Response of Lipid Bilayer and Model Membrane Properties to Hydrostatic Pressure
Bilayer responses to hydrostatic pressure reflect competition between lateral compression (favouring chain extension) and longitudinal compression (favouring bilayer thinning). This promotes phases not found at ambient pressure such as interdigitated gel in which lipid chains extend significantly past the bilayer mid-plane. Dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) are two saturated-chain lipids differing at the headgroup. Phosphatidylcholine (PC) is zwitterionic and phosphatidylglycerol (PG) is anionic. In the absence of divalent cations, the phase behaviours of DPPC and DPPG are remarkably similar. We recently found that DPPG is more susceptible than DPPC to pressure-induced chain interdigitation suggesting that electrostatic headgroup interactions shift the balance between lateral and longitudinal compression. We also study how chain unsaturation affects bilayer response to pressure, a question with relevance to pressure accommodation by marine organisms. On comparing lipids with one or two double bonds on the sn-2 chain, we found that greater unsaturation reduced sensitivity to pressure. In work on bilayers containing 1:1 lipid mixtures, we found that the pressure-induced ordering of individual components was coupled to average bilayer order in a way suggestive of self-consistent mean-field interactions. Nasir Uddin is currently studying the effect of pressure on the organization and magnetic orientation properties of disc-like lipid assemblies known as bicelles.
30 Nov -0001
Strategic Research Theme
Information and Communication Technology