Research Projects

The cell is the basic unit of life, with numerous compartments for various physiological activities. It is covered with a bilayer membrane, a semipermeable membrane that allows the cell to perform various functions. The cell membrane's properties are largely dependent on lipid composition, with around 1000 different lipid species in mammalian cells. These lipids vary in head group size, charge, acyl chain lengths, and degree of saturation. Outer leaflet lipid-tethered proteins, such as Glycocosylphosphatidy inositol anchored proteins (GPI-APs), are organized as monomers and sphingomyelin-cholesterol sensitive nanoclusters, regulated by the actin-myosin complex at the cortex. Phosphatidylethanolamine (PE) and phosphatidylserine (PS) are found more in the inner leaflet of the bilayer membrane, while sphingomyelin (SM) lipids are found more in the outer leaflet. Sterols regulate fluidity by interfering with acyl chain packing of lipids, and can increase the rigidity of the membrane if they contain unsaturated lipids with flexible acyl chains. The primary challenge in cell membrane biophysics is understanding the physical and chemical basis of lipid/protein organization and segregation in different scales involving functions such as sorting, signaling, and endocytosis. This includes understanding why there is an immense compositional diversity of structural lipids, how they are maintained homeostatically, how they are altered in disease conditions, and how lipid diversity affects the physical and chemical properties of the cell membrane.