National Synchrotron Light Source Seminar

Small-angle Neutron Scattering (SANS) has been used to study the structure, function and dynamics of complex biological systems. With the selective deuterium labeling and contrast variation techniques, SANS is capable of distinguishing one component of the complex from the rest of it without changing the structure and function of biomolecules in biological relevant solution condition. This talk will present two recent studies on lipid vesicle bilayer structure and protein structure under crowding conditions, respectively. In the first study, the result shows that two membrane-active peptides alamethicin and melittin induce asymmetric distribution of charged lipids, enriching the outer leaflet of bilayer with negatively charged lipid. It suggests that these peptides may have a secondary stressful effect on target cells at even low concentrations. In the second study, the structure and oligomerization state of green fluorescent protein (GFP) were investigated under crowded conditions created by another protein human serum albumin (HSA). By using perdeuterated GFP and hydrogenated HSA, I am able to probe only the GFP in the solutions by contrast matching HSA with an appropriate D2O/H2O buffer mixture. Analysis of the data indicates that GFP undergoes an HSA concentration-dependent transition that alters the way in which GFP oligomerizes in the solution.