse hexagonal (H2), and finally, the lamellar phase. The aggregates have a finite swelling with water, and coexistence with excess water is found at higher water contents. The area per lecithin mol. was detd. in the H2 and Lα phases. This area varies with the mole ratio [H2O]/[Lec] = W0 at lower W0 values, but sats. at an area of 90 Å2/mol. for W0 ⪆ 15. The phase diagram is discussed in relation to the known formation of giant wormlike reverse micelles in the liq. L2 phase. Of particular interest here is the transition from liq. (L2) to nematic (N2) as the wormlike aggregate concn. is increased.
- 8Lehtinen, O.-P.; Nugroho, R. W. N.; Lehtimaa, T.; Vierros, S.; Hiekkataipale, P.; Ruokolainen, J.; Sammalkorpi, M.; O?sterberg, M. Effect of Temperature, Water Content and Free Fatty Acid on Reverse Micelle Formation of Phospholipids in Vegetable Oil. Colloids Surf., B 2017, 160, 355? 363, DOI: 10.1016/j.colsurfb.2017.09.050Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFKms7%252FK&md5=63cef9e605ab4626495221dd4a928f03Effect of temperature, water content and free fatty acid on reverse micelle formation of phospholipids in vegetable oilLehtinen, Olli-Pekka; Nugroho, Robertus Wahyu N.; Lehtimaa, Tuula; Vierros, Sampsa; Hiekkataipale, Panu; Ruokolainen, Janne; Sammalkorpi, Maria; Osterberg, MonikaColloids and Surfaces, B: Biointerfaces (2017), 160 (), 355-363CODEN: CSBBEQ; ISSN:0927-7765. (Elsevier B.V.)The self-assembly of phospholipids in oil, specifically lecithin in rapeseed oil, was investigated by combining exptl. and computational methods The influence of temp., water, and free fatty acids on the onset of lecithin aggregation in the rapeseed oil was detd. using the 7,7,8,8 -tetracyanoquinodimethane dye (TCNQ) solubilization method and the size and shape of the self-assembled lecithin structures were investigated by small-angle X-ray scattering and cryogenic transmission electron microscopy. In the absence of excess water in the system (0.03 wt-% water in oil), stable cylindrical lecithin reverse micelles were obsd. above the crit. micelle concn. (CMC). Comparing the aggregation response in room temp. and at 70 °C revealed that CMC decreased with increasing temp. Furthermore, already a modest amt. of added water (0.3 wt-% water in oil) was sufficient to induce the formation of lamellar lecithin structures, that phase sepd. from the oil. In low water content, oleic acid suppressed the formation of lecithin reverse micelles whereas in the presence of more water, the oleic acid stabilized the reverse micelles. Consequently, more water was needed to induce phase sepn. in the presence of oleic acid. Mol. dynamics simulations indicated that the stabilizing effect of oleic acid resulted from oleic acid enhancing phospholipid solubilization in the oil by forming a solvating shell around the phosphate head group. The findings showed that the response of the mixed surfactant system is a delicate interplay of the different components and variables. The significance of the observations is that multiple parameters need to be controlled for desired system response, for example towards vegetable oil purifn. or phospholipid based microemulsions.
- 9Lei, L.; Ma, Y.; Kodali, D. R.; Liang, J.; Davis, H. T. Ternary Phase Diagram of Soybean Phosphatidylcholine-Water-Soybean Oil and Its Application to the Water Degumming Process. J. Am. Oil Chem. Soc. 2003, 80, 383? 388, DOI: 10.1007/s11746-003-0708-yGoogle Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjslGmu74%253D&md5=1f19c6b2a7d4897aaa782a8e3d8942a0Ternary phase diagram of soybean phosphatidylcholine-water-soybean oil and its application to the water degumming processLei, Ling; Ma, Yue; Kodali, Dharma R.; Liang, Jingmei; Davis, H. TedJournal of the American Oil Chemists' Society (2003), 80 (4), 383-388CODEN: JAOCA7; ISSN:0003-021X. (AOCS Press)Crude soybean oil contains phospholipids (2.5 wt%) that must be removed from oil during processing. A common method is the water-degumming process. A ternary phase diagram of soybean oil-water-soybean PC, a major component of phospholipids, was established. From this diagram, phase transitions and compns. of phases can be detd. A theor. model describing the relationship between aggregation curvature and the amt. of water added is presented to explain the phase transitions. The amt. of water absorption by the lamellar phase should be larger than the crit. value of 34 wt% based on the total wt. of water and PC. Below this crit. amt., phospholipids tend to form liposomes. Above the crit. point and below the satn. point, larger aggregates of particles form and can be easily sepd. When more water is added to reach the water adsorption limit, about 40 wt% based on the total wt. of water and PC, a phase transition boundary is obsd., beyond which a third phase, water, appears and the particle size falls dramatically. In between the crit. line predicted by the model and the water adsorption satn. line obsd. exptl., there is an operation window on the ternary phase diagram for the water-degumming process.
- 10Njauw, C.-W.; Cheng, C.-Y.; Ivanov, V. A.; Khokhlov, A. R.; Tung, S.-H. Molecular Interactions between Lecithin and Bile Salts/Acids in Oils and Their Effects on Reverse Micellization. Langmuir 2013, 29, 3879? 3888, DOI: 10.1021/la304601pGoogle Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjtVCgu7g%253D&md5=a6f4a3f90f90894f0c84938c93d88142Molecular Interactions between Lecithin and Bile Salts/Acids in Oils and Their Effects on Reverse MicellizationNjauw, Ching-Wei; Cheng, Chih-Yang; Ivanov, Viktor A.; Khokhlov, Alexei R.; Tung, Shih-HuangLangmuir (2013), 29 (12), 3879-3888CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The addn. of bile salts to lecithin organosols induces the formation of reverse wormlike micelles and that the worms are similar to long polymer chains that entangle each other to form viscoelastic solns. The authors further studied the effects of different bile salts and bile acids on the growth of lecithin reverse worms in cyclohexane and n-decane. The authors used rheol. and small-angle scattering techniques to analyze the properties and structures of the reverse micelles. All of the bile salts can transform the originally spherical lecithin reverse micelles into wormlike micelles and their rheol. behaviors can be described by the single-relaxation-time Maxwell model. However, their efficiencies to induce the worms are different. In contrast, before phase sepn., bile acids can induce only short cylindrical micelles that are not long enough to impart viscoelasticity. FTIR spectroscopy was used to study the interactions between lecithin and bile salts/acids and found that different bile salts/acids employ different functional groups to form hydrogen bonds with lecithin. Such effects det. the relative positions of the bile salts/acids in the headgroups of lecithin, thus resulting in varying efficiencies to alter the effective crit. packing parameter for the formation of wormlike micelles. This work highlights the importance of intermol. interactions in mol. self-assembly.
- 11Schurtenberger, P.; Jerke, G.; Cavaco, C.; Pedersen, J. S. Cross-Section Structure of Cylindrical and Polymer-like Micelles from Small-Angle Scattering Data. 2. Experimental Results. Langmuir 1996, 12, 2433? 2440, DOI: 10.1021/la9507444Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XisFCnt74%253D&md5=98e550c49216e6bed73d7d21fc54bd69Cross-Section Structure of Cylindrical and Polymer-like Micelles from Small-Angle Scattering Data. 2. Experimental ResultsSchurtenberger, Peter; Jerke, Goetz; Cavaco, Carolina; Pedersen, Jan SkovLangmuir (1996), 12 (10), 2433-40CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)We report a small-angle neutron scattering (SANS) study of the cross-section structure of polymer-like lecithin reverse micelles in deuterated cyclohexane. We demonstrate that the application of the indirect Fourier transformation and square-root deconvolution methods to data from SANS measurements with cylindrical polymer-like micelles allows for a direct verification of the previously postulated geometrical model of flexible tubular structures with a well defined water core and a surfactant shell. By combining contrast variation expts. and data anal. performed on an abs. scale, we quant. deduce information on properties such as the extension of the aq. core and the degree of water penetration into the headgroup and solvent penetration into the tail region.
- 12Sugiura, S.; Ichikawa, S.; Sano, Y.; Nakajima, M.; Liu, X. Q.; Seki, M.; Furusaki, S. Formation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty Acids. J. Colloid Interface Sci. 2001, 240, 566? 572, DOI: 10.1006/jcis.2001.7703Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXlsFGqt7w%253D&md5=88be65bdd1180a9ee65f0aa5c561007cFormation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty AcidsSugiura, Shinji; Ichikawa, Sosaku; Sano, Yoh; Nakajima, Mitsutoshi; Liu, Xin Qi; Seki, Minoru; Furusaki, ShintaroJournal of Colloid and Interface Science (2001), 240 (2), 566-572CODEN: JCISA5; ISSN:0021-9797. (Academic Press)The formation of reversed micellar systems composed of phosphatidylcholine (PC) and fatty acid was newly demonstrated by a significant increase in H2O content in the org. Et oleate phase when the micelles were prepd. by the contact method. The solubilized H2O concn. in the reversed micellar org. phase reached 3%. The new systems are expected to be used as highly biocompatible reversed micellar systems. The structure of the reversed micelles composed of PC and oleic acid was characterized by detg. the H2O concn. and by small-angle x-ray scattering anal. The reversed micelles composed of PC and oleic acid formed in Et oleate were spherical. The radius of gyration was 30-50 Å. The size of the reversed micelles decreased with an increase in the oleic acid concn. and was independent of the PC concn. Exptl. results indicated that the structure of the reversed micellar system was detd. by the oleic acid concn. An increase in the PC concn. caused an increase in the no. of reversed micelles of the same size. These reversed micellar systems are expected to be used as solubilization media in pharmaceutical and food industries because they are not toxic. (c) 2001 Academic Press.
- 13Tung, S.-H.; Huang, Y.-E.; Raghavan, S. R. A New Reverse Wormlike Micellar System: Mixtures of Bile Salt and Lecithin in Organic Liquids. J. Am. Chem. Soc. 2006, 128, 5751? 5756, DOI: 10.1021/ja0583766Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjt1yitbk%253D&md5=3bd2efb9a7bf2307d705009d5bf26d37A New Reverse Wormlike Micellar System: Mixtures of Bile Salt and Lecithin in Organic LiquidsTung, Shih-Huang; Huang, Yi-En; Raghavan, Srinivasa R.Journal of the American Chemical Society (2006), 128 (17), 5751-5756CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report a new route for forming reverse wormlike micelles (i.e., long, flexible micellar chains) in nonpolar org. liqs. such as cyclohexane and n-decane. This route involves the addn. of a bile salt (e.g., sodium deoxycholate) in trace amts. to solns. of the phospholipid lecithin. Previous recipes for reverse wormlike micelles have usually required the addn. of water to induce reverse micellar growth; here, we show that bile salts, due to their unique "facially amphiphilic" structure, can play a role analogous to that of water and promote the longitudinal aggregation of lecithin mols. into reverse micellar chains. The formation of transient entangled networks of these reverse micelles transforms low-viscosity lecithin organosols into strongly viscoelastic fluids. The zero-shear viscosity increases by more than 5 orders of magnitude, and it is the molar ratio of bile salt to lecithin that controls the viscosity enhancement. The growth of reverse wormlike micelles is also confirmed by small-angle neutron scattering (SANS) expts. on these fluids.
- 14Zhao, Y.; Zhang, J.; Wang, Q.; Li, W.; Li, J.; Han, B.; Wu, Z.; Zhang, K.; Li, Z. Cylindrical-to-Spherical Shape Transformation of Lecithin Reverse Micelles Induced by CO2. Langmuir 2010, 26, 4581? 4585, DOI: 10.1021/la904917nGoogle Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivV2mur8%253D&md5=91fea3f110d05d178f6771db5c280cc8Cylindrical-to-Spherical Shape Transformation of Lecithin Reverse Micelles Induced by CO2Zhao, Yueju; Zhang, Jianling; Wang, Qian; Li, Wei; Li, Jianshen; Han, Buxing; Wu, Zhonghua; Zhang, Kunhao; Li, ZhihongLangmuir (2010), 26 (7), 4581-4585CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The effect of CO2 on the microstructure of L-α-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO2 could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform IR (FT-IR) and UV-vis techniques were also utilized to investigate intermol. interactions and micropolarity in the reverse micelles at different CO2 pressures. The redn. of the degree of hydrogen bonding between surfactant headgroups and water with added CO2 was found to be the main reason for the micellar shape transformation. In the absence of CO2, the hydrogen bonding between water and P[n.58875]O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO2 to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO2-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO2, and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO2. This method of tuning micellar shape has many advantages compared to traditional methods.
- 15Vierros, S.; Sammalkorpi, M. Phosphatidylcholine Reverse Micelles on the Wrong Track in Molecular Dynamics Simulations of Phospholipids in an Organic Solvent. J. Chem. Phys. 2015, 142, 094902, DOI: 10.1063/1.4914022Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjvF2itLs%253D&md5=3f18514f9198ba8707a04fcc3adb5863Phosphatidylcholine reverse micelles on the wrong track in molecular dynamics simulations of phospholipids in an organic solventVierros, S.; Sammalkorpi, M.Journal of Chemical Physics (2015), 142 (9), 094902/1-094902/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)Here, we examine a well-characterized model system of phospholipids in cyclohexane via mol. dynamics simulations using a force field known for reproducing both phospholipid behavior in water and cyclohexane bulk properties to a high accuracy, CHARMM36, with the aim of evaluating the transferability of a force field parametrization from an aq. environment to an org. solvent. We compare the resulting reverse micelles with their expected exptl. shape and size, and find the model struggles with reproducing basic, exptl. known reverse micellar structural characteristics for common phosphadidylcholine lipids such as 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dioleyl-sn-glycero-3-phosphatidylcholine (DOPC), and 1,2-dilinoleyl-sn-glycero-3-phosphatidylcholine (DLPC) in cyclohexane solvent. We find evidence that the deviation from the exptl. behavior originates from an underestimation of the lipid tail-cyclohexane interaction in the model. We compensate for this, obtain reverse micellar structures within the exptl. expected range, and characterize these structurally in mol. detail. Our findings indicate extra caution and verification of model applicability is warranted in simulational studies employing std. biomol. models outside the usual aq. environment. (c) 2015 American Institute of Physics.
- 16Vierros, S.; Sammalkorpi, M. Role of Hydration in Phosphatidylcholine Reverse Micelle Structure and Gelation in Cyclohexane: A Molecular Dynamics Study. Phys. Chem. Chem. Phys. 2015, 17, 14951? 14960, DOI: 10.1039/C5CP01799HGoogle Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXotFClt7w%253D&md5=879e253bf0e6b0ca41860167d819952fRole of hydration in phosphatidylcholine reverse micelle structure and gelation in cyclohexane: a molecular dynamics studyVierros, S.; Sammalkorpi, M.Physical Chemistry Chemical Physics (2015), 17 (22), 14951-14960CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)In this work, we employ all-atom mol. dynamics simulations to examine the hydration response of phospholipid reverse micelles in cyclohexane. This ternary phospholipid-water-cyclohexane system is an important organogel forming system and the focus of this study is on gaining insight on the factors governing the gelation transition. We map the contributions rising from specific lipid-lipid and lipid-water interactions, and their response to increasing aggregate size and changes in water-to-lipid ratio. We find that, opposed to phospholipid-heptane organogels, in cyclohexane, lipid bridging and hydrogen bond driven stabilization of the lipid head group packing is at minor role in dictating the reverse micelle structural transitions corresponding to the organosol-organogel phase transition in this system. Instead, increasing the lipid head hydration changes the lipid packing factor directly which leads to gelation through the formation of long, wormlike micelles. Furthermore, the confined environment in the reverse micellar cores slows down the water dynamics significantly in comparison to fully hydrated phospholipid bilayers and at low water-to-lipid ratios this slow-down is even more significant. The findings map the role of hydration at microscopic level in these systems and could enable tailoring reverse micellar systems for applications relying on the structure and dynamics of the reverse micelles. Examples include such as drug transport, nanotemplating, or confined chem. in the reverse micelle core water space, e.g., in catalysis.
