Phosphatidylinositol 4,5-bisphosphate, PI(4,5)P2, typically resides in the inner leaflet of the plasma membrane of living cells and is involved and a wide variety of biological processes. These range from serving as a second messenger to facilitating cytoskeletal attachment. As such, it is important to explore the behavior of this lipid in model membrane systems to obtain molecular level details on how it interacts with other lipids, membrane-bound proteins as well as aqueous proteins. PI(4,5)P2 is highly charged at physiological pH and protrudes above the plane of the membrane surface. As such, it interacts strongly with divalent metal cations like Mg2+ and Ca2+. In this talk, we will employ supported bilayer systems to explore the mechanisms concerning how this lipid can interact with its external environment. Vibrational sum frequency spectroscopy, fluorescence microscopy, and related interfacial diagnostic results will be provided.-Dr. Paul Cremer