title: A fluorescence quenching technique for the measurement of paramagnetic ion concentrations at the membrane/water interface. Intrinsic and X537A-mediated cobalt fluxes across lipid bilayer membranes.
abstract: We have characterized the quenching of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine by Co2+ in egg phosphatidylcholine (PC) lipid bilayer vesicles. The quenching constant obtained is 59 M-1. We demonstrate one use of this fluorescence quenching technique by measuring intrinsic and X537A-mediated transmembrane Co2+ fluxes in large unilamellar PC vesicles. The intrinsic rate constant for Co2+ flux we measure is 3 X 10(-6) S-1. We confirm that the neutral Co approximately (X537A)2 complex is the main component of the X537A-mediated cobalt flux. Since this method measures the concentration of Co2+ at the site of the fluorophore, it is generally applicable to the measurement of paramagnetic ion concentrations in the region of the membrane/water interface.
authors.forename: R
authors.initials: R
authors.lastname: Homan
authors.forename: M
authors.initials: M
authors.lastname: Eisenberg
mesh_terms: D003035:Cobalt / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005453:Fluorescence; D007832:Lasalocid / Q000494:pharmacology*; D008051:Lipid Bilayers / Q000378:metabolism*; D008433:Mathematics; D008956:Models, Chemical; D010539:Permeability; D013997:Time Factors; D014867:Water
chemical_list: D008051:Lipid Bilayers; D014867:Water; D003035:Cobalt; D007832:Lasalocid