- 17Abel, S.; Galamba, N.; Karakas, E.; Marchi, M.; Thompson, W. H.; Laage, D. On the Structural and Dynamical Properties of DOPC Reverse Micelles. Langmuir 2016, 32, 10610? 10620, DOI: 10.1021/acs.langmuir.6b02566Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFCms7vL&md5=b14c15e66eea9f096fe1f2d5503ea814On the Structural and Dynamical Properties of DOPC Reverse MicellesAbel, Stephane; Galamba, Nuno; Karakas, Esra; Marchi, Massimo; Thompson, Ward H.; Laage, DamienLangmuir (2016), 32 (41), 10610-10620CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The structure and dynamics of phospholipid reverse micelles are studied by mol. dynamics. We report all-atom unconstrained simulations of 1,2-dioleoyl-sn-phosphatidylcholine (DOPC) reverse micelles in benzene of increasing sizes, with water-to-surfactant no. ratios ranging from W0 = 1 to 16. The aggregation no., i.e., the no. of DOPC mols. per reverse micelle, is detd. to fit exptl. light-scattering measurements of the reverse micelle diam. The simulated reverse micelles are found to be approx. spherical. Larger reverse micelles (W0 > 4) exhibit a layered structure with a water core and the hydration structure of DOPC phosphate head groups is similar to that found in phospholipid membranes. In contrast, the structure of smaller reverse micelles (W0 ≤ 4) cannot be described as a series of concentric layers successively contg. water, surfactant head groups, and surfactant tails, and the head groups are only partly hydrated and frequently present in the core. The dynamics of water mols. within the phospholipid reverse micelles slow down as the reverse micelle size decreases, in agreement with prior studies on AOT and Igepal reverse micelles. However, the av. water reorientation dynamics in DOPC reverse micelles is found to be much slower than in AOT and Igepal reverse micelles with the same W0 ratio. This is explained by the smaller water pool and by the stronger interactions between water and the charged head groups, as confirmed by the red-shift of the computed IR line shape with decreasing W0.
- 18Chatzidaki, M. D.; Papavasileiou, K. D.; Papadopoulos, M. G.; Xenakis, A. Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics Study. Langmuir 2017, 33, 5077? 5085, DOI: 10.1021/acs.langmuir.7b00213Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXntlWisL4%253D&md5=6d6fd9ef8cf0ea417d1e5d42e7796a06Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics StudyChatzidaki, Maria D.; Papavasileiou, Konstantinos D.; Papadopoulos, Manthos G.; Xenakis, AristotelisLangmuir (2017), 33 (20), 5077-5085CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Water-in-oil microemulsions with biocompatible components were formulated to be used as carriers of natural antioxidants, such as hydroxytyrosol (HT) and gallic acid (GA). The system was composed of a mixt. of natural surfactants, lecithin and monoglycerides, medium chain triglycerides, and aq. phase. A dual approach was undertaken to study the structure and dynamics of these complicated systems. First, exptl. data were collected by using adequate techniques, such as dynamic light scattering (DLS) and ESR spectroscopy. Following this, a coarse-grained mol. dynamics (CGMD) study based on the exptl. compn. using the MARTINI force field was conducted. The simulations revealed the spontaneous formation of reverse micelles (RMs) starting from completely random initial conformations, underlying their enhanced thermodn. stability. The location of the bioactive mols., as well as the structure of the RM, were in accordance with the exptl. findings. Furthermore, GA mols. were found to be located inside the water core, in contrast to the HT ones, which seem to lie at the surfactant interfacial layer. The difference in the antioxidants' mol. location was only revealed in detail from the computational anal. and explains the RM's swelling obsd. by GA in DLS measurements.
- 19Vierros, S.; O?sterberg, M.; Sammalkorpi, M. Aggregation Response of Triglyceride Hydrolysis Products in Cyclohexane and Triolein. Phys. Chem. Chem. Phys. 2018, 20, 27192? 27204, DOI: 10.1039/C8CP05104FGoogle Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvV2ju7bJ&md5=1714eea3920c1d56b9fb5a3cac827d66Aggregation response of triglyceride hydrolysis products in cyclohexane and trioleinVierros, Sampsa; Osterberg, Monika; Sammalkorpi, MariaPhysical Chemistry Chemical Physics (2018), 20 (42), 27192-27204CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Here, we examine the aggregation response of a series of triglyceride-based biosurfactants in cyclohexane and triglyceride solvents via all-atom mol. dynamics simulations and supporting expts. The surfactant aggregation follows in all systems, with only minor deviations, a multiple equil., i.e. open assocn., model. Monoglyceride aggregation in cyclohexane exhibits a crit. micellization concn., cmc, showing a cmc can exist even in a system following open assocn. However, the cmc is assocd. with a change in balance with oligomeric and larger aggregates in the soln., not an onset of aggregate formation. It is demonstrated that reverse micelles can form in the absence of water stabilized by intersurfactant hydrogen bonds alone, and that the polarity and hydrogen bonding capability of triolein systematically reduces surfactant aggregation in comparison to cyclohexane. A comparison between CHARMM27 and CHARMM36 simulation models reveals that while trends are preserved, the models differ in quant. prediction. Finally, consolidation of the general aggregation response trends predicted by the modeling are obtained via 7,7,8,8-tetracyanoquinodimethane dye (TCNQ) solubilization expts. on the corresponding model plant oil systems. The findings provide guidelines for predicting and controlling surfactant aggregation response in org. solvents via tuning the solvent polarity and hydrogen bonding ability, and a crit. assessment of simulation and aggregation models for surfactant systems in org. solvents.
- 20Issariyakul, T.; Dalai, A. K. Biodiesel from Vegetable Oils. Renewable Sustainable Energy Rev. 2014, 31, 446? 471, DOI: 10.1016/j.rser.2013.11.001Google Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXivVCqur4%253D&md5=bb39a95aafd2efe00617a593f0698430Biodiesel from vegetable oilsIssariyakul, Titipong; Dalai, Ajay K.Renewable & Sustainable Energy Reviews (2014), 31 (), 446-471CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)A review. Biodiesel is gaining acceptance in the market as fuel and lubricant. It is expected that biodiesel industries will rapidly grow worldwide in the coming years and information on biodiesel feedstock, prodn., and characteristics will be crucial than ever esp. for those using vegetable oils as feedstock as these are currently the major sources for making biodiesel. In the present paper, a comprehensive review is reported on feedstock, prodn. technologies, and characteristics of biodiesel. More specifically, selected available vegetable oils are explored as feedstock for biodiesel prodn. Prodn. technologies including latest catalyst developments are discussed. Finally, biodiesel characteristics and parameters influencing the corresponding properties are revealed. Since this paper covers a wide range in biodiesel area, it serves as a general public education medium as well as a research ref. for biodiesel prodn. from vegetable oils.
- 21Xenakis, A.; Papadimitriou, V.; Sotiroudis, T. G. Colloidal Structures in Natural Oils. Curr. Opin. Colloid Interface Sci. 2010, 15, 55? 60, DOI: 10.1016/j.cocis.2009.11.007Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhvFeku74%253D&md5=b6f1427b6ab0c0c54bef526d280eaa67Colloidal structures in natural oilsXenakis, Aristotelis; Papadimitriou, Vassiliki; Sotiroudis, Theodore G.Current Opinion in Colloid & Interface Science (2010), 15 (1-2), 55-60CODEN: COCSFL; ISSN:1359-0294. (Elsevier B.V.)A review. Natural oils are in general mixts. of triglycerides of various fatty acids contg. also small quantities of a multitude of other mols., the minor components. Their compn. depends on the type of their sources, either vegetable or animal, and on agronomic and climatic conditions. Extn. process highly influences the final compn. of the natural oils. The bulk triglyceride phase presents some structural order due to the internal polarity of these mols. The presence of the minor components, which are either amphiphilic or even hydrophilic together with some remaining moisture, induces colloidal assocn. within the lipophilic triglyceride phase. These local organizates host proteins and antioxidants that preserve their activity influencing the quality and stability of the edible oils. Of specific interest is the case of the veiled virgin olive oil, the untreated juice of the olives. Veiled virgin olive oil is unique among vegetable oils that is consumed without any refining process and consequently possesses colloidal structure. It is remarkable that this unfiltered oil presents higher resistance to oxidn. than the filtered ones, indicating the significance of internal structure to the final quality of the product.
- 22Boesecke, P. Reduction of Two-dimensional Small- and Wide-angle X-ray Scattering Data. J. Appl. Crystallogr. 2007, 40, s423? s427, DOI: 10.1107/S0021889807001100Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvVOhsr0%253D&md5=bf83c742c34db7a003bfc4569aadb3c5Reduction of two-dimensional small- and wide-angle x-ray scattering dataBoesecke, PeterJournal of Applied Crystallography (2007), 40 (S1), s423-s427CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)At the beamlines ID01 and ID02 of the European Synchrotron Radiation Facility in Grenoble, France, position-sensitive detectors for time-resolved small- and wide-angle x-ray scattering expts. are in use. The applied data redn. method has never been described comprehensively. This article outlines the parametrization of the raw data and introduces the programs developed for this purpose. Data redn. in the sense of this article means all steps between detector readout and normalization to abs. scattering intensities. This includes all corrections that can be made without any specific knowledge of the sample, e.g. detector dark-image correction, division by a flat-field and intensity normalization. Processed data are either two- or one-dimensional. Optionally, statistical errors can be propagated through the calcns.
- 23Orthaber, D.; Bergmann, A.; Glatter, O. SAXS Experiments on Absolute Scale with Kratky Systems Using Water As a Secondary Standard. J. Appl. Crystallogr. 2000, 33, 218? 225, DOI: 10.1107/S0021889899015216Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXivVaqurw%253D&md5=e36ee06d05cb163dac3647f2f71e127fSAXS experiments on absolute scale with Kratky systems using water as a secondary standardOrthaber, Doris; Bergmann, Alexander; Glatter, OttoJournal of Applied Crystallography (2000), 33 (2), 218-225CODEN: JACGAR; ISSN:0021-8898. (Munksgaard International Publishers Ltd.)For small-angle scattering, of x-rays (SAXS) and neutrons (SANS), the importance of abs. calibration was recognized since the inception of the technique. The work reported here focuses on SAXS measurements using Kratky slit systems. In former days, only mol. wts. or scattering per particle were detd., but today abs. calibration implies the use of the unit of cm-1 for the scattering curve. It is necessary to measure the so-called abs. intensity, which is the ratio of the scattering intensity to the primary intensity P0. Basically there are 2 possible ways to det. the abs. intensity. The 1st 1 is the direct method, which involves the mech. attenuation of the primary beam by a rotating disk or a moving slit. The 2nd is the indirect method, using secondary stds. H2O is well suited as a calibration std. because of the angle-independent scattering. The essential advantage is that the scattering of H2O only depends on the phys. property of isothermal compressibility. Before presenting an example of the practical performance of this method, the most important theor. equations for an SAS expt. on the abs. scale are summarized. With the slit collimation system, the scattering curve of H2O can be measured with high enough statistical accuracy. As a 1st example, the scattering curve of the protein lysozyme on the abs. scale is presented. The 2nd example is the detn. of the aggregation no. of a triblock copolymer P94 (EO17-PO42-EO17). Taking into account that at least 10% of the polymer sample consists of diblocks, the accuracy of ∼10% for the detd. aggregation no. is rather good. The data of P94 are considered on the particle scale to obtain the radial scattering-length d. distribution.
- 24Pedersen, J. S. Analysis of Small-Angle Scattering Data from Colloids and Polymer Solutions: Modeling and Least-squares Fitting. Adv. Colloid Interface Sci. 1997, 70, 171? 210, DOI: 10.1016/S0001-8686(97)00312-6Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvVSkt7Y%253D&md5=4422d69ed5b3845a00b2fc27fc3d8f8bAnalysis of small-angle scattering data from colloids and polymer solutions: modeling and least-squares fittingPedersen, Jan SkovAdvances in Colloid and Interface Science (1997), 70 (), 171-210CODEN: ACISB9; ISSN:0001-8686. (Elsevier)Anal. and modeling of small-angle scattering data from systems consisting of colloidal particles or polymers in soln. are discussed. A review with 95 refs.; the anal. requires application of least-squares methods; the basic principles of linear and nonlinear least-squares methods are summarized with emphasis on applications in anal. of small-angle scattering data. These include indirect Fourier transformation, square-root deconvolution, size distribution detns., and modeling. The inclusion of corrections for instrumental smearing effects is discussed. The most common anal. expressions for model form factors and structure factors are summarized. An example of anal. of small-angle neutron and x-ray scattering data for block copolymer micelles is given.
- 25Abraham, M. J.; Murtola, T.; Schulz, R.; Pa?ll, S.; Smith, J. C.; Hess, B.; Lindahl, E. GROMACS: High Performance Molecular Simulations through Multi-level Parallelism from Laptops to Supercomputers. SoftwareX 2015, 1?2, 19? 25, DOI: 10.1016/j.softx.2015.06.001Google ScholarThere is no corresponding record for this reference.
- 26MacKerell, A. D. All-atom Empirical Potential for Molecular Modeling and Dynamics Studies of Proteins. J. Phys. Chem. B 1998, 102, 3586? 3616, DOI: 10.1021/jp973084fGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXivVOlsb4%253D&md5=ebb5100dafd0daeee60ca2fa66c1324aAll-Atom Empirical Potential for Molecular Modeling and Dynamics Studies of ProteinsMacKerell, A. D., Jr.; Bashford, D.; Bellott, M.; Dunbrack, R. L.; Evanseck, J. D.; Field, M. J.; Fischer, S.; Gao, J.; Guo, H.; Ha, S.; Joseph-McCarthy, D.; Kuchnir, L.; Kuczera, K.; Lau, F. T. K.; Mattos, C.; Michnick, S.; Ngo, T.; Nguyen, D. T.; Prodhom, B.; Reiher, W. E., III; Roux, B.; Schlenkrich, M.; Smith, J. C.; Stote, R.; Straub, J.; Watanabe, M.; Wiorkiewicz-Kuczera, J.; Yin, D.; Karplus, M.Journal of Physical Chemistry B (1998), 102 (18), 3586-3616CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)New protein parameters are reported for the all-atom empirical energy function in the CHARMM program. The parameter evaluation was based on a self-consistent approach designed to achieve a balance between the internal (bonding) and interaction (nonbonding) terms of the force field and among the solvent-solvent, solvent-solute, and solute-solute interactions. Optimization of the internal parameters used exptl. gas-phase geometries, vibrational spectra, and torsional energy surfaces supplemented with ab initio results. The peptide backbone bonding parameters were optimized with respect to data for N-methylacetamide and the alanine dipeptide. The interaction parameters, particularly the at. charges, were detd. by fitting ab initio interaction energies and geometries of complexes between water and model compds. that represented the backbone and the various side chains. In addn., dipole moments, exptl. heats and free energies of vaporization, solvation and sublimation, mol. vols., and crystal pressures and structures were used in the optimization. The resulting protein parameters were tested by applying them to noncyclic tripeptide crystals, cyclic peptide crystals, and the proteins crambin, bovine pancreatic trypsin inhibitor, and carbonmonoxy myoglobin in vacuo and in a crystal. A detailed anal. of the relationship between the alanine dipeptide potential energy surface and calcd. protein φ, χ angles was made and used in optimizing the peptide group torsional parameters. The results demonstrate that use of ab initio structural and energetic data by themselves are not sufficient to obtain an adequate backbone representation for peptides and proteins in soln. and in crystals. Extensive comparisons between mol. dynamics simulation and exptl. data for polypeptides and proteins were performed for both structural and dynamic properties. Calcd. data from energy minimization and dynamics simulations for crystals demonstrate that the latter are needed to obtain meaningful comparisons with exptl. crystal structures. The presented parameters, in combination with the previously published CHARMM all-atom parameters for nucleic acids and lipids, provide a consistent set for condensed-phase simulations of a wide variety of mols. of biol. interest.
- 27Scholfield, C. R.; Dutton, H. J.; Dimler, R. J. Carbohydrate Constituents of Soybean ?Lecithin. J. Am. Oil Chem. Soc. 1952, 29, 293? 298, DOI: 10.1007/BF02631478Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG38Xlt1Srug%253D%253D&md5=88350a98fd1bc1e3b850ca3b5e8495e0Carbohydrate constituents of soybean "lecithin."Scholfield, C. R.; Dutton, Herbert J.; Dimler, Robert J.Journal of the American Oil Chemists' Society (1952), 29 (), 293-8CODEN: JAOCA7; ISSN:0003-021X.Both free and bound sugars in soybean lecithin were identified by means of paper chromatography along with an estimate of the amts. of each sugar in one sample. The free sugars were those remaining with the phosphatides after extn. with 50% alc. The free sugars consist mainly of sucrose and stachyose with a smaller amt. of raffinose. The greater part of the bound sugars are found with a phosphoinositide fraction which is more sol. in hexane; these sugars consist of galactose, mannose, and arabinose. Arabinose is freed by mild hydrolysis and all 3 by refluxing with 2 N H2SO4. The same 3 sugars, together with a smaller amt. of an unidentified sugar, are found in the corresponding fraction of corn phosphatides. In the abs. alc.-sol. fractions of both soybean and corn phosphatides the bound sugars consist of glucose and galactose.
