Transvesicular Reactions of Thiols with Ellman's Reagent

Article abstract of DOI:10.1021/jo00260a013

The cleavage of Ellman's reagent <5,5'-dithiobis(2-nitrobenzoic acid)>, 1, to chromophoric anion 2 by various thiols has been studied in pH 8 buffer, micellar cetyltrimethylammonium bromide (4), and vesicular dihexa-decyldimethylammonium bromide (5) or dioctadecyldimethylammonium chloride (6) solutions.The thiols included thiocholesterol, thiophenol, 2-thionaphthol, DL-cysteine, glutathione, 1-butanethiol, and 1-octanethiol.Vesicles of 6 at 25 deg C sequester 1 in distinct exovesicular and endovesicular binding sites, where reactions with added thiols are kinetically differentiated.Differences in thiol acidity and structure influence their rates of permeation and reaction with vesicle-bound 1.Small quantities of covesicallized 1-hexanol (0.2 wt percent) lower the gel to liquid crystalline transition temperature of vesicular 1 (from ca. 39 deg C to 24 deg C), enhance vesicular fluidity, accelerate the thiol/1 reactions, and destroy the kinetic distinction between the exovesicular and endovesicular reactions.