Department of Physics & Astronomy

Abstract:
Many essential biological processes depend on the interaction of lipids, proteins, and carbohydrates at length scales that are unresolvable by conventional optical microscopes. We are developing novel optical methods to elucidate the interdependence of molecular organization, lipid phase, and membrane curvature. With near-field fluorescence cross-correlation spectroscopy, we have resolved the single-molecule cross-linking of membrane proteins in the initial stage of an immunological response on living cells. With polarized localization microscopy, we have measured membrane curvature as small as 20 nm radii of curvature and correlated molecular reorganization. Recently,
we have discovered that cholera toxin subunit B self-assembles to form nanoscale membrane buds in quasi-one component bilayers to facilitate its immobilization and internalization into cells. We will discuss the physics of these optical methods and what they have taught us about the biophysics of membranes.