The reaction of 4-( p-sulfophenylazo)-2-mercuriphenol with the thiol groups of proteins

Abstract

1. 1.|A new water-soluble azomercurial, 4-( p-sulphenylazo)-2-mercuriphenol, has been prepared and tested as a thiol probe. 2. 2.|Upon reaction with the thiol groups of native proteins, the p K of the phenolic group of the reagent underwent a shift depending on the environment of the thiol group. An ovalbumin derivative, containing about 3 moles of azomercurial per mole of protein, showed two p K values for the phenolic group. 3. 3.|Using the large differences in visible absorption between bound and free dye, resulting from the p K shifts, a spectrophotometric thiol titration of β-lactoglobulin could be carried out. The thiol titration of bovine serum albumin was disturbed by adsorption of excess dye.