9728206 Feller Atomic-level computer simulations will be used to probe the structure and dynamics of bilayer membranes containing a variety of phospholipids, as well as small solutes, nonionic surfactants, and peptides. Because of the inherent disorder in the liquid-crystalline phase in which lipids exist at physiological temperature, atomic level structural data are extremely difficult to obtain experimentally. Thus these simulations will complement the existing body of experimental data. These experimental data will be used in two ways for this project. Where possible, comparison will be made between properties observed in the simulation with those obtained experimentally in order to test the validity of the work. Secondly, many of the analyses of these simulations have as their goal the extraction of bilayer properties which can be utilized in the interpretation of experiments. The specific objectives of this research are the determinations of the volumes of fragments of lipid molecules with a precision not available experimentally. These data will be used to introduce packing models into the interpretation of membrane diffraction experiments. The fraction of free or void volume associated with each fragment will be determined. This will address the role played by specific parts of the lipid in the permeation of the membrane by small solutes. This project has biological relevance because of the importance of bilayer membranes to cell structure and function. This work will provide a detailed picture of bilayer systems at the atomic level, and will provide information on the roles of specific parts of the lipid in permeation. ***
