Examining The Role Of Lipid Variations And Proteins On Membrane Biophysics: Synthetic Versus Natural Membrane Vesicles

Biomembranes in living cells are complex, heterogeneous and dynamic systems that regulate numerous biological processes such as cell signaling, endocytosis and exocytosis, and protein trafficking. Cholesterol-rich lipid domains have been hypothesized to exist in a liquid-ordered phase and play an important role in cellular functions. Here, we test the hypothesis that cholesterol diffuses as a complex with other lipids in a bilayer. In addition, we examine the role of lipid variation and proteins on the biophysical properties of biomembranes using comparative studies of giant unilamellar vesicles (GUVs) and plasma membrane vesicles (GPMVs) isolated from Hs578Bst live cells. The fluorescence dynamics assay used here includes two-photon fluorescence lifetime imaging, fluorescence resonance energy transfer, and diffusion (both rotational and translational). Different fluorescent lipid analogs are used in these studies to probe both the hydrophobic core and the head group region. Our comparative studies on GUVs and GPMVs serve as a platform to test our understanding of lipid-lipid and lipid-protein interactions in these biomembrane models.