ESR study of proton transport across phospholipid vesicle membranes.
A new method for measuring the rates of proton transfer through bilayer phospholipid membranes using pH-sensitive nitroxyl radicals is suggested. The pH-sensitive alkylating radical was covalently bound to glutathione. This modified glutathione is pH sensitive at pH 1.5-4.5 and does not penetrate across phospholipid membranes. Using ESR this probe was applied to register the kinetics of pH variations inside large unilamellar phospholipid vesicles after creation of a transmembrane proton gradient. In the acidic region (pH approximately 3) the main mechanism of transmembrane proton transfer is that via transport of a proton in the form of an undissociated acid. The membrane permeability coefficients have been determined for a series of acids (HCl, HClO4, HNO3, upper estimate for H2SO4). Taking into account that imidazoline and imidazolidine nitroxyl radicals can be used as pH probes in a wide range of pH, the present method can be developed for measuring the rates of transmembrane proton transfer in neutral and alkaline media.
Khramtsov
V V
VV
Institute of Chemical Kinetics and Combustion, U.S.S.R.
Panteleev
M V
MV
Weiner
L M
LM
D001692:Biological Transport; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers; D008081:Liposomes; D008962:Models, Theoretical; D010713:Phosphatidylcholines; D011522:Protons
D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D011522:Protons