NEW PH-SENSITIVE AMINOXYLS - APPLICATION TO THE STUDY OF BIOMEMBRANE TRANSPORT PROCESSES

An EPR method for studying transmembrane proton transport using pH-sensitive aminoxyl radicals has been developed for applications in the pH region 4-7. To this end pH-sensitive spin-labelled dextran (pK = 6.1) and sulfonic acid (pK = 5.25), which do not penetrate phospholipid membranes, were synthesized. Using EPR spectroscopy these probes were used to measure the kinetics of pH variations inside large unilamellar phospholipid vesicles after creation. of a transmembrane proton gradient. Membrane permeability coefficients for H+ (5 x 10(-4) cm s-1), Cl-(10(-10) cm s-1) and Tl+ (10(-8) cm s-1) were estimated.