Electro and Magnetooptic Studies of Phospholipid Tubules

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Under appropriate conditions of temperature, concentration and pressure, phospholipids organize into a variety of interesting and potentially useful structures, including flat lamellae, elongated rodlike structures, and closed vesicles. These vesicles range in dimension from hundreds of angstroms to tens of microns and consist of bilayers separated by an aqueous medium. A new structure composed of a polymerizable diacetylenic phospholipid was recently discovered by a joint Naval Research Laboratory/Geo-Centers group. Below 39 C pieces of bilayer assemble into straight, hollow tubules in a form similar to a roll of aluminum foil. A number of magneto-and electrooptic experiments are planned with these materials. Cotton-Mouton measurements will be made on dilute suspensions of tubles in order to better understand the molecular orientation with the tubule. At higher concentrations, birefringence and light scattering will be used to determine the interparticle potential of tubules in suspension, both the short and long range parts. In addition, an attempt will be made to locate a liquid crystal nematic phase which, if successful, will be complemented with studies of the mechanical properties and possible non-linear optical response. Finally, a number of different studies will be made involving tubule manipulation.