Determination of -SH and -SS- groups in protein—II The age-dependence of -SH and -SS- contents in the soluble protein fractions of the eye lens

Abstract

Sulfhydryl and disulfide groups in the crystallins, the soluble protein fractions of the eye lens, were determined using the polarographic estimation of methylmercuric iodide after an excess of this reagent had reacted with the proteins. The results show that for one of these fractions, the γ-crystallins, -SH groups progressively decrease with age but that the total half-cysteine content, present as -SH and -SS-, remains approximately constant. Further, there are indications that exposure to ionising radiation causes different changes than those brought about on aging. Finally the precipitation process, which occurs when solutions of γ-crystallin are allowed to stand in pH7 buffer in the absence of air, does not appear to involve conversion of -SH to -SS- groups.