Thioglycolic acid Sulfhydryls

Actual compound formation also occurs between the dehydroascorhic acid and GSH reactants, though little attention has been paid to this condensation. Complexes of dehydroascorhic acid with one molecule of either GSH or thioglycolic acid were formed by Drake et al. (D19) in acetic acid solutions. Disappearance of iodine-titrable -SH groups and appearance of a new levorotatory material indicated the complex formation. This continued until an equilibrium was reached in about one hour at 0°C. At equilibrium more than half the dehydroascorhic acid was complexed. Remarkably little reduction of dehydroascorhic by the sulfhydryl compound occurred, since this reaction becomes significant only at neutral pH s. The complex is probably a thiosemiacetal, similar to... 

Specificity—Crook (41) reported that cysteine and thiolacetic acid could be substituted for GSH. The enzymatic reaction rate Avith cysteine Avas about half as great as the reaction rate AA ith GSH. With thiolacetic acid, the enzymatic reaction AA as only a little faster than the reaction in the absence of enzyme. Bukin (19), on the other hand, reported that sulfhydryl compounds such as thiolactic and thioglycollic acid could not substitute for GSH. Yamaguchi and Joslyn (51) were unable to measure an enzyme reaction AA ith cysteine and thioglycolate becau.se of the high blank reaction rate. They reported that dehydro-D-araboascorbic (dehydro-D-isoascorbic)... 

Examples of alkyl sulfhydryl-bearing compounds that can covalently attach to a chitosan backbone are cysteine, A-acetylcysteine, thioglycolic acid, and glutathione. These molecules become linked to the chitosan primary amino group via an amide bond. 

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