- 28Feller, S. E.; MacKerell, A. D. An Improved Empirical Potential Energy Function for Molecular Simulations of Phospholipids. J. Phys. Chem. B 2000, 104, 7510? 7515, DOI: 10.1021/jp0007843Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXkvVWgtL4%253D&md5=cc7ce005f161c8a2bbe7ffd674754c8eAn Improved Empirical Potential Energy Function for Molecular Simulations of PhospholipidsFeller, Scott E.; MacKerell, Alexander D. ,Jr.Journal of Physical Chemistry B (2000), 104 (31), 7510-7515CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)Improvements in the CHARMM all-atom force field for at.-level mol. simulations of lipids are reported. Substantial adjustments have been made to the Lennard-Jones (LJ) hydrocarbon and torsional parameters and to the partial at. charges and torsional parameters of the phosphate moiety. These changes were motivated by a combination of unexpected simulation results and recent high-level ab initio quantum mech. calcns. The parameter optimization procedure is described, and the resulting energy function validated by an 11 ns mol. dynamics simulation of a hydrated phospholipid bilayer. Of note is the influence of the hydrocarbon LJ parameters on the conformational properties of the aliph. tails, emphasizing the importance of obtaining the proper balance between the bonded and nonbonded portions of the force field. Compatibility with the CHARMM all-atom parameter sets for proteins and nucleic acids has been maintained such that high quality simulations of biol. interesting membranes are possible. The complete force field is included as Supporting Information and is available from www.pharmacy.umaryland.edu/∼alex.
- 29Bjelkmar, P.; Larsson, P.; Cuendet, M. A.; Hess, B.; Lindahl, E. Implementation of the CHARMM Force Field in GROMACS: Analysis of Protein Stability Effects from Correction Maps, Virtual Interaction Sites, and Water Models. J. Chem. Theory Comput. 2010, 6, 459? 466, DOI: 10.1021/ct900549rGoogle Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptlKhsw%253D%253D&md5=728be20d72ab18e98268c1a48efcdcb1Implementation of the CHARMM Force Field in GROMACS: Analysis of Protein Stability Effects from Correction Maps, Virtual Interaction Sites, and Water ModelsBjelkmar, Par; Larsson, Per; Cuendet, Michel A.; Hess, Berk; Lindahl, ErikJournal of Chemical Theory and Computation (2010), 6 (2), 459-466CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)CHARMM27 is a widespread and popular force field for biomol. simulation, and several recent algorithms such as implicit solvent models have been developed specifically for it. The authors have here implemented the CHARMM force field and all necessary extended functional forms in the GROMACS mol. simulation package, to make CHARMM-specific features available and to test them in combination with techniques for extended time steps, to make all major force fields available for comparison studies in GROMACS, and to test various solvent model optimizations, in particular the effect of Lennard-Jones interactions on hydrogens. The implementation has full support both for CHARMM-specific features such as multiple potentials over the same dihedral angle and the grid-based energy correction map on the .vphi., ψ protein backbone dihedrals, as well as all GROMACS features such as virtual hydrogen interaction sites that enable 5 fs time steps. The medium-to-long time effects of both the correction maps and virtual sites have been tested by performing a series of 100 ns simulations using different models for water representation, including comparisons between CHARMM and traditional TIP3P. Including the correction maps improves sampling of near native-state conformations in the authors' systems, and to some extent it is even able to refine distorted protein conformations. Finally, the authors show that this accuracy is largely maintained with a new implicit solvent implementation that works with virtual interaction sites, which enables performance in excess of 250 ns/day for a 900-atom protein on a quad-core desktop computer.
- 30He?nin, J.; Shinoda, W.; Klein, M. L. United-atom Acyl Chains for CHARMM Phospholipids. J. Phys. Chem. B 2008, 112, 7008? 7015, DOI: 10.1021/jp800687pGoogle ScholarThere is no corresponding record for this reference.
- 31Jo, S.; Song, K. C.; Desaire, H.; MacKerell, A. D., Jr.; Im, W. Glycan Reader: Automated Sugar Identification and Simulation Preparation for Carbohydrates and Glycoproteins. J. Comput. Chem. 2011, 32, 3135? 3141, DOI: 10.1002/jcc.21886Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpvVamtrk%253D&md5=0cd04c0fb892d58ae69501f23ab079dfGlycan Reader: Automated sugar identification and simulation preparation for carbohydrates and glycoproteinsJo, Sunhwan; Song, Kevin C.; Desaire, Heather; MacKerell, Alexander D.; Im, WonpilJournal of Computational Chemistry (2011), 32 (14), 3135-3141CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)Understanding how glycosylation affects protein structure, dynamics, and function is an emerging and challenging problem in biol. As a first step toward glycan modeling in the context of structural glycobiol., the authors have developed Glycan Reader and integrated it into the CHARMM-GUI,. Glycan Reader greatly simplifies the reading of PDB structure files contg. glycans through (i) detection of carbohydrate mols., (ii) automatic annotation of carbohydrates based on their three-dimensional structures, (iii) recognition of glycosidic linkages between carbohydrates as well as N-/O-glycosidic linkages to proteins, and (iv) generation of inputs for the biomol. simulation program CHARMM with the proper glycosidic linkage setup. In addn., Glycan Reader is linked to other functional modules in CHARMM-GUI, allowing users to easily generate carbohydrate or glycoprotein mol. simulation systems in soln. or membrane environments and visualize the electrostatic potential on glycoprotein surfaces. These tools are useful for studying the impact of glycosylation on protein structure and dynamics. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011.
- 32Park, S.-J.; Lee, J.; Patel, D. S.; Ma, H.; Lee, H. S.; Jo, S.; Im, W. Glycan Reader Is Improved to Recognize Most Sugar Types and Chemical Modifications in the Protein Data Bank. Bioinformatics 2017, 33, 3051? 3057, DOI: 10.1093/bioinformatics/btx358Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvFGju7bO&md5=16900496c68d5ffeedb08ed0e67e0b94Glycan Reader is improved to recognize most sugar types and chemical modifications in the Protein Data BankPark, Sang-Jun; Lee, Jumin; Patel, Dhilon S.; Ma, Hongjing; Lee, Hui Sun; Jo, Sunhwan; Im, WonpilBioinformatics (2017), 33 (19), 3051-3057CODEN: BOINFP; ISSN:1367-4811. (Oxford University Press)Motivation: Glycans play a central role in many essential biol. processes. Glycan Reader was originally developed to simplify the reading of Protein Data Bank (PDB) files contg. glycans through the automatic detection and annotation of sugars and glycosidic linkages between sugar units and to proteins, all based on at. coordinates and connectivity information. Carbohydrates can have various chem. modifications at different positions, making their chem. space much diverse. Unfortunately, current PDB files do not provide exact annotations for most carbohydrate derivs. and more than 50% of PDB glycan chains have at least one carbohydrate deriv. that could not be correctly recognized by the original Glycan Reader. Results: Glycan Reader has been improved and now identifies most sugar types and chem. modifications (including various glycolipids) in the PDB, and both PDB and PDBx/mmCIF formats are supported. CHARMM-GUI Glycan Reader is updated to generate the simulation system and input of various glycoconjugates with most sugar types and chem. modifications. It also offers a new functionality to edit the glycan structures through addn./deletion/modification of glycosylation types, sugar types, chem. modifications, glycosidic linkages, and anomeric states. The simulation system and input files can be used for CHARMM, NAMD, GROMACS, AMBER, GENESIS, LAMMPS, Desmond, OpenMM, and CHARMM/OpenMM. Glycan Fragment Database in GlycanStructure.Org is also updated to provide an intuitive glycan sequence search tool for complex glycan structures with various chem. modifications in the PDB.
- 33Jo, S.; Kim, T.; Iyer, V. G.; Im, W. CHARMM-GUI: A Web-based Graphical User Interface for CHARMM. J. Comput. Chem. 2008, 29, 1859? 1865, DOI: 10.1002/jcc.20945Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosVKksbc%253D&md5=112a3dd61d792b040f9f716b32220d7eCHARMM-GUI: a web-based graphical user interface for CHARMMJo, Sunhwan; Kim, Taehoon; Iyer, Vidyashankara G.; Im, WonpilJournal of Computational Chemistry (2008), 29 (11), 1859-1865CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)CHARMM is an academic research program used widely for macromol. mechanics and dynamics with versatile anal. and manipulation tools of at. coordinates and dynamics trajectories. CHARMM-GUI, http://www.charmm-gui.org, has been developed to provide a web-based graphical user interface to generate various input files and mol. systems to facilitate and standardize the usage of common and advanced simulation techniques in CHARMM. The web environment provides an ideal platform to build and validate a mol. model system in an interactive fashion such that, if a problem is found through visual inspection, one can go back to the previous setup and regenerate the whole system again. In this article, we describe the currently available functional modules of CHARMM-GUI Input Generator that form a basis for the advanced simulation techniques. Future directions of the CHARMM-GUI development project are also discussed briefly together with other features in the CHARMM-GUI website, such as Archive and Movie Gallery.
- 34Brooks, B. R. CHARMM: The Biomolecular Simulation Program. J. Comput. Chem. 2009, 30, 1545? 1614, DOI: 10.1002/jcc.21287Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXms1Ciu70%253D&md5=2c6a2be869362d7131f5aea8411c1552CHARMM: The biomolecular simulation programBrooks, B. R.; Brooks, C. L., III; Mackerell, A. D., Jr.; Nilsson, L.; Petrella, R. J.; Roux, B.; Won, Y.; Archontis, G.; Bartels, C.; Boresch, S.; Caflisch, A.; Caves, L.; Cui, Q.; Dinner, A. R.; Feig, M.; Fischer, S.; Gao, J.; Hodoscek, M.; Im, W.; Kuczera, K.; Lazaridis, T.; Ma, J.; Ovchinnikov, V.; Paci, E.; Pastor, R. W.; Post, C. B.; Pu, J. Z.; Schaefer, M.; Tidor, B.; Venable, R. M.; Woodcock, H. L.; Wu, X.; Yang, W.; York, D. M.; Karplus, M.Journal of Computational Chemistry (2009), 30 (10), 1545-1614CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)A review. CHARMM (Chem. at HARvard Mol. Mechanics) is a highly versatile and widely used mol. simulation program. It has been developed over the last three decades with a primary focus on mols. of biol. interest, including proteins, peptides, lipids, nucleic acids, carbohydrates, and small mol. ligands, as they occur in soln., crystals, and membrane environments. For the study of such systems, the program provides a large suite of computational tools that include numerous conformational and path sampling methods, free energy estimators, mol. minimization, dynamics, and anal. techniques, and model-building capabilities. The CHARMM program is applicable to problems involving a much broader class of many-particle systems. Calcns. with CHARMM can be performed using a no. of different energy functions and models, from mixed quantum mech.-mol. mech. force fields, to all-atom classical potential energy functions with explicit solvent and various boundary conditions, to implicit solvent and membrane models. The program has been ported to numerous platforms in both serial and parallel architectures. This article provides an overview of the program as it exists today with an emphasis on developments since the publication of the original CHARMM article in 1983. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009.
- 35Bussi, G.; Donadio, D.; Parrinello, M. Canonical Sampling through Velocity Rescaling. J. Chem. Phys. 2007, 126, 014101, DOI: 10.1063/1.2408420Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXosVCltg%253D%253D&md5=9c182b57bfc65bca6be23c8c76b4be77Canonical sampling through velocity rescalingBussi, Giovanni; Donadio, Davide; Parrinello, MicheleJournal of Chemical Physics (2007), 126 (1), 014101/1-014101/7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)The authors present a new mol. dynamics algorithm for sampling the canonical distribution. In this approach the velocities of all the particles are rescaled by a properly chosen random factor. The algorithm is formally justified and it is shown that, in spite of its stochastic nature, a quantity can still be defined that remains const. during the evolution. In numerical applications this quantity can be used to measure the accuracy of the sampling. The authors illustrate the properties of this new method on Lennard-Jones and TIP4P water models in the solid and liq. phases. Its performance is excellent and largely independent of the thermostat parameter also with regard to the dynamic properties.
- 36Parrinello, M.; Rahman, A. Polymorphic Transitions in Single Crystals: A New Molecular Dynamics Method. J. Appl. Phys. 1981, 52, 7182? 7190, DOI: 10.1063/1.328693Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38XislSnuw%253D%253D&md5=a0a5617389f6cabbf2a405c649aadf03Polymorphic transitions in single crystals: A new molecular dynamics methodParrinello, M.; Rahman, A.Journal of Applied Physics (1981), 52 (12), 7182-90CODEN: JAPIAU; ISSN:0021-8979.A Lagrangian formulation is introduced; it can be used to make mol. dynamics (MD) calcns. on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamic equations given by this Lagrangian. This MD technique was used to the study of structural transitions of a Ni single crystal under uniform uniaxial compressive and tensile loads. Some results regarding the stress-strain relation obtained by static calcns. are invalid at finite temp. Under compressive loading, the model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. Such a transition could perhaps be obsd. exptl. under extreme conditions of shock.
- 37Essmann, U.; Perera, L.; Berkowitz, M. L.; Darden, T.; Lee, H.; Pedersen, L. G. A Smooth Particle Mesh Ewald Method. J. Chem. Phys. 1995, 103, 8577? 8593, DOI: 10.1063/1.470117Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXptlehtrw%253D&md5=092a679dd3bee08da28df41e302383a7A smooth particle mesh Ewald methodEssmann, Ulrich; Perera, Lalith; Berkowitz, Max L.; Darden, Tom; Lee, Hsing; Pedersen, Lee G.Journal of Chemical Physics (1995), 103 (19), 8577-93CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)The previously developed particle mesh Ewald method is reformulated in terms of efficient B-spline interpolation of the structure factors. This reformulation allows a natural extension of the method to potentials of the form 1/rp with p ≥ 1. Furthermore, efficient calcn. of the virial tensor follows. Use of B-splines in the place of Lagrange interpolation leads to analytic gradients as well as a significant improvement in the accuracy. The authors demonstrate that arbitrary accuracy can be achieved, independent of system size N, at a cost that scales as N log(N). For biomol. systems with many thousands of atoms and this method permits the use of Ewald summation at a computational cost comparable to that of a simple truncation method of 10 Å or less.
- 38Hess, B.; Bekker, H.; Berendsen, H. J. C.; Fraaije, J. G. E. M. LINCS: A Linear Constraint Solver for Molecular Simulations. J. Comput. Chem. 1997, 18, 1463? 1472, DOI: 10.1002/(SICI)1096-987X(199709)18:12<1463::AID-JCC4>3.0.CO;2-HGoogle Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXlvV2nu7g%253D&md5=890f8af0d2ca1f65aa93db5a3a0bacf2LINCS: a linear constraint solver for molecular simulationsHess, Berk; Bekker, Henk; Berendsen, Herman J. C.; Fraaije, Johannes G. E. M.Journal of Computational Chemistry (1997), 18 (12), 1463-1472CODEN: JCCHDD; ISSN:0192-8651. (Wiley)We present a new LINear Constraint Solver (LINCS) for mol. simulations with bond constraints using the enzyme lysozyme and a 32-residue peptide as test systems. The algorithm is inherently stable, as the constraints themselves are reset instead of derivs. of the constraints, thereby eliminating drift. Although the derivation of the algorithm is presented in terms of matrixes, no matrix matrix multiplications are needed and only the nonzero matrix elements have to be stored, making the method useful for very large mols. At the same accuracy, the LINCS algorithm is 3-4 times faster than the SHAKE algorithm. Parallelization of the algorithm is straightforward.
