Abstract
Symmetric thiamine disulfides such as TDS, BTDS, PrTDS or BuTDS and asymmetric thiamine disulfides such as TBzD or TPD were found to be useful as the reagents for determination of SH groups. Stoichiometry, specificity, and sensitivity were tested with cysteine and glutathione and a standerd procedure was established. Usually 0.1〜0.2 μmoles of SH was incubated with 5 μmoles of TDS in the presence of EDTA at pH 6〜9 (optimal 7〜8), 30℃ for 5〜30 minutes, and the amounts of SH was calculated from the amounts of free thiamine liberated. In microprocedure, 0.002 μmoles thiol could also be determined with considerable accuracy. Sulfhydryl contents of ovalbumin, bovine serum albumin and β-lactoglobulin, determined by this method after sufficiently denatured, were confirmed to agree with those obtained by the Boyers' PCMB method. Reactivity between protein-SH and these thiamine disulfides as well as some possible use of the method were discussed.
