Structure of Lipid Membranes at Solid / Liquid and Liquid / Vapor Interfaces

STRUCTURE OF LIPID MEMBRANES AT SOLID/LIQUID AND LIQUID/VAPOR INTERFACES C. M. DeCaro, Ph.D. Department of Physics Northern Illinois University, 2012 Laurence Lurio, Director The study of model lipid membranes is one of the most promising and exciting areas of current biophysical research. The physical processes that occur in a cell’s outer membrane regulate all transport in and out of the cell, and play a large role in many other cellular processes as well, including defense and reproduction. While the big-picture effect of these processes has been known for a long time, the membrane mechanisms responsible for those effects are understood only at a basic qualitative level. Although strong efforts have been made recently to quantify membrane structure and processes, the field is still in a new and adventurous state. Many bioengineering applications of membranes are also being explored, particularly in which a membrane is supported by a rigid semiconductor such as a silicon wafer. The goal of this work is to examine the structure of these membranes at planar interfaces. I investigate model membranes at both solid/liquid and liquid/vapor interfaces; relevant membrane compositions and preparations are also considered. I use a novel technique to deposit multiple discrete lipid membranes on planar solid substrates; the structure of the membrane normal to the substrate plane yields information about the interaction between the membrane and substrate. Most importantly, the substrate exerts an attractive force on the membrane, suppressing thermal fluctuations in the membranes near the substrate surface. This substrate confinement effect is important to any potential supported-membrane structure. Membranes free from a rigid support are studied at the liquid/vapor interface, where the effect of lipid composition on domain formation is investigated. NORTHERN ILLINOIS UNIVERSITY DE KALB, ILLINOIS