- 39Miyamoto, S.; Kollman, P. A. Settle: An Analytical Version of the SHAKE and RATTLE Algorithm for Rigid Water Models. J. Comput. Chem. 1992, 13, 952? 962, DOI: 10.1002/jcc.540130805Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38Xlslykt7o%253D&md5=65da9d55c7905abeaf7708d91a09e6e4SETTLE: an analytical version of the SHAKE and RATTLE algorithm for rigid water modelsMiyamoto, Shuichi; Kollman, Peter A.Journal of Computational Chemistry (1992), 13 (8), 952-62CODEN: JCCHDD; ISSN:0192-8651.An anal. algorithm, called SETTLE, for resetting the positions and velocities to satisfy the holonomic constraints on the rigid water model is presented. This method is based on the Cartesian coordinate system and can be used in place of SHAKE and RATTLE. The authors implemented this algorithm in the SPASMS package of mol. mechanics and dynamics. Several series of mol. dynamics simulations were carried out to examine the performance of the new algorithm in comparison with the original RATTLE method. SETTLE is of higher accuracy and is faster than RATTLE with reasonable tolerances by three to nine times on a scalar machine. The performance improvement ranged from factors of 26 to 98 on a vector machine since the method presented is not iterative.
- 40Marti?nez, L.; Andrade, R.; Birgin, E. G.; Marti?nez, J. M. PACKMOL: A Package for Building Initial Configurations for Molecular Dynamics Simulations. J. Comput. Chem. 2009, 30, 2157? 2164, DOI: 10.1002/jcc.21224Google ScholarThere is no corresponding record for this reference.
- 41Shrestha, L. K.; Shrestha, R. G.; Aramaki, K. Intrinsic Parameters for the Structure Control of Nonionic Reverse Micelles in Styrene: SAXS and Rheometry Studies. Langmuir 2011, 27, 5862? 5873, DOI: 10.1021/la200663vGoogle Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXks1Gmu7g%253D&md5=e39403555c9ecf1bf569ed462721b55dIntrinsic Parameters for the Structure Control of Nonionic Reverse Micelles in Styrene: SAXS and Rheometry StudiesShrestha, Lok Kumar; Shrestha, Rekha Goswami; Aramaki, KenjiLangmuir (2011), 27 (10), 5862-5873CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concn., temp., and H2O addn. were studied using a small-angle x-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method was employed to deduce real-space structural information. The consistency of the GIFT method was tested by the geometrical model fittings, and the micellar aggregation no. (Nagg) was detd. Diglycerol monocaprate (C10G2), diglycerol monolaurate (C12G2), and diglycerol monomyristate (C14G2), spontaneously self-assemble into reverse micelles in org. solvent styrene under ambient conditions. The micellar size and the Nagg decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the crit. packing parameter (cpp). A clear picture of 1-dimensional (1-D) micellar growth was obsd. with an increase in surfactant wt. fraction (Ws) in the C10G2 system, which eventually formed rodlike micelles at Ws ≥ 15%. However, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with H2O, forming a H2O pool at the micellar core; the size of H2O-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that H2O addn. not only increase the micellar size but also increase the Nagg. Zero-shear viscosity decreases with surfactant chain but increase with Ws, supporting the results derived from SAXS.
- 42Shrestha, R. G.; Shrestha, L. K.; Ariga, K.; Abe, M. Reverse Micelle Microstructural Transformations Induced by Surfactant Molecular Structure, Concentration, and Temperature. J. Nanosci. Nanotechnol. 2011, 11, 7665? 7675, DOI: 10.1166/jnn.2011.5121Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlOkurbO&md5=49d78ed248b57792fcba0d056f516de6Reverse micelle microstructural transformations induced by surfactant molecular structure, concentration, and temperatureShrestha, Rekha Goswami; Shrestha, Lok Kumar; Ariga, Katsuhiko; Abe, MasahikoJournal of Nanoscience and Nanotechnology (2011), 11 (9), 7665-7675CODEN: JNNOAR; ISSN:1533-4880. (American Scientific Publishers)We have investigated the microstructural transformations of nonionic surfactant reverse micelles induced by surfactant mol. architecture, surfactant concn., and temp. in nonaq. media. The investigations were based on small-angle X-ray scattering (SAXS) and rheometry techniques. Polyglycerol polyoleic acid esters spontaneously self-assembled into reverse micelle in n-decane under ambient conditions, whose shape, size, and internal structure could be controlled by the surfactant mol. architecture, concn., and temp. The max. size of the micelles was found to increase with an increase in the hydrophilic headgroup size of the surfactant. On the other hand, an opposite trend was obsd. with an increase in the no. of oleate chain per surfactant mols., which was well supported by rheol. data; viscosity decreased with the no. of oleate chain per surfactant mol. The SAXS and rheol. data have shown a clear evidence of one dimensional micellar growth with increase in the surfactant concn. The relative viscosity, ηr, of the reverse micelle exhibited steeper concn. dependence behavior than those predicted for a dispersion of spherical particles based on the Krieger-Dougherty relation which provided a clear evidence of the presence of elongated micelles at higher concn. An ellipsoidal prolate-to-sphere type transition was obsd. upon heating.
- 43Kittipongpittaya, K.; Panya, A.; McClements, D. J.; Decker, E. A. Impact of Free Fatty Acids and Phospholipids on Reverse Micelles Formation and Lipid Oxidation in Bulk Oil. J. Am. Oil Chem. Soc. 2014, 91, 453? 462, DOI: 10.1007/s11746-013-2388-8Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVWksrnN&md5=505dd70f5401dcba77217e6329b697c1Impact of Free Fatty Acids and Phospholipids on Reverse Micelles Formation and Lipid Oxidation in Bulk OilKittipongpittaya, Ketinun; Panya, Atikorn; McClements, David Julian; Decker, Eric A.Journal of the American Oil Chemists' Society (2014), 91 (3), 453-462CODEN: JAOCA7; ISSN:0003-021X. (Springer)Assocn. colloids such as phospholipid reverse micelles could increase the rate of lipid oxidn. in bulk oils. In addn. to phospholipids, other surface active minor components in com. oils such as free fatty acids may impact lipid oxidn. rates and the phys. properties of reverse micelles. In this study, the effects of free fatty acids on changes in the crit. micelle concn. (CMC) of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) in stripped corn oil (SCO) were detd. by using the 7,7,8,8-tetracyanoquinodimethane solubilization technique. Different free fatty acids including myristoleic, oleic, elaidic, linoleic and eicosenoic were added at 0.5 % by wt along with the DOPC into the bulk oils. There was no significant effect of free fatty acids with different chain length, configuration and no. of double bonds on the CMC value for DOPC in bulk oil. However, increasing concns. of oleic acid (0.5 to 5 % by wt) caused the CMC value for DOPC in bulk oils to increase from 400 to 1,000 μmol/kg oil. Phys. properties of DOPC reverse micelles in the presence of free fatty acids in bulk oils were also investigated by the small angle X-ray scattering technique. Results showed that free fatty acids could impact on the reverse micelle structure of DOPC in bulk oils. Moreover, free fatty acid decreased pH inside reverse micelle as confirmed by the NMR studies. The oxidn. studies done by monitoring the lipid hydroperoxide and hexanal formation revealed that free fatty acids exhibited pro-oxidative activity in the presence and absence of DOPC. Different types of free fatty acids had similar pro-oxidative activity in bulk oil.
- 44Choe, E.; Min, D. B. Mechanisms and Factors for Edible Oil Oxidation. Compr. Rev. Food Sci. Food Saf. 2006, 5, 169? 186, DOI: 10.1111/j.1541-4337.2006.00009.xGoogle Scholar44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1ajsLvK&md5=2a052800b83bacdc6c1b79c03f158325Mechanisms and factors for edible oil oxidationChoe, Eunok; Min, David B.Comprehensive Reviews in Food Science and Food Safety (2006), 5 (4), 169-186CODEN: CRFSBJ; ISSN:1541-4337. (Institute of Food Technologists)A review. Edible oil is oxidized during processing and storage via autoxidn. and photosensitized oxidn., in which triplet oxygen (3O2) and singlet oxygen (1O2) react with the oil, resp. Autoxidn. of oils requires radical forms of acylglycerols, whereas photosensitized oxidn. does not require lipid radicals since 1O2 reacts directly with double bonds. Lipid hydroperoxides formed by 3O2 are conjugated dienes, whereas 1O2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decompd. to produce off-flavor compds. and the oil quality decreases. Autoxidn. of oil is accelerated by the presence of free fatty acids, mono- and diacylglycerols, metals such as iron, and thermally oxidized compds. Chlorophylls and phenolic compds. decrease the autoxidn. of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidn. chlorophyll acts as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidn. through 1O2 quenching. Temp., light, oxygen concn., oil processing, and fatty acid compn. also affect the oxidative stability of edible oil.
- 45Chen, B.; Han, A.; McClements, D. J.; Decker, E. A. Physical Structures in Soybean Oil and Their Impact on Lipid Oxidation. J. Agric. Food Chem. 2010, 58, 11993? 11999, DOI: 10.1021/jf102763pGoogle Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlalurvM&md5=695718df62c076236a5c29db31bef4a0Physical structures in soybean oil and their impact on lipid oxidationChen, Bingcan; Han, Ashley; McClements, David Julian; Decker, Eric AndrewJournal of Agricultural and Food Chemistry (2010), 58 (22), 11993-11999CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)The oxidn. of edible oil yields both primary and secondary oxidn. products (e.g., hydroperoxides, carbonyls, hydrocarbons, and epoxides), which produce undesirable sensory and biol. effects. Consequently, the suppression of lipid oxidn. in food matrixes is of great importance. The rate and extent of lipid oxidn. in many heterogeneous foods are strongly affected by the physicochem. characteristics of water-oil interfaces. This study examd. the ability of dioleoylphosphatidylcholine (DOPC) and water to form assocn. colloids within bulk oil, as well as their impact on lipid oxidn. kinetics. Attenuation was used to show the DOPC and water concns. at which assocn. colloids existed without altering the optical properties of the oil. Interfacial tension and fluorescence spectrometry showed the crit. micelle concn. (CMC) of DOPC in stripped soybean oil was around 650 μM at room temp. Small-angle X-ray scattering (SAXS) and fluorescence probes showed that water had a very strong impact on the properties of the assocn. colloids formed by DOPC. Measurement of primary and secondary lipid oxidn. products revealed that the assocn. colloids formed by DOPC had a pro-oxidant effect. The characterization of assocn. colloids could provide a better understanding of the mechanisms of lipid oxidn. in bulk oils and provide insights into new antioxidant technologies.
- 46Narang, A. S.; Delmarre, D.; Gao, D. Stable Drug Encapsulation in Micelles and Microemulsions. Int. J. Pharm. 2007, 345, 9? 25, DOI: 10.1016/j.ijpharm.2007.08.057Google Scholar46https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlWnt7vP&md5=3e6d32f298f88db872a0686c14de7a97Stable drug encapsulation in micelles and microemulsionsNarang, Ajit S.; Delmarre, David; Gao, DanchenInternational Journal of Pharmaceutics (2007), 345 (1-2), 9-25CODEN: IJPHDE; ISSN:0378-5173. (Elsevier Ltd.)A review. Oral absorption of hydrophobic drugs can be significantly improved using lipid-based non-particulate drug delivery systems, which avoid the dissoln. step. Micellar and microemulsion systems, being the most dispersed of all, appear the most promising. While these systems show high drug entrapment and release under sink conditions, the improvement in oral drug bioavailability is often unpredictable. The formulation and drug-related biopharmaceutical aspects of these systems that govern oral absorption have been widely studied. Among these, preventing drug pptn. upon aq. diln. could play a predominant role in many cases. Predictive ability and quick methods for assessment of such problems could be very useful to the formulators in selecting lead formulations. This review will attempt to summarize the research work that could be useful in developing these tools.
- 47Yara-Varo?n, E.; Li, Y.; Balcells, M.; Canela-Garayoa, R.; Fabiano-Tixier, A.-S.; Chemat, F. Vegetable Oils As Alternative Solvents for Green Oleo-extraction, Purification and Formulation of Food and Natural Products. Molecules 2017, 22, 1474, DOI: 10.3390/molecules22091474Google ScholarThere is no corresponding record for this reference.
- 48Cui, L.; Decker, E. A. Phospholipids in Foods: Prooxidants or Antioxidants?. J. Sci. Food Agric. 2016, 96, 18? 31, DOI: 10.1002/jsfa.7320Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1SqtL%252FE&md5=ffd67ec70bad50caae1d33aa36e4690fPhospholipids in foods: prooxidants or antioxidants?Cui, Leqi; Decker, Eric A.Journal of the Science of Food and Agriculture (2016), 96 (1), 18-31CODEN: JSFAAE; ISSN:0022-5142. (John Wiley & Sons Ltd.)A review. Lipid oxidn. is one of the major causes of quality deterioration in natural and processed foods and thus a large economic concern in the food industry. Phospholipids, esp. lecithins, are already widely used as natural emulsifiers and have been gaining increasing interest as natural antioxidants to control lipid oxidn. This review summarizes the fatty acid compn. and content of phospholipids naturally occurring in several foods. The role of phospholipids as substrates for lipid oxidn. is discussed, with a focus on meats and dairy products. Prooxidant and antioxidant mechanisms of phospholipids are also discussed to get a better understanding of the possible opportunities for using phospholipids as food antioxidants. © 2015 Society of Chem. Industry.
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References
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- 1Lombardo, D.; Kiselev, M. A.; Magazu?, S.; Calandra, P. Amphiphiles Self-Assembly: Basic Concepts and Future Perspectives of Supramolecular Approaches. Adv. Condens. Matter Phys. 2015, 2015, 151683, DOI: 10.1155/2015/151683There is no corresponding record for this reference.
- 2Pichot, R.; Watson, R. L.; Norton, I. T. Phospholipids at the Interface: Current Trends and Challenges. Int. J. Mol. Sci. 2013, 14, 11767? 11794, DOI: 10.3390/ijms1406117672https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtV2jtr7M&md5=1b6f7a5393f771383350ef189541d9a0Phospholipids at the interface : current trends and challengesPichot, Roman; Watson, Richard L.; Norton, Ian T.International Journal of Molecular Sciences (2013), 14 (6), 11767-11794, 28 pp.CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)A review. Phospholipids are one of the major structural elements of biol. membranes. Due to their amphiphilic character, they can adopt various mol. assemblies when dispersed in water, such as bilayer vesicles or micelles, which give them unique interfacial properties and render them very attractive in terms of foam or emulsion stabilization. This article aims at reviewing the properties of phospholipids at the air/water and oil/water interfaces, as well as the recent advances in using these natural components as stabilizers, alone or in combination with other compds. such as proteins. A discussion regarding the challenges and opportunities offered by phospholipids-stabilized structure concludes the review.
- 3Shchipunov, Y. A. Self-organising Structures of Lecithin. Russ. Chem. Rev. 1997, 66, 301? 322, DOI: 10.1070/RC1997v066n04ABEH000253There is no corresponding record for this reference.
- 4Ozturk, B.; McClements, D. J. Progress in Natural Emulsifiers for Utilization in Food Emulsions. Curr. Opin. Food Sci. 2016, 7, 1? 6, DOI: 10.1016/j.cofs.2015.07.008There is no corresponding record for this reference.
- 5Elnaggar, Y. S. R.; El-Refaie, W. M.; El-Massik, M. A.; Abdallah, O. Y. Lecithin-based Nanostructured Gels for Skin Delivery: An Update on State of Art and Recent Applications. J. Controlled Release 2014, 180, 10? 24, DOI: 10.1016/j.jconrel.2014.02.0045https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXkvVGqsr0%253D&md5=33e97dc01b64c158731d768f3e568e12Lecithin-based nanostructured gels for skin delivery: An update on state of art and recent applicationsElnaggar, Yosra S. R.; El-Refaie, Wessam M.; El-Massik, Magda A.; Abdallah, Ossama Y.Journal of Controlled Release (2014), 180 (), 10-24CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)A review. Conventional carriers for skin delivery encounter obstacles of drug leakage, scanty permeation and low entrapment efficiency. Phospholipid nanogels have recently been recognized as prominent delivery systems to circumvent such obstacles and impart easier application. The current review provides an overview on different types of lecithin nanostructured gels, with particular emphasis on liposomal vs. microemulsion gelled systems. Liposomal gels investigated encompassed classic liposomal hydrogel, modified liposomal gels (e.g. Transferosomal, Ethosomal, Pro-liposomal and Phytosomal gels), Microgel in liposomes (M-i-L) and Vesicular phospholipid gel (VPG). Microemulsion gelled systems encompassed Lecithin microemulsion-based organogels (LMBGs), Pluronic lecithin organogels (PLOs) and Lecithin-stabilized microemulsion-based hydrogels. All systems were reviewed regarding matrix compn., state of art, characterization and updated applications. Different classes of lecithin nanogels exhibited crucial impact on transdermal delivery regarding drug permeation, drug loading and stability aspects. Future perspectives of this theme issue are discussed based on current lab. studies.
