Time-resolved proton-phospholipid interaction. Methodology and kinetic analysis

Esther Nachliel, Menachem Gutman

Research output: Contribution to journalArticlepeer-review

Abstract

The proton transfer between bulk and phospholipid surface was measured at real time by the laser induced proton pulse method. (Gutman, Methods Biochem. Anal. 1984, 30, 1-103). A pH indicator was adsorbed either on phospholipids—Brij-58 mixed micelles or on small unilamelar liposomes, and the protonation dynamics were recorded. The probe reactions are sensitive to the composition of the surface; its rate and extent of protonation vary with the surface density of the phospholipids and their pK. The observed transients were analyzed by numerical solution of coupled differential equations. The solution determines the rate constants of the phosphohead groups protonation and the rate they exchange protons with the probe. Through this analysis we can account for the capacity of the membrane to function as proton-collecting anthena; the protons first react with the acidic, ionized moieties on the surface and then, by rapid exchange, reach the strongest base on the surface. Both trapping capacity and rate of flux between surface groups are affected by the pK. Proton trapping is enhanced by less acidic lipids like phosphatidylserine (pK = 4.6). Proton mobility is enhanced by more acidic groups like phosphatidylcholine (pK = 2.2). This analysis predicts how combination of the two effects will determine apparent reactivity of a probe on phospholipid membrane.

Original languageEnglish
Pages (from-to)2629-2635
Number of pages7
JournalJournal of the American Chemical Society
Volume110
Issue number8
DOIs
StatePublished - Apr 1988

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