This project will use multi.dimensional X.ray diffraction techniques to obtain high resolution molecular structures of polymerizable lipids in hydrated bilayers. It will determine the relationship between molecular structure of lipid monomers and the ultrastructures they form. The focus will be on diacetylenic phosphatidylcholines, which form tubular ultrastructures which do appear by some criteria to have a nearly crystalline lattice structure, but do not polymerize as well as other diacetylenic molecules. The investigator will also attempt to develop a rational theory for the formation of chiral tubules and identify the structural parameters which promote optimal diacetylenic polymerization of amphiphilic diacetylenes. Polymerizable lipids are surfactants with a reactive group that allows surfactant monomers to be cross.linked by chemical or photochemical catalysis. The liposomes or films formed by these lipids are thereby more robust than those made of conventional lipids and may be more effective in a variety of applications such as synthetic membranes for separations and chemical sensors, thin films for new electronic devices, and biomedical applications. In addition, they are good model systems for the study of the physics of biological membranes. ____________________________ ____________ Program Director's Signature Date//
