The reducing power of cysteine

Abstract

Cysteine cannot reduce indigo carmine and cystine cannot oxidize reduced indigo carmine or reduced indigo in the absence of a 3rd component, which functions as an activating agent and which is produced through the action of O or NaHS on indigo carmine. Fe cannot activate the[long dash]SH or[long dash]SS grouping, but it markedly influences the velocity of reaction between 0 and indigo carmine. This results in an increased concentration of the activating agent. Agitation of the solution and other physical factors influence the formation of the activating agent which is destroyed by heat. Fe neither accelerates nor prevents the action of NaHS on indigo carmine. The activating agent appears to be an unstable O or S addition product of indigo carmine, and its essential action involves the activation of the S atom, which permits the sulphydryl and disulphide groupings to manifest their latent reducing or oxidizing power. In the presence of a constant concentration of the activating agent, the velocity of oxidation and reduction is determined by the ratio C [image] SH/C [image] SS [image] C groupings.