- 6Fiordemondo, D.; Stano, P. Lecithin-Based Water-In-Oil Compartments as Dividing Bioreactors. ChemBioChem 2007, 8, 1965? 1973, DOI: 10.1002/cbic.2007001126https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlGhu7bK&md5=7a427b9bc0fda2131238f41141a3107aLecithin-based water-in-oil compartments as dividing bioreactorsFiordemondo, Deborah; Stano, PasqualeChemBioChem (2007), 8 (16), 1965-1973CODEN: CBCHFX; ISSN:1439-4227. (Wiley-VCH Verlag GmbH & Co. KGaA)Like liposomes, water-in-oil (w/o) emulsions have recently been used as bioreactors, since they permit facile compartmentation, and therefore the creation of a synthetic cell-like structure. We show here for the first time that lecithin-based w/o compartments can also be used for these purposes and in particular as compartments for hosting complex biochem. reactions that lead to protein synthesis. The expression of enhanced green fluorescent protein (EGFP), used as a model reaction, was followed by fluorescence microscopy. EGFP was synthesized inside the bioreactors either through simultaneous incorporation of all components for transcription and translation reactions in a single emulsion, or through the mixing of four different emulsions, each contg. only part of the mol. machinery. Mech. energy (i.e., stirring) must be provided to the system in order to force solute exchange and/or fusion processes between droplets. Finally, we demonstrate that, in the presence of excess lecithin, preformed w/o compartments can undergo spontaneous division, reducing the av. droplet size, increasing the no. of droplets, and continuing the protein expression after the division. We briefly comment on how this type of work extends and links the previously reported work on self-reprodn. in vesicles, micelles and reverse-micelles.
- 7Angelico, R.; Ceglie, A.; Olsson, U.; Palazzo, G. Phase Diagram and Phase Properties of the System Lecithin-Water-Cyclohexane. Langmuir 2000, 16, 2124? 2132, DOI: 10.1021/la99091907https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXmvVyqsA%253D%253D&md5=83a489af6f714d1965c4e2cd468086f2Phase Diagram and Phase Properties of the System Lecithin-Water-CyclohexaneAngelico, R.; Ceglie, A.; Olsson, U.; Palazzo, G.Langmuir (2000), 16 (5), 2124-2132CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The isothermal quasi-ternary phase diagram of the lecithin-cyclohexane-water system was constructed at 25 °C using a combination of polarizing microscopy, small-angle X-ray diffraction, and NMR techniques. The system contains four lyotropic liq.-cryst. phases and two isotropic liq. phases. Apart from the lamellar (Lα) phase, there are only reverse-type aggregates with a water interior, in addn. to an essentially pure water phase, whose relative locations in the phase diagram follow the sequence (from the oil corner to the surfactant corner): reverse micellar soln. (L2), reverse anisotropic nematic (N2), reverse micellar cubic (I2), reverse hexagonal (H2), and finally, the lamellar phase. The aggregates have a finite swelling with water, and coexistence with excess water is found at higher water contents. The area per lecithin mol. was detd. in the H2 and Lα phases. This area varies with the mole ratio [H2O]/[Lec] = W0 at lower W0 values, but sats. at an area of 90 Å2/mol. for W0 ⪆ 15. The phase diagram is discussed in relation to the known formation of giant wormlike reverse micelles in the liq. L2 phase. Of particular interest here is the transition from liq. (L2) to nematic (N2) as the wormlike aggregate concn. is increased.
- 8Lehtinen, O.-P.; Nugroho, R. W. N.; Lehtimaa, T.; Vierros, S.; Hiekkataipale, P.; Ruokolainen, J.; Sammalkorpi, M.; O?sterberg, M. Effect of Temperature, Water Content and Free Fatty Acid on Reverse Micelle Formation of Phospholipids in Vegetable Oil. Colloids Surf., B 2017, 160, 355? 363, DOI: 10.1016/j.colsurfb.2017.09.0508https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhsFKms7%252FK&md5=63cef9e605ab4626495221dd4a928f03Effect of temperature, water content and free fatty acid on reverse micelle formation of phospholipids in vegetable oilLehtinen, Olli-Pekka; Nugroho, Robertus Wahyu N.; Lehtimaa, Tuula; Vierros, Sampsa; Hiekkataipale, Panu; Ruokolainen, Janne; Sammalkorpi, Maria; Osterberg, MonikaColloids and Surfaces, B: Biointerfaces (2017), 160 (), 355-363CODEN: CSBBEQ; ISSN:0927-7765. (Elsevier B.V.)The self-assembly of phospholipids in oil, specifically lecithin in rapeseed oil, was investigated by combining exptl. and computational methods The influence of temp., water, and free fatty acids on the onset of lecithin aggregation in the rapeseed oil was detd. using the 7,7,8,8 -tetracyanoquinodimethane dye (TCNQ) solubilization method and the size and shape of the self-assembled lecithin structures were investigated by small-angle X-ray scattering and cryogenic transmission electron microscopy. In the absence of excess water in the system (0.03 wt-% water in oil), stable cylindrical lecithin reverse micelles were obsd. above the crit. micelle concn. (CMC). Comparing the aggregation response in room temp. and at 70 °C revealed that CMC decreased with increasing temp. Furthermore, already a modest amt. of added water (0.3 wt-% water in oil) was sufficient to induce the formation of lamellar lecithin structures, that phase sepd. from the oil. In low water content, oleic acid suppressed the formation of lecithin reverse micelles whereas in the presence of more water, the oleic acid stabilized the reverse micelles. Consequently, more water was needed to induce phase sepn. in the presence of oleic acid. Mol. dynamics simulations indicated that the stabilizing effect of oleic acid resulted from oleic acid enhancing phospholipid solubilization in the oil by forming a solvating shell around the phosphate head group. The findings showed that the response of the mixed surfactant system is a delicate interplay of the different components and variables. The significance of the observations is that multiple parameters need to be controlled for desired system response, for example towards vegetable oil purifn. or phospholipid based microemulsions.
- 9Lei, L.; Ma, Y.; Kodali, D. R.; Liang, J.; Davis, H. T. Ternary Phase Diagram of Soybean Phosphatidylcholine-Water-Soybean Oil and Its Application to the Water Degumming Process. J. Am. Oil Chem. Soc. 2003, 80, 383? 388, DOI: 10.1007/s11746-003-0708-y9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjslGmu74%253D&md5=1f19c6b2a7d4897aaa782a8e3d8942a0Ternary phase diagram of soybean phosphatidylcholine-water-soybean oil and its application to the water degumming processLei, Ling; Ma, Yue; Kodali, Dharma R.; Liang, Jingmei; Davis, H. TedJournal of the American Oil Chemists' Society (2003), 80 (4), 383-388CODEN: JAOCA7; ISSN:0003-021X. (AOCS Press)Crude soybean oil contains phospholipids (2.5 wt%) that must be removed from oil during processing. A common method is the water-degumming process. A ternary phase diagram of soybean oil-water-soybean PC, a major component of phospholipids, was established. From this diagram, phase transitions and compns. of phases can be detd. A theor. model describing the relationship between aggregation curvature and the amt. of water added is presented to explain the phase transitions. The amt. of water absorption by the lamellar phase should be larger than the crit. value of 34 wt% based on the total wt. of water and PC. Below this crit. amt., phospholipids tend to form liposomes. Above the crit. point and below the satn. point, larger aggregates of particles form and can be easily sepd. When more water is added to reach the water adsorption limit, about 40 wt% based on the total wt. of water and PC, a phase transition boundary is obsd., beyond which a third phase, water, appears and the particle size falls dramatically. In between the crit. line predicted by the model and the water adsorption satn. line obsd. exptl., there is an operation window on the ternary phase diagram for the water-degumming process.
- 10Njauw, C.-W.; Cheng, C.-Y.; Ivanov, V. A.; Khokhlov, A. R.; Tung, S.-H. Molecular Interactions between Lecithin and Bile Salts/Acids in Oils and Their Effects on Reverse Micellization. Langmuir 2013, 29, 3879? 3888, DOI: 10.1021/la304601p10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjtVCgu7g%253D&md5=a6f4a3f90f90894f0c84938c93d88142Molecular Interactions between Lecithin and Bile Salts/Acids in Oils and Their Effects on Reverse MicellizationNjauw, Ching-Wei; Cheng, Chih-Yang; Ivanov, Viktor A.; Khokhlov, Alexei R.; Tung, Shih-HuangLangmuir (2013), 29 (12), 3879-3888CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The addn. of bile salts to lecithin organosols induces the formation of reverse wormlike micelles and that the worms are similar to long polymer chains that entangle each other to form viscoelastic solns. The authors further studied the effects of different bile salts and bile acids on the growth of lecithin reverse worms in cyclohexane and n-decane. The authors used rheol. and small-angle scattering techniques to analyze the properties and structures of the reverse micelles. All of the bile salts can transform the originally spherical lecithin reverse micelles into wormlike micelles and their rheol. behaviors can be described by the single-relaxation-time Maxwell model. However, their efficiencies to induce the worms are different. In contrast, before phase sepn., bile acids can induce only short cylindrical micelles that are not long enough to impart viscoelasticity. FTIR spectroscopy was used to study the interactions between lecithin and bile salts/acids and found that different bile salts/acids employ different functional groups to form hydrogen bonds with lecithin. Such effects det. the relative positions of the bile salts/acids in the headgroups of lecithin, thus resulting in varying efficiencies to alter the effective crit. packing parameter for the formation of wormlike micelles. This work highlights the importance of intermol. interactions in mol. self-assembly.
- 11Schurtenberger, P.; Jerke, G.; Cavaco, C.; Pedersen, J. S. Cross-Section Structure of Cylindrical and Polymer-like Micelles from Small-Angle Scattering Data. 2. Experimental Results. Langmuir 1996, 12, 2433? 2440, DOI: 10.1021/la950744411https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XisFCnt74%253D&md5=98e550c49216e6bed73d7d21fc54bd69Cross-Section Structure of Cylindrical and Polymer-like Micelles from Small-Angle Scattering Data. 2. Experimental ResultsSchurtenberger, Peter; Jerke, Goetz; Cavaco, Carolina; Pedersen, Jan SkovLangmuir (1996), 12 (10), 2433-40CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)We report a small-angle neutron scattering (SANS) study of the cross-section structure of polymer-like lecithin reverse micelles in deuterated cyclohexane. We demonstrate that the application of the indirect Fourier transformation and square-root deconvolution methods to data from SANS measurements with cylindrical polymer-like micelles allows for a direct verification of the previously postulated geometrical model of flexible tubular structures with a well defined water core and a surfactant shell. By combining contrast variation expts. and data anal. performed on an abs. scale, we quant. deduce information on properties such as the extension of the aq. core and the degree of water penetration into the headgroup and solvent penetration into the tail region.
- 12Sugiura, S.; Ichikawa, S.; Sano, Y.; Nakajima, M.; Liu, X. Q.; Seki, M.; Furusaki, S. Formation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty Acids. J. Colloid Interface Sci. 2001, 240, 566? 572, DOI: 10.1006/jcis.2001.770312https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXlsFGqt7w%253D&md5=88be65bdd1180a9ee65f0aa5c561007cFormation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty AcidsSugiura, Shinji; Ichikawa, Sosaku; Sano, Yoh; Nakajima, Mitsutoshi; Liu, Xin Qi; Seki, Minoru; Furusaki, ShintaroJournal of Colloid and Interface Science (2001), 240 (2), 566-572CODEN: JCISA5; ISSN:0021-9797. (Academic Press)The formation of reversed micellar systems composed of phosphatidylcholine (PC) and fatty acid was newly demonstrated by a significant increase in H2O content in the org. Et oleate phase when the micelles were prepd. by the contact method. The solubilized H2O concn. in the reversed micellar org. phase reached 3%. The new systems are expected to be used as highly biocompatible reversed micellar systems. The structure of the reversed micelles composed of PC and oleic acid was characterized by detg. the H2O concn. and by small-angle x-ray scattering anal. The reversed micelles composed of PC and oleic acid formed in Et oleate were spherical. The radius of gyration was 30-50 Å. The size of the reversed micelles decreased with an increase in the oleic acid concn. and was independent of the PC concn. Exptl. results indicated that the structure of the reversed micellar system was detd. by the oleic acid concn. An increase in the PC concn. caused an increase in the no. of reversed micelles of the same size. These reversed micellar systems are expected to be used as solubilization media in pharmaceutical and food industries because they are not toxic. (c) 2001 Academic Press.
- 13Tung, S.-H.; Huang, Y.-E.; Raghavan, S. R. A New Reverse Wormlike Micellar System: Mixtures of Bile Salt and Lecithin in Organic Liquids. J. Am. Chem. Soc. 2006, 128, 5751? 5756, DOI: 10.1021/ja058376613https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xjt1yitbk%253D&md5=3bd2efb9a7bf2307d705009d5bf26d37A New Reverse Wormlike Micellar System: Mixtures of Bile Salt and Lecithin in Organic LiquidsTung, Shih-Huang; Huang, Yi-En; Raghavan, Srinivasa R.Journal of the American Chemical Society (2006), 128 (17), 5751-5756CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report a new route for forming reverse wormlike micelles (i.e., long, flexible micellar chains) in nonpolar org. liqs. such as cyclohexane and n-decane. This route involves the addn. of a bile salt (e.g., sodium deoxycholate) in trace amts. to solns. of the phospholipid lecithin. Previous recipes for reverse wormlike micelles have usually required the addn. of water to induce reverse micellar growth; here, we show that bile salts, due to their unique "facially amphiphilic" structure, can play a role analogous to that of water and promote the longitudinal aggregation of lecithin mols. into reverse micellar chains. The formation of transient entangled networks of these reverse micelles transforms low-viscosity lecithin organosols into strongly viscoelastic fluids. The zero-shear viscosity increases by more than 5 orders of magnitude, and it is the molar ratio of bile salt to lecithin that controls the viscosity enhancement. The growth of reverse wormlike micelles is also confirmed by small-angle neutron scattering (SANS) expts. on these fluids.
- 14Zhao, Y.; Zhang, J.; Wang, Q.; Li, W.; Li, J.; Han, B.; Wu, Z.; Zhang, K.; Li, Z. Cylindrical-to-Spherical Shape Transformation of Lecithin Reverse Micelles Induced by CO2. Langmuir 2010, 26, 4581? 4585, DOI: 10.1021/la904917n14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXivV2mur8%253D&md5=91fea3f110d05d178f6771db5c280cc8Cylindrical-to-Spherical Shape Transformation of Lecithin Reverse Micelles Induced by CO2Zhao, Yueju; Zhang, Jianling; Wang, Qian; Li, Wei; Li, Jianshen; Han, Buxing; Wu, Zhonghua; Zhang, Kunhao; Li, ZhihongLangmuir (2010), 26 (7), 4581-4585CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The effect of CO2 on the microstructure of L-α-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO2 could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform IR (FT-IR) and UV-vis techniques were also utilized to investigate intermol. interactions and micropolarity in the reverse micelles at different CO2 pressures. The redn. of the degree of hydrogen bonding between surfactant headgroups and water with added CO2 was found to be the main reason for the micellar shape transformation. In the absence of CO2, the hydrogen bonding between water and P[n.58875]O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO2 to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO2-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO2, and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO2. This method of tuning micellar shape has many advantages compared to traditional methods.
