Determination of Disulphide Groups in Proteins

Abstract

RELATIVELY simple methods are available for the determination of sulphydryl groups in proteins¹. The determination of disulphide groups is, however, more difficult and the methods available are more laborious and less accurate. Most of the methods used for the determination of disulphide groups are based on the reduction of these groups followed by amperometric determination of liberated thiols². Alternative to these procedures are those using exchange with dinitrophenylcystine³, oxidation with performic acid⁴, or reduction and alkylation with mono-iodacetate⁵. This communication deals with the method recently used in our laboratory for the determination of disulphide groups using sodium borohydride (NaBH₄) in 8 molar urea as reducing agent^6,7 and 5,5′-dithiobis (2-nitrobenzoic) acid (DTNB) as a thiol disulphide exchanger⁸.