Nature 331, 457 - 460 (04 February 1988); doi:10.1038/331457a0

Multiple liquid crystal phases of DNA at high concentrations

Teresa E. Strzelecka, Michael W. Davidson & Randolph L. Rill

Department of Chemistry and Institute of Molecular Biophysics, The Florida State University, Tallahassee, Florida 32306-3006, USA

DNA packaging in vivo is very tight, with volume concentrations approaching 70% w/v in sperm heads, virus capsids and bacterial nucleoids^1–3. The packaging mechanisms adopted may be related to the natural tendency of semi-rigid polymers to form liquid crystalline phases in concentrated solutions^4–8. We find that DNA forms at least three distinct liquid crystalline phases at concentrations comparable to those in vivo, with phase transitions occurring over relatively narrow ranges of DNA concentration. A weakly birefringent, dynamic, 'precholesteric' mesophase with microscopic textures intermediate between those of a nematic and a true cholesteric phase forms at the lowest concentrations required for phase separation. At slightly higher DNA concentrations, a second mesophase forms which is a strongly birefringent, well-ordered cholesteric phase with a concentration-dependent pitch varying from 2 to lOm. At the highest DNA concentrations, a phase forms which is two-dimensionally ordered and resembles smectic phases of thermotropic liquid crystals observed with small molecules.

References

1.	Du Praw, E. J. DNA and Chromosomes (Holt, Rinehart & Winston, New York, 1970).
2.	Earnshaw, W. C. & Casjens, S. R. Cell 21, 319−331 (1980). | Article | PubMed | ISI | ChemPort |
3.	Sipski, W. & Wagner, T. E. Biopolymers 16, 573−582 (1977). | Article | PubMed |
4.	Onsager, L. Ann. N.Y. Acad. Sci. 51, 627−659 (1949). | ChemPort |
5.	Flory, P. J. Proc. R. Soc. A234, 60−89 (1956). | ChemPort |
6.	Flory, P. J. in Polymer Liquid Crystals (eds. Ciferri, A., Krigbaum, W. R. & Meyer, R. B.) 103−112 (Academic, New York, 1982). | ChemPort |
7.	Robinson, C. Trans. Faraday Soc. 52, 571−592 (1956). | Article | ChemPort |
8.	Miller, W. A. Rev. phys. Chem. 29, 519−535 (1979).
9.	Manning, G. S. Q. Rev. Biophys. 11, 170−246 (1978).
10.	Stigter, D. Biopolymers 16, 1435−1448 (1977). | Article | PubMed | ChemPort |
11.	Stigter, D. J. phys. Chem. 82, 1603−1606 (1978). | Article | ChemPort |
12.	Brian, A. A., Frisch, H. L. & Lerman, L. S. Biopolymers 20, 1305−1328 (1981). | Article | PubMed | ChemPort |
13.	LeBret, M. & Zimm, B. H. Biopolymers 23, 271−285 & 286−312 (1984).
14.	Rill, R. L., Hilliard, P. R. & Levy, G. C. J. biol. Chem. 258, 250−256 (1983). | PubMed | ChemPort |
15.	Rill, R. L. Proc. natn. Acad. Sci. U.S.A. 83, 342−346 (1986). | ChemPort |
16.	Strzelecka, T. E. & Rill, R. L. J. Am. chem. Soc. 109, 4513−4518 (1987). | Article | ChemPort |
17.	Brandes, R. & Kearns, E. R. Biochemistry 25, 5890−5895 (1986). | Article | PubMed | ChemPort |
18.	Lerman, L. S. Cold Spring Harbor Symp. quant. Biol. 38, 59−74 (1974). | PubMed | ChemPort |
19.	Livolant, F. J. Physique 48, 1051−1066 (1987). | ChemPort |
20.	Demus, D. & Richter, L. Textures of Liquid Crystals (Verlag Chemie, New York, 1978).
21.	Gray, G. W. & Goodby, J. W. G. Smectic Liquid Crystals (Heyden, Philadelphia, 1984).
22.	Lerman, L. S. Wilkerson, L. S., Venable, J. H. & Robinson, B. H. J. molec. Biol. 108, 271−293 (1976). | PubMed | ChemPort |