Titration with p-mercuribenzoate PMB

Reaction of thiols with organomercurials 3.8.12.1. Titration with p-mercuribenzoate (PMB) 

1 ml of 0.04 M NaOH, the solution is made up to 25 ml with water, and centrifuged to remove particulate material. This solution (approximately 8 X 10 M PMB) should be stored at room temperature in the dark. Prior to use, the exact concentration of the reagent is determined by measuring the absorbance of diluted solutions obtained by adding 0.5 ml of the stock solution of PMB to 9.5 ml of 0.33 M sodium acetate buffer at pH 4.6 (c= 1.74 x 10 M cm at 234 nm). 

An excellent detailed discussion of the application of PMB to the determination of sulfhydryl groups in native proteins has been presented by Benesch and Benesch (1962). 

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