Sulfhydryl Groups in Proteins Iii. the Effect on Egg Albumin of Various Salts of Guanidine by Jesse P. Greenstein

The denaturation of certain proteins is characterized in part by the appearance of titratable sulfhydryl groups (8,11, 13).’ Moreover, the proportion of these groups which appears in any one protein is dependent upon the method of denaturation employed (3,5,6). Proteins dissolved in solutions of urea, guanidine hydrochloride, and related substances show widely different amounts of sulfhydryl groups which depend on the nature and the concentration of the reagent. For all of the proteins investigated, the greatest proportion of titratable sulfhydryl groups appears in solutions of guanidine hydrochloride.2 From studies of a single guanidine salt, it is difficult to assess the contribution to the denaturation of protein by either the cation or anion. That certain anions are capable of serving as denaturing agents is evident, for example, from the long noted effect of iodide, thiocyanate, and salicylate on proteins (10, 12). In order to compare the relative effects of a number of anions, the present investigation was extended to egg albumin dissolved in several guanidine salts.