Determination of low molecular thiols and protein sulfhydryl groups using heterocyclic disulfides

A promising area in the analytical chemistry of thiol-containing compounds is the use of heterocyclic disulfides as analytical agents, but now only a few of them are widely used. In this paper, we evaluate the possibility of using three different heterocyclic disulfides 2,2'-dithiobis[5-phenyl-1,3,4-oxadiazole] (I), 2,2'-dithiobis[benzoxazole] (II) and 8,8'-dithiobis-quinoline (III) as analytical reagents for the low-mass aminothiols cysteine and glutathione determination. The optimal analysis conditions were found. Spectrophotometric, kinetic, CE, and HPLC methods using I, II, III for the determination of cysteine and glutathione were developed. The obtained methods are characterized by accuracy and sensitivity (detection limits in the range of 10^-5-10^-6 M) sufficient to quantify cysteine and glutathione in their physiological concentrations. Finally, the proposed disulfides were used to determine the SH-content in the bovine serum albumin (BSA). Considering a number of criteria (applicable pH range, absorption properties, susceptibility to hydrolysis) it was concluded that the proposed reagents have advantages over the commonly used ones (such as the Ellman reagent).