- 15Vierros, S.; Sammalkorpi, M. Phosphatidylcholine Reverse Micelles on the Wrong Track in Molecular Dynamics Simulations of Phospholipids in an Organic Solvent. J. Chem. Phys. 2015, 142, 094902, DOI: 10.1063/1.491402215https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXjvF2itLs%253D&md5=3f18514f9198ba8707a04fcc3adb5863Phosphatidylcholine reverse micelles on the wrong track in molecular dynamics simulations of phospholipids in an organic solventVierros, S.; Sammalkorpi, M.Journal of Chemical Physics (2015), 142 (9), 094902/1-094902/10CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)Here, we examine a well-characterized model system of phospholipids in cyclohexane via mol. dynamics simulations using a force field known for reproducing both phospholipid behavior in water and cyclohexane bulk properties to a high accuracy, CHARMM36, with the aim of evaluating the transferability of a force field parametrization from an aq. environment to an org. solvent. We compare the resulting reverse micelles with their expected exptl. shape and size, and find the model struggles with reproducing basic, exptl. known reverse micellar structural characteristics for common phosphadidylcholine lipids such as 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dioleyl-sn-glycero-3-phosphatidylcholine (DOPC), and 1,2-dilinoleyl-sn-glycero-3-phosphatidylcholine (DLPC) in cyclohexane solvent. We find evidence that the deviation from the exptl. behavior originates from an underestimation of the lipid tail-cyclohexane interaction in the model. We compensate for this, obtain reverse micellar structures within the exptl. expected range, and characterize these structurally in mol. detail. Our findings indicate extra caution and verification of model applicability is warranted in simulational studies employing std. biomol. models outside the usual aq. environment. (c) 2015 American Institute of Physics.
- 16Vierros, S.; Sammalkorpi, M. Role of Hydration in Phosphatidylcholine Reverse Micelle Structure and Gelation in Cyclohexane: A Molecular Dynamics Study. Phys. Chem. Chem. Phys. 2015, 17, 14951? 14960, DOI: 10.1039/C5CP01799H16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXotFClt7w%253D&md5=879e253bf0e6b0ca41860167d819952fRole of hydration in phosphatidylcholine reverse micelle structure and gelation in cyclohexane: a molecular dynamics studyVierros, S.; Sammalkorpi, M.Physical Chemistry Chemical Physics (2015), 17 (22), 14951-14960CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)In this work, we employ all-atom mol. dynamics simulations to examine the hydration response of phospholipid reverse micelles in cyclohexane. This ternary phospholipid-water-cyclohexane system is an important organogel forming system and the focus of this study is on gaining insight on the factors governing the gelation transition. We map the contributions rising from specific lipid-lipid and lipid-water interactions, and their response to increasing aggregate size and changes in water-to-lipid ratio. We find that, opposed to phospholipid-heptane organogels, in cyclohexane, lipid bridging and hydrogen bond driven stabilization of the lipid head group packing is at minor role in dictating the reverse micelle structural transitions corresponding to the organosol-organogel phase transition in this system. Instead, increasing the lipid head hydration changes the lipid packing factor directly which leads to gelation through the formation of long, wormlike micelles. Furthermore, the confined environment in the reverse micellar cores slows down the water dynamics significantly in comparison to fully hydrated phospholipid bilayers and at low water-to-lipid ratios this slow-down is even more significant. The findings map the role of hydration at microscopic level in these systems and could enable tailoring reverse micellar systems for applications relying on the structure and dynamics of the reverse micelles. Examples include such as drug transport, nanotemplating, or confined chem. in the reverse micelle core water space, e.g., in catalysis.
- 17Abel, S.; Galamba, N.; Karakas, E.; Marchi, M.; Thompson, W. H.; Laage, D. On the Structural and Dynamical Properties of DOPC Reverse Micelles. Langmuir 2016, 32, 10610? 10620, DOI: 10.1021/acs.langmuir.6b0256617https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFCms7vL&md5=b14c15e66eea9f096fe1f2d5503ea814On the Structural and Dynamical Properties of DOPC Reverse MicellesAbel, Stephane; Galamba, Nuno; Karakas, Esra; Marchi, Massimo; Thompson, Ward H.; Laage, DamienLangmuir (2016), 32 (41), 10610-10620CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)The structure and dynamics of phospholipid reverse micelles are studied by mol. dynamics. We report all-atom unconstrained simulations of 1,2-dioleoyl-sn-phosphatidylcholine (DOPC) reverse micelles in benzene of increasing sizes, with water-to-surfactant no. ratios ranging from W0 = 1 to 16. The aggregation no., i.e., the no. of DOPC mols. per reverse micelle, is detd. to fit exptl. light-scattering measurements of the reverse micelle diam. The simulated reverse micelles are found to be approx. spherical. Larger reverse micelles (W0 > 4) exhibit a layered structure with a water core and the hydration structure of DOPC phosphate head groups is similar to that found in phospholipid membranes. In contrast, the structure of smaller reverse micelles (W0 ≤ 4) cannot be described as a series of concentric layers successively contg. water, surfactant head groups, and surfactant tails, and the head groups are only partly hydrated and frequently present in the core. The dynamics of water mols. within the phospholipid reverse micelles slow down as the reverse micelle size decreases, in agreement with prior studies on AOT and Igepal reverse micelles. However, the av. water reorientation dynamics in DOPC reverse micelles is found to be much slower than in AOT and Igepal reverse micelles with the same W0 ratio. This is explained by the smaller water pool and by the stronger interactions between water and the charged head groups, as confirmed by the red-shift of the computed IR line shape with decreasing W0.
- 18Chatzidaki, M. D.; Papavasileiou, K. D.; Papadopoulos, M. G.; Xenakis, A. Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics Study. Langmuir 2017, 33, 5077? 5085, DOI: 10.1021/acs.langmuir.7b0021318https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXntlWisL4%253D&md5=6d6fd9ef8cf0ea417d1e5d42e7796a06Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics StudyChatzidaki, Maria D.; Papavasileiou, Konstantinos D.; Papadopoulos, Manthos G.; Xenakis, AristotelisLangmuir (2017), 33 (20), 5077-5085CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Water-in-oil microemulsions with biocompatible components were formulated to be used as carriers of natural antioxidants, such as hydroxytyrosol (HT) and gallic acid (GA). The system was composed of a mixt. of natural surfactants, lecithin and monoglycerides, medium chain triglycerides, and aq. phase. A dual approach was undertaken to study the structure and dynamics of these complicated systems. First, exptl. data were collected by using adequate techniques, such as dynamic light scattering (DLS) and ESR spectroscopy. Following this, a coarse-grained mol. dynamics (CGMD) study based on the exptl. compn. using the MARTINI force field was conducted. The simulations revealed the spontaneous formation of reverse micelles (RMs) starting from completely random initial conformations, underlying their enhanced thermodn. stability. The location of the bioactive mols., as well as the structure of the RM, were in accordance with the exptl. findings. Furthermore, GA mols. were found to be located inside the water core, in contrast to the HT ones, which seem to lie at the surfactant interfacial layer. The difference in the antioxidants' mol. location was only revealed in detail from the computational anal. and explains the RM's swelling obsd. by GA in DLS measurements.
- 19Vierros, S.; O?sterberg, M.; Sammalkorpi, M. Aggregation Response of Triglyceride Hydrolysis Products in Cyclohexane and Triolein. Phys. Chem. Chem. Phys. 2018, 20, 27192? 27204, DOI: 10.1039/C8CP05104F19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvV2ju7bJ&md5=1714eea3920c1d56b9fb5a3cac827d66Aggregation response of triglyceride hydrolysis products in cyclohexane and trioleinVierros, Sampsa; Osterberg, Monika; Sammalkorpi, MariaPhysical Chemistry Chemical Physics (2018), 20 (42), 27192-27204CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)Here, we examine the aggregation response of a series of triglyceride-based biosurfactants in cyclohexane and triglyceride solvents via all-atom mol. dynamics simulations and supporting expts. The surfactant aggregation follows in all systems, with only minor deviations, a multiple equil., i.e. open assocn., model. Monoglyceride aggregation in cyclohexane exhibits a crit. micellization concn., cmc, showing a cmc can exist even in a system following open assocn. However, the cmc is assocd. with a change in balance with oligomeric and larger aggregates in the soln., not an onset of aggregate formation. It is demonstrated that reverse micelles can form in the absence of water stabilized by intersurfactant hydrogen bonds alone, and that the polarity and hydrogen bonding capability of triolein systematically reduces surfactant aggregation in comparison to cyclohexane. A comparison between CHARMM27 and CHARMM36 simulation models reveals that while trends are preserved, the models differ in quant. prediction. Finally, consolidation of the general aggregation response trends predicted by the modeling are obtained via 7,7,8,8-tetracyanoquinodimethane dye (TCNQ) solubilization expts. on the corresponding model plant oil systems. The findings provide guidelines for predicting and controlling surfactant aggregation response in org. solvents via tuning the solvent polarity and hydrogen bonding ability, and a crit. assessment of simulation and aggregation models for surfactant systems in org. solvents.
- 20Issariyakul, T.; Dalai, A. K. Biodiesel from Vegetable Oils. Renewable Sustainable Energy Rev. 2014, 31, 446? 471, DOI: 10.1016/j.rser.2013.11.00120https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXivVCqur4%253D&md5=bb39a95aafd2efe00617a593f0698430Biodiesel from vegetable oilsIssariyakul, Titipong; Dalai, Ajay K.Renewable & Sustainable Energy Reviews (2014), 31 (), 446-471CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)A review. Biodiesel is gaining acceptance in the market as fuel and lubricant. It is expected that biodiesel industries will rapidly grow worldwide in the coming years and information on biodiesel feedstock, prodn., and characteristics will be crucial than ever esp. for those using vegetable oils as feedstock as these are currently the major sources for making biodiesel. In the present paper, a comprehensive review is reported on feedstock, prodn. technologies, and characteristics of biodiesel. More specifically, selected available vegetable oils are explored as feedstock for biodiesel prodn. Prodn. technologies including latest catalyst developments are discussed. Finally, biodiesel characteristics and parameters influencing the corresponding properties are revealed. Since this paper covers a wide range in biodiesel area, it serves as a general public education medium as well as a research ref. for biodiesel prodn. from vegetable oils.
- 21Xenakis, A.; Papadimitriou, V.; Sotiroudis, T. G. Colloidal Structures in Natural Oils. Curr. Opin. Colloid Interface Sci. 2010, 15, 55? 60, DOI: 10.1016/j.cocis.2009.11.00721https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhvFeku74%253D&md5=b6f1427b6ab0c0c54bef526d280eaa67Colloidal structures in natural oilsXenakis, Aristotelis; Papadimitriou, Vassiliki; Sotiroudis, Theodore G.Current Opinion in Colloid & Interface Science (2010), 15 (1-2), 55-60CODEN: COCSFL; ISSN:1359-0294. (Elsevier B.V.)A review. Natural oils are in general mixts. of triglycerides of various fatty acids contg. also small quantities of a multitude of other mols., the minor components. Their compn. depends on the type of their sources, either vegetable or animal, and on agronomic and climatic conditions. Extn. process highly influences the final compn. of the natural oils. The bulk triglyceride phase presents some structural order due to the internal polarity of these mols. The presence of the minor components, which are either amphiphilic or even hydrophilic together with some remaining moisture, induces colloidal assocn. within the lipophilic triglyceride phase. These local organizates host proteins and antioxidants that preserve their activity influencing the quality and stability of the edible oils. Of specific interest is the case of the veiled virgin olive oil, the untreated juice of the olives. Veiled virgin olive oil is unique among vegetable oils that is consumed without any refining process and consequently possesses colloidal structure. It is remarkable that this unfiltered oil presents higher resistance to oxidn. than the filtered ones, indicating the significance of internal structure to the final quality of the product.
- 22Boesecke, P. Reduction of Two-dimensional Small- and Wide-angle X-ray Scattering Data. J. Appl. Crystallogr. 2007, 40, s423? s427, DOI: 10.1107/S002188980700110022https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXkvVOhsr0%253D&md5=bf83c742c34db7a003bfc4569aadb3c5Reduction of two-dimensional small- and wide-angle x-ray scattering dataBoesecke, PeterJournal of Applied Crystallography (2007), 40 (S1), s423-s427CODEN: JACGAR; ISSN:0021-8898. (International Union of Crystallography)At the beamlines ID01 and ID02 of the European Synchrotron Radiation Facility in Grenoble, France, position-sensitive detectors for time-resolved small- and wide-angle x-ray scattering expts. are in use. The applied data redn. method has never been described comprehensively. This article outlines the parametrization of the raw data and introduces the programs developed for this purpose. Data redn. in the sense of this article means all steps between detector readout and normalization to abs. scattering intensities. This includes all corrections that can be made without any specific knowledge of the sample, e.g. detector dark-image correction, division by a flat-field and intensity normalization. Processed data are either two- or one-dimensional. Optionally, statistical errors can be propagated through the calcns.
- 23Orthaber, D.; Bergmann, A.; Glatter, O. SAXS Experiments on Absolute Scale with Kratky Systems Using Water As a Secondary Standard. J. Appl. Crystallogr. 2000, 33, 218? 225, DOI: 10.1107/S002188989901521623https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXivVaqurw%253D&md5=e36ee06d05cb163dac3647f2f71e127fSAXS experiments on absolute scale with Kratky systems using water as a secondary standardOrthaber, Doris; Bergmann, Alexander; Glatter, OttoJournal of Applied Crystallography (2000), 33 (2), 218-225CODEN: JACGAR; ISSN:0021-8898. (Munksgaard International Publishers Ltd.)For small-angle scattering, of x-rays (SAXS) and neutrons (SANS), the importance of abs. calibration was recognized since the inception of the technique. The work reported here focuses on SAXS measurements using Kratky slit systems. In former days, only mol. wts. or scattering per particle were detd., but today abs. calibration implies the use of the unit of cm-1 for the scattering curve. It is necessary to measure the so-called abs. intensity, which is the ratio of the scattering intensity to the primary intensity P0. Basically there are 2 possible ways to det. the abs. intensity. The 1st 1 is the direct method, which involves the mech. attenuation of the primary beam by a rotating disk or a moving slit. The 2nd is the indirect method, using secondary stds. H2O is well suited as a calibration std. because of the angle-independent scattering. The essential advantage is that the scattering of H2O only depends on the phys. property of isothermal compressibility. Before presenting an example of the practical performance of this method, the most important theor. equations for an SAS expt. on the abs. scale are summarized. With the slit collimation system, the scattering curve of H2O can be measured with high enough statistical accuracy. As a 1st example, the scattering curve of the protein lysozyme on the abs. scale is presented. The 2nd example is the detn. of the aggregation no. of a triblock copolymer P94 (EO17-PO42-EO17). Taking into account that at least 10% of the polymer sample consists of diblocks, the accuracy of ∼10% for the detd. aggregation no. is rather good. The data of P94 are considered on the particle scale to obtain the radial scattering-length d. distribution.
- 24Pedersen, J. S. Analysis of Small-Angle Scattering Data from Colloids and Polymer Solutions: Modeling and Least-squares Fitting. Adv. Colloid Interface Sci. 1997, 70, 171? 210, DOI: 10.1016/S0001-8686(97)00312-624https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXmvVSkt7Y%253D&md5=4422d69ed5b3845a00b2fc27fc3d8f8bAnalysis of small-angle scattering data from colloids and polymer solutions: modeling and least-squares fittingPedersen, Jan SkovAdvances in Colloid and Interface Science (1997), 70 (), 171-210CODEN: ACISB9; ISSN:0001-8686. (Elsevier)Anal. and modeling of small-angle scattering data from systems consisting of colloidal particles or polymers in soln. are discussed. A review with 95 refs.; the anal. requires application of least-squares methods; the basic principles of linear and nonlinear least-squares methods are summarized with emphasis on applications in anal. of small-angle scattering data. These include indirect Fourier transformation, square-root deconvolution, size distribution detns., and modeling. The inclusion of corrections for instrumental smearing effects is discussed. The most common anal. expressions for model form factors and structure factors are summarized. An example of anal. of small-angle neutron and x-ray scattering data for block copolymer micelles is given.
- 25Abraham, M. J.; Murtola, T.; Schulz, R.; Pa?ll, S.; Smith, J. C.; Hess, B.; Lindahl, E. GROMACS: High Performance Molecular Simulations through Multi-level Parallelism from Laptops to Supercomputers. SoftwareX 2015, 1?2, 19? 25, DOI: 10.1016/j.softx.2015.06.001There is no corresponding record for this reference.
