Sulfur in Proteins

The recent striking advances in our knowledge of protein structure have been made possible in part by the application of methods for chemically modifying selected functional groups. Sanger's use of 2,4-dinitro-lfluorobenzene to mark terminal and side-chain amino groups is an obvious example, and it is worth remembering that the numerous chemical methods for the detection or determination of amino acids residues in intact protein depend on specific chemical reactions of the residue in question. In this paper it is proposed to review briefly some of the more specific methods for effecting chemical changes in the thiol and disulfide groups, with special reference to any disadvantages or limitations, and to present some new results in regard to certain of these methods.