Polarimetrische Untersuchungen über das Thiol‐Disulfid‐System

II. Kinetics of the Reduction of Wool Keratin by Cysteine

“…It is evident that the rate of stress relaxation, and consequently the rate of the scission reaction, decreases considerably with decreasing pH. This result is in agreement with the studies of Bersin and Steudel [1] ] on cystine and thioglycolic acid. It is probably due, as suggested by these workers, to the effect of pH on the dissociation of the sulfhydryl groups of cysteine, and indicates that the group active in the scission reaction is the CysS-ion.…”

“…On the other hand, it is believed that the value of 18.2 kcal./ mole obtained for the energy of activation is fairly reliable, for it should differ from the correct value only by the heat of ionization of the sulfhydryl group, which is thought to be small. The value of 18.2 kcal./mole obtained here for the cystine-cysteine reaction is close to the value of 11-15 kcal./mole for the cystine-thioglycolic acid reaction measured by Bersin and Steudel [ 1 ] ; but since they were studying the complete reduction (8) and (9), rather than just the first step (8), there is a slight chance that the agreement may be only fortuitous.…”

The Influence of Electrode Potentials on the Extent of Reduction of Cystine in Hair Fibers by Reducing Agents

“…Kubu and Montgomery [4], studying the relaxation of hair fibers in mercaptoacetate solutions, found that the reactions were also first order kinetically. However, the velocity depended on the concentration of RS-ion, as discovered by Bersin and Steudel [1] ] for the reaction of pure 1-cystine and mercaptoacetic acid. Since the RS-concentration depends on the pH, the velocity of the reaction should increase with increasing pH.…”

Mercaptoacetic Acid and Derivatives

“…The strongly reducing nature of mercaptoacetic acid is of importance both in investigations of biochemical redox and enzyme systems and in industrial applications such as cold-waving preparations and modification of wool. The use of mercaptoacetic acid for the permanent waving of hair is based on the reductive cleavage of the cystine disulfide bridges of keratin [7].…”