- 26MacKerell, A. D. All-atom Empirical Potential for Molecular Modeling and Dynamics Studies of Proteins. J. Phys. Chem. B 1998, 102, 3586? 3616, DOI: 10.1021/jp973084f26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXivVOlsb4%253D&md5=ebb5100dafd0daeee60ca2fa66c1324aAll-Atom Empirical Potential for Molecular Modeling and Dynamics Studies of ProteinsMacKerell, A. D., Jr.; Bashford, D.; Bellott, M.; Dunbrack, R. L.; Evanseck, J. D.; Field, M. J.; Fischer, S.; Gao, J.; Guo, H.; Ha, S.; Joseph-McCarthy, D.; Kuchnir, L.; Kuczera, K.; Lau, F. T. K.; Mattos, C.; Michnick, S.; Ngo, T.; Nguyen, D. T.; Prodhom, B.; Reiher, W. E., III; Roux, B.; Schlenkrich, M.; Smith, J. C.; Stote, R.; Straub, J.; Watanabe, M.; Wiorkiewicz-Kuczera, J.; Yin, D.; Karplus, M.Journal of Physical Chemistry B (1998), 102 (18), 3586-3616CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)New protein parameters are reported for the all-atom empirical energy function in the CHARMM program. The parameter evaluation was based on a self-consistent approach designed to achieve a balance between the internal (bonding) and interaction (nonbonding) terms of the force field and among the solvent-solvent, solvent-solute, and solute-solute interactions. Optimization of the internal parameters used exptl. gas-phase geometries, vibrational spectra, and torsional energy surfaces supplemented with ab initio results. The peptide backbone bonding parameters were optimized with respect to data for N-methylacetamide and the alanine dipeptide. The interaction parameters, particularly the at. charges, were detd. by fitting ab initio interaction energies and geometries of complexes between water and model compds. that represented the backbone and the various side chains. In addn., dipole moments, exptl. heats and free energies of vaporization, solvation and sublimation, mol. vols., and crystal pressures and structures were used in the optimization. The resulting protein parameters were tested by applying them to noncyclic tripeptide crystals, cyclic peptide crystals, and the proteins crambin, bovine pancreatic trypsin inhibitor, and carbonmonoxy myoglobin in vacuo and in a crystal. A detailed anal. of the relationship between the alanine dipeptide potential energy surface and calcd. protein φ, χ angles was made and used in optimizing the peptide group torsional parameters. The results demonstrate that use of ab initio structural and energetic data by themselves are not sufficient to obtain an adequate backbone representation for peptides and proteins in soln. and in crystals. Extensive comparisons between mol. dynamics simulation and exptl. data for polypeptides and proteins were performed for both structural and dynamic properties. Calcd. data from energy minimization and dynamics simulations for crystals demonstrate that the latter are needed to obtain meaningful comparisons with exptl. crystal structures. The presented parameters, in combination with the previously published CHARMM all-atom parameters for nucleic acids and lipids, provide a consistent set for condensed-phase simulations of a wide variety of mols. of biol. interest.
- 27Scholfield, C. R.; Dutton, H. J.; Dimler, R. J. Carbohydrate Constituents of Soybean ?Lecithin. J. Am. Oil Chem. Soc. 1952, 29, 293? 298, DOI: 10.1007/BF0263147827https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG38Xlt1Srug%253D%253D&md5=88350a98fd1bc1e3b850ca3b5e8495e0Carbohydrate constituents of soybean "lecithin."Scholfield, C. R.; Dutton, Herbert J.; Dimler, Robert J.Journal of the American Oil Chemists' Society (1952), 29 (), 293-8CODEN: JAOCA7; ISSN:0003-021X.Both free and bound sugars in soybean lecithin were identified by means of paper chromatography along with an estimate of the amts. of each sugar in one sample. The free sugars were those remaining with the phosphatides after extn. with 50% alc. The free sugars consist mainly of sucrose and stachyose with a smaller amt. of raffinose. The greater part of the bound sugars are found with a phosphoinositide fraction which is more sol. in hexane; these sugars consist of galactose, mannose, and arabinose. Arabinose is freed by mild hydrolysis and all 3 by refluxing with 2 N H2SO4. The same 3 sugars, together with a smaller amt. of an unidentified sugar, are found in the corresponding fraction of corn phosphatides. In the abs. alc.-sol. fractions of both soybean and corn phosphatides the bound sugars consist of glucose and galactose.
- 28Feller, S. E.; MacKerell, A. D. An Improved Empirical Potential Energy Function for Molecular Simulations of Phospholipids. J. Phys. Chem. B 2000, 104, 7510? 7515, DOI: 10.1021/jp000784328https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXkvVWgtL4%253D&md5=cc7ce005f161c8a2bbe7ffd674754c8eAn Improved Empirical Potential Energy Function for Molecular Simulations of PhospholipidsFeller, Scott E.; MacKerell, Alexander D. ,Jr.Journal of Physical Chemistry B (2000), 104 (31), 7510-7515CODEN: JPCBFK; ISSN:1089-5647. (American Chemical Society)Improvements in the CHARMM all-atom force field for at.-level mol. simulations of lipids are reported. Substantial adjustments have been made to the Lennard-Jones (LJ) hydrocarbon and torsional parameters and to the partial at. charges and torsional parameters of the phosphate moiety. These changes were motivated by a combination of unexpected simulation results and recent high-level ab initio quantum mech. calcns. The parameter optimization procedure is described, and the resulting energy function validated by an 11 ns mol. dynamics simulation of a hydrated phospholipid bilayer. Of note is the influence of the hydrocarbon LJ parameters on the conformational properties of the aliph. tails, emphasizing the importance of obtaining the proper balance between the bonded and nonbonded portions of the force field. Compatibility with the CHARMM all-atom parameter sets for proteins and nucleic acids has been maintained such that high quality simulations of biol. interesting membranes are possible. The complete force field is included as Supporting Information and is available from www.pharmacy.umaryland.edu/∼alex.
- 29Bjelkmar, P.; Larsson, P.; Cuendet, M. A.; Hess, B.; Lindahl, E. Implementation of the CHARMM Force Field in GROMACS: Analysis of Protein Stability Effects from Correction Maps, Virtual Interaction Sites, and Water Models. J. Chem. Theory Comput. 2010, 6, 459? 466, DOI: 10.1021/ct900549r29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptlKhsw%253D%253D&md5=728be20d72ab18e98268c1a48efcdcb1Implementation of the CHARMM Force Field in GROMACS: Analysis of Protein Stability Effects from Correction Maps, Virtual Interaction Sites, and Water ModelsBjelkmar, Par; Larsson, Per; Cuendet, Michel A.; Hess, Berk; Lindahl, ErikJournal of Chemical Theory and Computation (2010), 6 (2), 459-466CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)CHARMM27 is a widespread and popular force field for biomol. simulation, and several recent algorithms such as implicit solvent models have been developed specifically for it. The authors have here implemented the CHARMM force field and all necessary extended functional forms in the GROMACS mol. simulation package, to make CHARMM-specific features available and to test them in combination with techniques for extended time steps, to make all major force fields available for comparison studies in GROMACS, and to test various solvent model optimizations, in particular the effect of Lennard-Jones interactions on hydrogens. The implementation has full support both for CHARMM-specific features such as multiple potentials over the same dihedral angle and the grid-based energy correction map on the .vphi., ψ protein backbone dihedrals, as well as all GROMACS features such as virtual hydrogen interaction sites that enable 5 fs time steps. The medium-to-long time effects of both the correction maps and virtual sites have been tested by performing a series of 100 ns simulations using different models for water representation, including comparisons between CHARMM and traditional TIP3P. Including the correction maps improves sampling of near native-state conformations in the authors' systems, and to some extent it is even able to refine distorted protein conformations. Finally, the authors show that this accuracy is largely maintained with a new implicit solvent implementation that works with virtual interaction sites, which enables performance in excess of 250 ns/day for a 900-atom protein on a quad-core desktop computer.
- 30He?nin, J.; Shinoda, W.; Klein, M. L. United-atom Acyl Chains for CHARMM Phospholipids. J. Phys. Chem. B 2008, 112, 7008? 7015, DOI: 10.1021/jp800687pThere is no corresponding record for this reference.
- 31Jo, S.; Song, K. C.; Desaire, H.; MacKerell, A. D., Jr.; Im, W. Glycan Reader: Automated Sugar Identification and Simulation Preparation for Carbohydrates and Glycoproteins. J. Comput. Chem. 2011, 32, 3135? 3141, DOI: 10.1002/jcc.2188631https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpvVamtrk%253D&md5=0cd04c0fb892d58ae69501f23ab079dfGlycan Reader: Automated sugar identification and simulation preparation for carbohydrates and glycoproteinsJo, Sunhwan; Song, Kevin C.; Desaire, Heather; MacKerell, Alexander D.; Im, WonpilJournal of Computational Chemistry (2011), 32 (14), 3135-3141CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)Understanding how glycosylation affects protein structure, dynamics, and function is an emerging and challenging problem in biol. As a first step toward glycan modeling in the context of structural glycobiol., the authors have developed Glycan Reader and integrated it into the CHARMM-GUI,. Glycan Reader greatly simplifies the reading of PDB structure files contg. glycans through (i) detection of carbohydrate mols., (ii) automatic annotation of carbohydrates based on their three-dimensional structures, (iii) recognition of glycosidic linkages between carbohydrates as well as N-/O-glycosidic linkages to proteins, and (iv) generation of inputs for the biomol. simulation program CHARMM with the proper glycosidic linkage setup. In addn., Glycan Reader is linked to other functional modules in CHARMM-GUI, allowing users to easily generate carbohydrate or glycoprotein mol. simulation systems in soln. or membrane environments and visualize the electrostatic potential on glycoprotein surfaces. These tools are useful for studying the impact of glycosylation on protein structure and dynamics. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011.
- 32Park, S.-J.; Lee, J.; Patel, D. S.; Ma, H.; Lee, H. S.; Jo, S.; Im, W. Glycan Reader Is Improved to Recognize Most Sugar Types and Chemical Modifications in the Protein Data Bank. Bioinformatics 2017, 33, 3051? 3057, DOI: 10.1093/bioinformatics/btx35832https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvFGju7bO&md5=16900496c68d5ffeedb08ed0e67e0b94Glycan Reader is improved to recognize most sugar types and chemical modifications in the Protein Data BankPark, Sang-Jun; Lee, Jumin; Patel, Dhilon S.; Ma, Hongjing; Lee, Hui Sun; Jo, Sunhwan; Im, WonpilBioinformatics (2017), 33 (19), 3051-3057CODEN: BOINFP; ISSN:1367-4811. (Oxford University Press)Motivation: Glycans play a central role in many essential biol. processes. Glycan Reader was originally developed to simplify the reading of Protein Data Bank (PDB) files contg. glycans through the automatic detection and annotation of sugars and glycosidic linkages between sugar units and to proteins, all based on at. coordinates and connectivity information. Carbohydrates can have various chem. modifications at different positions, making their chem. space much diverse. Unfortunately, current PDB files do not provide exact annotations for most carbohydrate derivs. and more than 50% of PDB glycan chains have at least one carbohydrate deriv. that could not be correctly recognized by the original Glycan Reader. Results: Glycan Reader has been improved and now identifies most sugar types and chem. modifications (including various glycolipids) in the PDB, and both PDB and PDBx/mmCIF formats are supported. CHARMM-GUI Glycan Reader is updated to generate the simulation system and input of various glycoconjugates with most sugar types and chem. modifications. It also offers a new functionality to edit the glycan structures through addn./deletion/modification of glycosylation types, sugar types, chem. modifications, glycosidic linkages, and anomeric states. The simulation system and input files can be used for CHARMM, NAMD, GROMACS, AMBER, GENESIS, LAMMPS, Desmond, OpenMM, and CHARMM/OpenMM. Glycan Fragment Database in GlycanStructure.Org is also updated to provide an intuitive glycan sequence search tool for complex glycan structures with various chem. modifications in the PDB.
- 33Jo, S.; Kim, T.; Iyer, V. G.; Im, W. CHARMM-GUI: A Web-based Graphical User Interface for CHARMM. J. Comput. Chem. 2008, 29, 1859? 1865, DOI: 10.1002/jcc.2094533https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXosVKksbc%253D&md5=112a3dd61d792b040f9f716b32220d7eCHARMM-GUI: a web-based graphical user interface for CHARMMJo, Sunhwan; Kim, Taehoon; Iyer, Vidyashankara G.; Im, WonpilJournal of Computational Chemistry (2008), 29 (11), 1859-1865CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)CHARMM is an academic research program used widely for macromol. mechanics and dynamics with versatile anal. and manipulation tools of at. coordinates and dynamics trajectories. CHARMM-GUI, http://www.charmm-gui.org, has been developed to provide a web-based graphical user interface to generate various input files and mol. systems to facilitate and standardize the usage of common and advanced simulation techniques in CHARMM. The web environment provides an ideal platform to build and validate a mol. model system in an interactive fashion such that, if a problem is found through visual inspection, one can go back to the previous setup and regenerate the whole system again. In this article, we describe the currently available functional modules of CHARMM-GUI Input Generator that form a basis for the advanced simulation techniques. Future directions of the CHARMM-GUI development project are also discussed briefly together with other features in the CHARMM-GUI website, such as Archive and Movie Gallery.
- 34Brooks, B. R. CHARMM: The Biomolecular Simulation Program. J. Comput. Chem. 2009, 30, 1545? 1614, DOI: 10.1002/jcc.2128734https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXms1Ciu70%253D&md5=2c6a2be869362d7131f5aea8411c1552CHARMM: The biomolecular simulation programBrooks, B. R.; Brooks, C. L., III; Mackerell, A. D., Jr.; Nilsson, L.; Petrella, R. J.; Roux, B.; Won, Y.; Archontis, G.; Bartels, C.; Boresch, S.; Caflisch, A.; Caves, L.; Cui, Q.; Dinner, A. R.; Feig, M.; Fischer, S.; Gao, J.; Hodoscek, M.; Im, W.; Kuczera, K.; Lazaridis, T.; Ma, J.; Ovchinnikov, V.; Paci, E.; Pastor, R. W.; Post, C. B.; Pu, J. Z.; Schaefer, M.; Tidor, B.; Venable, R. M.; Woodcock, H. L.; Wu, X.; Yang, W.; York, D. M.; Karplus, M.Journal of Computational Chemistry (2009), 30 (10), 1545-1614CODEN: JCCHDD; ISSN:0192-8651. (John Wiley & Sons, Inc.)A review. CHARMM (Chem. at HARvard Mol. Mechanics) is a highly versatile and widely used mol. simulation program. It has been developed over the last three decades with a primary focus on mols. of biol. interest, including proteins, peptides, lipids, nucleic acids, carbohydrates, and small mol. ligands, as they occur in soln., crystals, and membrane environments. For the study of such systems, the program provides a large suite of computational tools that include numerous conformational and path sampling methods, free energy estimators, mol. minimization, dynamics, and anal. techniques, and model-building capabilities. The CHARMM program is applicable to problems involving a much broader class of many-particle systems. Calcns. with CHARMM can be performed using a no. of different energy functions and models, from mixed quantum mech.-mol. mech. force fields, to all-atom classical potential energy functions with explicit solvent and various boundary conditions, to implicit solvent and membrane models. The program has been ported to numerous platforms in both serial and parallel architectures. This article provides an overview of the program as it exists today with an emphasis on developments since the publication of the original CHARMM article in 1983. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009.
- 35Bussi, G.; Donadio, D.; Parrinello, M. Canonical Sampling through Velocity Rescaling. J. Chem. Phys. 2007, 126, 014101, DOI: 10.1063/1.240842035https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXosVCltg%253D%253D&md5=9c182b57bfc65bca6be23c8c76b4be77Canonical sampling through velocity rescalingBussi, Giovanni; Donadio, Davide; Parrinello, MicheleJournal of Chemical Physics (2007), 126 (1), 014101/1-014101/7CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)The authors present a new mol. dynamics algorithm for sampling the canonical distribution. In this approach the velocities of all the particles are rescaled by a properly chosen random factor. The algorithm is formally justified and it is shown that, in spite of its stochastic nature, a quantity can still be defined that remains const. during the evolution. In numerical applications this quantity can be used to measure the accuracy of the sampling. The authors illustrate the properties of this new method on Lennard-Jones and TIP4P water models in the solid and liq. phases. Its performance is excellent and largely independent of the thermostat parameter also with regard to the dynamic properties.
- 36Parrinello, M.; Rahman, A. Polymorphic Transitions in Single Crystals: A New Molecular Dynamics Method. J. Appl. Phys. 1981, 52, 7182? 7190, DOI: 10.1063/1.32869336https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38XislSnuw%253D%253D&md5=a0a5617389f6cabbf2a405c649aadf03Polymorphic transitions in single crystals: A new molecular dynamics methodParrinello, M.; Rahman, A.Journal of Applied Physics (1981), 52 (12), 7182-90CODEN: JAPIAU; ISSN:0021-8979.A Lagrangian formulation is introduced; it can be used to make mol. dynamics (MD) calcns. on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamic equations given by this Lagrangian. This MD technique was used to the study of structural transitions of a Ni single crystal under uniform uniaxial compressive and tensile loads. Some results regarding the stress-strain relation obtained by static calcns. are invalid at finite temp. Under compressive loading, the model of Ni shows a bifurcation in its stress-strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. Such a transition could perhaps be obsd. exptl. under extreme conditions of shock.
