Controlling the Morphology of Chiral Lipid Tubules

Several techniques for controlling the morphology of self-assembled lipid tubules are investigated by using circular dichroism spectroscopy and electron microscopy. These studies show that variations in the molecular structure of the diacetylenic phospholipid, lipid concentration, and solution conditions allow for control of the number of bilayers in the tubule walls, but not their diameter. Tubules formed in water and mixtures of alcohols adopt interesting morphologies and allow for further control of tubule structure. In addition, studies of lipids with different acyl chains show that tubule morphology is sensitive to the degree of order within the chains. Because of the chiral molecular architecture in lipid tubules, intense peaks in their circular dichroism spectra are observed. These peaks can be monitored to obtain information on the tubule morphology. This information is correlated to direct observations made using electron microscopy. Results of these studies have led to the optimization of large scale preparations of tubules for technological applications.