9710795 The organization of the enzymes that work at biological membrane surfaces will be studied by combining expertise in chemistry, physics and biology. Indirect measurements suggest that their activity may be determined by their arrangement (single, dimeric or aggregated) and by the length of time they spend at the surface. In turn, the organization and dwell time of the enzyme is altered by the lipid composition of the membrane. The goal is to directly observe the state of these enzymes under a variety of conditions using scanning probe microscopy (SPM), and to correlate these results with their catalytic properties measured under similar conditions. Robust models of biological membranes suitable for examination by SPM will be developed. Then these model systems will be adapted for measuring enzyme activities and the membrane state using optical spectroscopy and electrochemical techniques. Preliminary experiments conducted by undergraduate students and faculty show that the methods proposed are feasible and the information obtained will address a fundamental question about how cell activities are controlled. Over the life of this project, twenty or more undergraduate students will experience collaborative, interdisciplinary research with sophisticated equipment, addressing problems that could not be solved by a single researcher or discipline alone. Nontechnical Abstract This project focuses on cell membranes, thin layers of proteins and lipids that are crucial structures within and bordering the cells of all living organisms. Cell membranes have many functions including providing a means of organizing other components of the cell and regulating traffic and information flow between the inside and outside of the cell. One can describe the cell membrane in terms of its average composition, but this is not sufficient to tell us how the membrane functions. The tools are just being developed to describe the cell membrane at the level of detai l needed to understand its function. One new technique, scanning probe microscopy (SPM), measures the physical features of the membrane at a molecular scale by probing in a manner analogous to the way the needle of a record player systematically touches the record and converts the small changes in the vinyl to an electrical signal and then to music. This type of probing will allow the description of the membrane at the level of detail necessary to explain at least one of its functions, the control of an important signaling pathway that requires special interactions between a protein and the membrane lipids.
