Effect of vesicle composition and curvature on the dissociation of phosphatidic acid in small unilamellar vesicles--a 31P-NMR study.
Sonicated small unilamellar vesicles (SUVs) containing phosphatidic acid (PA) give two PA 31P-NMR resonances corresponding to PA molecules in the inner and outer leaflets of the bilayer. This NMR differentiation between the two monolayers is not due to a pH gradient across the membrane but instead reflects differential packing in the inner and outer leaflets imposed by the highly curved SUV surface. The apparent pKa of the outer-leaflet PA increases with decreasing surface curvature and with increasing PA content. The estimated relationship between the apparent pKa of the outer-leaflet PA headgroup and vesicle curvature may provide a qualitative probe for effects related to surface curvature in these model-membrane systems.
Swairjo
M A
MA
Department of Physiology, Boston University School of Medicine, MA 02118.
Seaton
B A
BA
Roberts
M F
MF
D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010712:Phosphatidic Acids / Q000737:chemistry*; D013010:Sonication
D008051:Lipid Bilayers; D010712:Phosphatidic Acids