- 37Essmann, U.; Perera, L.; Berkowitz, M. L.; Darden, T.; Lee, H.; Pedersen, L. G. A Smooth Particle Mesh Ewald Method. J. Chem. Phys. 1995, 103, 8577? 8593, DOI: 10.1063/1.47011737https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXptlehtrw%253D&md5=092a679dd3bee08da28df41e302383a7A smooth particle mesh Ewald methodEssmann, Ulrich; Perera, Lalith; Berkowitz, Max L.; Darden, Tom; Lee, Hsing; Pedersen, Lee G.Journal of Chemical Physics (1995), 103 (19), 8577-93CODEN: JCPSA6; ISSN:0021-9606. (American Institute of Physics)The previously developed particle mesh Ewald method is reformulated in terms of efficient B-spline interpolation of the structure factors. This reformulation allows a natural extension of the method to potentials of the form 1/rp with p ≥ 1. Furthermore, efficient calcn. of the virial tensor follows. Use of B-splines in the place of Lagrange interpolation leads to analytic gradients as well as a significant improvement in the accuracy. The authors demonstrate that arbitrary accuracy can be achieved, independent of system size N, at a cost that scales as N log(N). For biomol. systems with many thousands of atoms and this method permits the use of Ewald summation at a computational cost comparable to that of a simple truncation method of 10 Å or less.
- 38Hess, B.; Bekker, H.; Berendsen, H. J. C.; Fraaije, J. G. E. M. LINCS: A Linear Constraint Solver for Molecular Simulations. J. Comput. Chem. 1997, 18, 1463? 1472, DOI: 10.1002/(SICI)1096-987X(199709)18:12<1463::AID-JCC4>3.0.CO;2-H38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXlvV2nu7g%253D&md5=890f8af0d2ca1f65aa93db5a3a0bacf2LINCS: a linear constraint solver for molecular simulationsHess, Berk; Bekker, Henk; Berendsen, Herman J. C.; Fraaije, Johannes G. E. M.Journal of Computational Chemistry (1997), 18 (12), 1463-1472CODEN: JCCHDD; ISSN:0192-8651. (Wiley)We present a new LINear Constraint Solver (LINCS) for mol. simulations with bond constraints using the enzyme lysozyme and a 32-residue peptide as test systems. The algorithm is inherently stable, as the constraints themselves are reset instead of derivs. of the constraints, thereby eliminating drift. Although the derivation of the algorithm is presented in terms of matrixes, no matrix matrix multiplications are needed and only the nonzero matrix elements have to be stored, making the method useful for very large mols. At the same accuracy, the LINCS algorithm is 3-4 times faster than the SHAKE algorithm. Parallelization of the algorithm is straightforward.
- 39Miyamoto, S.; Kollman, P. A. Settle: An Analytical Version of the SHAKE and RATTLE Algorithm for Rigid Water Models. J. Comput. Chem. 1992, 13, 952? 962, DOI: 10.1002/jcc.54013080539https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38Xlslykt7o%253D&md5=65da9d55c7905abeaf7708d91a09e6e4SETTLE: an analytical version of the SHAKE and RATTLE algorithm for rigid water modelsMiyamoto, Shuichi; Kollman, Peter A.Journal of Computational Chemistry (1992), 13 (8), 952-62CODEN: JCCHDD; ISSN:0192-8651.An anal. algorithm, called SETTLE, for resetting the positions and velocities to satisfy the holonomic constraints on the rigid water model is presented. This method is based on the Cartesian coordinate system and can be used in place of SHAKE and RATTLE. The authors implemented this algorithm in the SPASMS package of mol. mechanics and dynamics. Several series of mol. dynamics simulations were carried out to examine the performance of the new algorithm in comparison with the original RATTLE method. SETTLE is of higher accuracy and is faster than RATTLE with reasonable tolerances by three to nine times on a scalar machine. The performance improvement ranged from factors of 26 to 98 on a vector machine since the method presented is not iterative.
- 40Marti?nez, L.; Andrade, R.; Birgin, E. G.; Marti?nez, J. M. PACKMOL: A Package for Building Initial Configurations for Molecular Dynamics Simulations. J. Comput. Chem. 2009, 30, 2157? 2164, DOI: 10.1002/jcc.21224There is no corresponding record for this reference.
- 41Shrestha, L. K.; Shrestha, R. G.; Aramaki, K. Intrinsic Parameters for the Structure Control of Nonionic Reverse Micelles in Styrene: SAXS and Rheometry Studies. Langmuir 2011, 27, 5862? 5873, DOI: 10.1021/la200663v41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXks1Gmu7g%253D&md5=e39403555c9ecf1bf569ed462721b55dIntrinsic Parameters for the Structure Control of Nonionic Reverse Micelles in Styrene: SAXS and Rheometry StudiesShrestha, Lok Kumar; Shrestha, Rekha Goswami; Aramaki, KenjiLangmuir (2011), 27 (10), 5862-5873CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concn., temp., and H2O addn. were studied using a small-angle x-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method was employed to deduce real-space structural information. The consistency of the GIFT method was tested by the geometrical model fittings, and the micellar aggregation no. (Nagg) was detd. Diglycerol monocaprate (C10G2), diglycerol monolaurate (C12G2), and diglycerol monomyristate (C14G2), spontaneously self-assemble into reverse micelles in org. solvent styrene under ambient conditions. The micellar size and the Nagg decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the crit. packing parameter (cpp). A clear picture of 1-dimensional (1-D) micellar growth was obsd. with an increase in surfactant wt. fraction (Ws) in the C10G2 system, which eventually formed rodlike micelles at Ws ≥ 15%. However, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with H2O, forming a H2O pool at the micellar core; the size of H2O-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that H2O addn. not only increase the micellar size but also increase the Nagg. Zero-shear viscosity decreases with surfactant chain but increase with Ws, supporting the results derived from SAXS.
- 42Shrestha, R. G.; Shrestha, L. K.; Ariga, K.; Abe, M. Reverse Micelle Microstructural Transformations Induced by Surfactant Molecular Structure, Concentration, and Temperature. J. Nanosci. Nanotechnol. 2011, 11, 7665? 7675, DOI: 10.1166/jnn.2011.512142https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtlOkurbO&md5=49d78ed248b57792fcba0d056f516de6Reverse micelle microstructural transformations induced by surfactant molecular structure, concentration, and temperatureShrestha, Rekha Goswami; Shrestha, Lok Kumar; Ariga, Katsuhiko; Abe, MasahikoJournal of Nanoscience and Nanotechnology (2011), 11 (9), 7665-7675CODEN: JNNOAR; ISSN:1533-4880. (American Scientific Publishers)We have investigated the microstructural transformations of nonionic surfactant reverse micelles induced by surfactant mol. architecture, surfactant concn., and temp. in nonaq. media. The investigations were based on small-angle X-ray scattering (SAXS) and rheometry techniques. Polyglycerol polyoleic acid esters spontaneously self-assembled into reverse micelle in n-decane under ambient conditions, whose shape, size, and internal structure could be controlled by the surfactant mol. architecture, concn., and temp. The max. size of the micelles was found to increase with an increase in the hydrophilic headgroup size of the surfactant. On the other hand, an opposite trend was obsd. with an increase in the no. of oleate chain per surfactant mols., which was well supported by rheol. data; viscosity decreased with the no. of oleate chain per surfactant mol. The SAXS and rheol. data have shown a clear evidence of one dimensional micellar growth with increase in the surfactant concn. The relative viscosity, ηr, of the reverse micelle exhibited steeper concn. dependence behavior than those predicted for a dispersion of spherical particles based on the Krieger-Dougherty relation which provided a clear evidence of the presence of elongated micelles at higher concn. An ellipsoidal prolate-to-sphere type transition was obsd. upon heating.
- 43Kittipongpittaya, K.; Panya, A.; McClements, D. J.; Decker, E. A. Impact of Free Fatty Acids and Phospholipids on Reverse Micelles Formation and Lipid Oxidation in Bulk Oil. J. Am. Oil Chem. Soc. 2014, 91, 453? 462, DOI: 10.1007/s11746-013-2388-843https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvVWksrnN&md5=505dd70f5401dcba77217e6329b697c1Impact of Free Fatty Acids and Phospholipids on Reverse Micelles Formation and Lipid Oxidation in Bulk OilKittipongpittaya, Ketinun; Panya, Atikorn; McClements, David Julian; Decker, Eric A.Journal of the American Oil Chemists' Society (2014), 91 (3), 453-462CODEN: JAOCA7; ISSN:0003-021X. (Springer)Assocn. colloids such as phospholipid reverse micelles could increase the rate of lipid oxidn. in bulk oils. In addn. to phospholipids, other surface active minor components in com. oils such as free fatty acids may impact lipid oxidn. rates and the phys. properties of reverse micelles. In this study, the effects of free fatty acids on changes in the crit. micelle concn. (CMC) of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) in stripped corn oil (SCO) were detd. by using the 7,7,8,8-tetracyanoquinodimethane solubilization technique. Different free fatty acids including myristoleic, oleic, elaidic, linoleic and eicosenoic were added at 0.5 % by wt along with the DOPC into the bulk oils. There was no significant effect of free fatty acids with different chain length, configuration and no. of double bonds on the CMC value for DOPC in bulk oil. However, increasing concns. of oleic acid (0.5 to 5 % by wt) caused the CMC value for DOPC in bulk oils to increase from 400 to 1,000 μmol/kg oil. Phys. properties of DOPC reverse micelles in the presence of free fatty acids in bulk oils were also investigated by the small angle X-ray scattering technique. Results showed that free fatty acids could impact on the reverse micelle structure of DOPC in bulk oils. Moreover, free fatty acid decreased pH inside reverse micelle as confirmed by the NMR studies. The oxidn. studies done by monitoring the lipid hydroperoxide and hexanal formation revealed that free fatty acids exhibited pro-oxidative activity in the presence and absence of DOPC. Different types of free fatty acids had similar pro-oxidative activity in bulk oil.
- 44Choe, E.; Min, D. B. Mechanisms and Factors for Edible Oil Oxidation. Compr. Rev. Food Sci. Food Saf. 2006, 5, 169? 186, DOI: 10.1111/j.1541-4337.2006.00009.x44https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1ajsLvK&md5=2a052800b83bacdc6c1b79c03f158325Mechanisms and factors for edible oil oxidationChoe, Eunok; Min, David B.Comprehensive Reviews in Food Science and Food Safety (2006), 5 (4), 169-186CODEN: CRFSBJ; ISSN:1541-4337. (Institute of Food Technologists)A review. Edible oil is oxidized during processing and storage via autoxidn. and photosensitized oxidn., in which triplet oxygen (3O2) and singlet oxygen (1O2) react with the oil, resp. Autoxidn. of oils requires radical forms of acylglycerols, whereas photosensitized oxidn. does not require lipid radicals since 1O2 reacts directly with double bonds. Lipid hydroperoxides formed by 3O2 are conjugated dienes, whereas 1O2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decompd. to produce off-flavor compds. and the oil quality decreases. Autoxidn. of oil is accelerated by the presence of free fatty acids, mono- and diacylglycerols, metals such as iron, and thermally oxidized compds. Chlorophylls and phenolic compds. decrease the autoxidn. of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidn. chlorophyll acts as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidn. through 1O2 quenching. Temp., light, oxygen concn., oil processing, and fatty acid compn. also affect the oxidative stability of edible oil.
- 45Chen, B.; Han, A.; McClements, D. J.; Decker, E. A. Physical Structures in Soybean Oil and Their Impact on Lipid Oxidation. J. Agric. Food Chem. 2010, 58, 11993? 11999, DOI: 10.1021/jf102763p45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXhtlalurvM&md5=695718df62c076236a5c29db31bef4a0Physical structures in soybean oil and their impact on lipid oxidationChen, Bingcan; Han, Ashley; McClements, David Julian; Decker, Eric AndrewJournal of Agricultural and Food Chemistry (2010), 58 (22), 11993-11999CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)The oxidn. of edible oil yields both primary and secondary oxidn. products (e.g., hydroperoxides, carbonyls, hydrocarbons, and epoxides), which produce undesirable sensory and biol. effects. Consequently, the suppression of lipid oxidn. in food matrixes is of great importance. The rate and extent of lipid oxidn. in many heterogeneous foods are strongly affected by the physicochem. characteristics of water-oil interfaces. This study examd. the ability of dioleoylphosphatidylcholine (DOPC) and water to form assocn. colloids within bulk oil, as well as their impact on lipid oxidn. kinetics. Attenuation was used to show the DOPC and water concns. at which assocn. colloids existed without altering the optical properties of the oil. Interfacial tension and fluorescence spectrometry showed the crit. micelle concn. (CMC) of DOPC in stripped soybean oil was around 650 μM at room temp. Small-angle X-ray scattering (SAXS) and fluorescence probes showed that water had a very strong impact on the properties of the assocn. colloids formed by DOPC. Measurement of primary and secondary lipid oxidn. products revealed that the assocn. colloids formed by DOPC had a pro-oxidant effect. The characterization of assocn. colloids could provide a better understanding of the mechanisms of lipid oxidn. in bulk oils and provide insights into new antioxidant technologies.
- 46Narang, A. S.; Delmarre, D.; Gao, D. Stable Drug Encapsulation in Micelles and Microemulsions. Int. J. Pharm. 2007, 345, 9? 25, DOI: 10.1016/j.ijpharm.2007.08.05746https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtlWnt7vP&md5=3e6d32f298f88db872a0686c14de7a97Stable drug encapsulation in micelles and microemulsionsNarang, Ajit S.; Delmarre, David; Gao, DanchenInternational Journal of Pharmaceutics (2007), 345 (1-2), 9-25CODEN: IJPHDE; ISSN:0378-5173. (Elsevier Ltd.)A review. Oral absorption of hydrophobic drugs can be significantly improved using lipid-based non-particulate drug delivery systems, which avoid the dissoln. step. Micellar and microemulsion systems, being the most dispersed of all, appear the most promising. While these systems show high drug entrapment and release under sink conditions, the improvement in oral drug bioavailability is often unpredictable. The formulation and drug-related biopharmaceutical aspects of these systems that govern oral absorption have been widely studied. Among these, preventing drug pptn. upon aq. diln. could play a predominant role in many cases. Predictive ability and quick methods for assessment of such problems could be very useful to the formulators in selecting lead formulations. This review will attempt to summarize the research work that could be useful in developing these tools.
- 47Yara-Varo?n, E.; Li, Y.; Balcells, M.; Canela-Garayoa, R.; Fabiano-Tixier, A.-S.; Chemat, F. Vegetable Oils As Alternative Solvents for Green Oleo-extraction, Purification and Formulation of Food and Natural Products. Molecules 2017, 22, 1474, DOI: 10.3390/molecules22091474There is no corresponding record for this reference.
- 48Cui, L.; Decker, E. A. Phospholipids in Foods: Prooxidants or Antioxidants?. J. Sci. Food Agric. 2016, 96, 18? 31, DOI: 10.1002/jsfa.732048https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXht1SqtL%252FE&md5=ffd67ec70bad50caae1d33aa36e4690fPhospholipids in foods: prooxidants or antioxidants?Cui, Leqi; Decker, Eric A.Journal of the Science of Food and Agriculture (2016), 96 (1), 18-31CODEN: JSFAAE; ISSN:0022-5142. (John Wiley & Sons Ltd.)A review. Lipid oxidn. is one of the major causes of quality deterioration in natural and processed foods and thus a large economic concern in the food industry. Phospholipids, esp. lecithins, are already widely used as natural emulsifiers and have been gaining increasing interest as natural antioxidants to control lipid oxidn. This review summarizes the fatty acid compn. and content of phospholipids naturally occurring in several foods. The role of phospholipids as substrates for lipid oxidn. is discussed, with a focus on meats and dairy products. Prooxidant and antioxidant mechanisms of phospholipids are also discussed to get a better understanding of the possible opportunities for using phospholipids as food antioxidants. © 2015 Society of Chem. Industry.