Biophysical Journal 50: 265-276 (1986)
© 1986 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Grzesiek, S Articles by Dencher, N A Search for Related Content PubMed PubMed Citation Articles by Grzesiek, S Articles by Dencher, N A

Dependency of delta pH-relaxation across vesicular membranes on the buffering power of bulk solutions and lipids.

ABSTRACT

The dependency of delta pH-relaxation kinetics across the membrane of sonicated small phospholipid vesicles on the concentration of internally entrapped buffer has been investigated by means of the pH-indicator dye pyranine. A very high contribution of lipid headgroups to the internal buffering power of the liposomes is observed, amounting to an equivalent phosphate buffer concentration of 110 mM. This localized two-dimensional proton/hydroxide ion reservoir must be considered in any determination of the H+/OH- permeability coefficient. Furthermore, it could have significance for energy-transduction across biological membranes. From the established linear relation between delta pH-relaxation rates and buffering power, net H+/OH- permeabilities of 3 X 10(-3) cm/s for soybean phospholipid (SBPL) and 1 X 10(-4) cm/s for diphytanoyl phosphatidylcholine (diphytanoyl PC) vesicles at pH 7.2 as well as buffering powers per lipid molecule of 6 X 10(-2) (pH-unit)-1 (SBPL) and 4 X 10(-2) (pH-unit)-1 (diphytanoyl PC) are calculated. In the case of diphytanoyl PC vesicles, delta pH-decay is accelerated by the presence of chloride ions.