CAREER: Self-Assembly of Polyunsaturated Lipids and Cholesterol In The Cell Membrane

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This Career award by the Biomaterials program in the Division of Materials Research to Florida State University investigates the self-assembly of cholesterol and polyunsaturated lipids in the lipid bilayer and their structural effects on the cell membrane. This proposal is to develop understanding of the fundamental physics behind the cell membrane, and will undoubtedly lead to new medical technologies in the future. In addition, self-assembled biological structures can be tailored to a variety of applications for templating and the formation of nanostructures. This proposal focuses on the study of membrane systems using grazing incidence x-ray diffraction (GIXD) and resonant x-ray diffraction. Using in-vitro lipid mixtures, the PI will investigate the effects of biologically active molecules on the structure and physical properties of the lipid bilayer. Cholesterol is one of the most important components of the cell membrane, and through interactions with other lipids, it may influence membrane protein function significantly by affecting membrane properties or by inducing phase separation into lipid 'rafts'; areas of the cell membrane with a differing composition to the surrounding regions. In this project, polyunsaturated fatty acids will be incorporated into biologically relevant lipid bilayers and their interactions with cholesterol. This interplay is highly relevant to membrane properties in the retinal rod cell outer segment, where high concentrations of highly unsaturated lipids occur, but their functions are not well understood. To carry out this work, the investigators will use synchrotron x-ray techniques to study bilayer structure in different lipid mixtures, particularly in plane ordering. Fluorescence microscopy and atomic force microscopy will complement this work, giving information on macroscopic membrane structure and phase separation. Despite the importance of biological physics and the relevance of cellular structure to the living organism, undergraduate life-science students remain largely unaware of the physics of bio-molecules and their interactions on the nano-scale, where fundamental forces control the assembly of all supra-molecular structures found in the cell. This proposal aims to introduce students in life-science majors with an aversion to physics, to the world of bio-molecular interactions and their importance. By developing a major new course, "Biomedical Physics", the PI is working to introduce physical science topics to the undergraduate student population in novel, biologically related ways. A key focus is to attract female undergraduate students in life science majors to experience research in physics and to encourage them to pursue a career in biophysics. The PI will also teach an undergraduate course in condensed matter physics that includes more advanced topics in biomolecular assembly and soft matter to the traditional condensed matter topics. These courses will be complemented by the development of a major new web-site "softmatterworld.org" focusing on soft-matter physics, a significant proportion of which will involve biophysics and bio-molecular self-assembly.