The chemical and physical properties of supported lipid bilayers

Lipid-lipid and lipid-support interactions have been investigated using supported lipid bilayers. Experimental results of these interactions will be discussed in six chapters. The first chapter provides an introduction and background to the molecules investigated, experimental system, research objectives, and organization of the thesis. The second chapter provides experimental details and the methodology of the experiments conducted herein. Chapters three through five are based on papers that have been published, or are in submission to be published, as a result of this work, with the addition of some recently obtained results included at the end of chapter five. The final chapter, chapter six, summarizes the overall work that has been done and addresses the future direction of this work

Influence of Lipid Chemistry on Membrane Fluidity: Tail and Headgroup Interactions

Membrane fluidity plays an important role in cell function and may, in many instances, be adjusted to facilitate specific cellular processes. To understand better the effect that lipid chemistry has on membrane fluidity the inclusion of three different lipids into egg phosphatidylcholine (eggPC) bilayers has been examined; the three lipids are egg phosphatidylethanolamine ((eggPE) made by transphosphatidylation of eggPC in the presence of ethanolamine), lyso-phosphatidylcholine (LPC), and lyso-phosphatidylethanolamine (LPE). The fluidity of the membranes was determined using fluorescence recovery after photobleaching and the intermolecular interactions were examined using attenuated total reflection Fourier transform infrared spectroscopy. It was observed that both headgroup and tail chemistry can significantly modulate lipid diffusion. Specifically, the inclusion of LPC and eggPE significantly altered the lipid diffusion, increased and decreased, respectively, whereas the inclusion of LPE had an intermediate effect, a slight decrease in diffusion. Strong evidence for the formation of hydrogen-bonds between the phosphate group and the amine group in eggPE and LPE was observed with infrared spectroscopy. The biological implications of these results are discussed