Dinitrophenylation and Thiolysis as a Tool in Protein Chemistry

The thiolytic cleavage of 2,4 dinitrophenyl derivatives of sulfhydryls, imidazole imino‐nitrogens, and phenolic hydroxyls converts dinitrophenylation into a reversible method for masking or labeling these functional groups. The merits of this method are illustrated in the synthesis of peptides and polyamino acids (including a potent synthetic immunogen), in sharpening the specificity of dinitrophenylation, in masking “super reactive” nucleophiles in proteins while labeling “buried” functional groups, and in the probing and three‐dimensional mapping of enzyme active sites. Analytical techniques for monitoring the rate and extent of the thiolysis step are described.