About the Seminar:
Phosphatidylinositol 4,5-bisphosphate, PI(4,5)P2 is one of the most negatively charged lipids in the plasma membrane of living cells with a net charge ranging from -3 to -5 near physiological pH. The phosphate moieties on this lipid bind tightly to divalent metal cations including Ca2+ and Mg2+. Herein, we use a variety of spectroscopies and microscopies to investigate the behavior of PI(4,5)P2. For example, it can be shown by vibrational sum frequency spectroscopy that Ca2+ has a far larger influence on the orientation of the inositol ring compared to Mg2+. This is the case because Ca2+ can shed its inner hydration shell to bind directly to the negatively charged phosphate moieties and link them together. Moreover, PI(4,5)P2 has a strong influence on interfacial water structure. Several biological mechanisms involving this lipid will be discussed. These will include its role as a second messenger as well as its ability to aid cytoskeletal attachment.