Photolysis and Photo‐oxidation of Amino Acids and Peptides—vi. A Study of the Initiation of Disulphide Interchange by Light Irradiation

Abstract

Abstract— Investigations concerning the occurrence of disulphide interchange for disulphides related to cystine are made with either a single unsymmetrical disulphide or an equimolar mixture of two symmetrical disulphides. It is found that in the pH range 1–6 where spontaneous interchange can usually be disregarded, interchange can be initiated by the addition of a small amount of a thiol or by irradiation with ultraviolet light from either of two artificial sources, interchange being more rapid at pH 4–6 than at pH 1–3. Direct sunlight and, to a lesser extent, visible (filtered tungsten) light are also effective. Disulphide interchange in the solid state can also be promoted by ultraviolet light. A comparison is made between the roles' of S‐S and C‐S bond fission in the photochemistry of disulphides, with respect not only to the promotion of disulphide interchange, but to other phenomena such as the dismutation of disulphides to thioethers and trisulphides.

Reactions of thiyl radicals. III. Photochemical equilibrium in the photolysis of liquid disulfide mixtures

“…When two different disulfides are co-photolyzed, reaction [3] will give rise t o the cross product (in the present system, CH3S2C2H5). As the concentration of this product increases in the system it will begin to compete effectively for absorption of the incident radiation, and its photolysis will become an important source of both methyl and ethyl thiyl radicals.…”

Chemistry of Bifunctional Photoprobes

“…Hydrolysis of 2 by 30% NaOH gives rise to the corresponding acid 3 which can be activated to the corresponding succinimide 4 using DCC. The introduction of an S-S cleavable bond is achieved by reaction of 4 with 3-[(2-aminoethyl)dithio]propionic acid 5, prepared by a method found in the literature (24). In the last step, activation of the carboxylic group by the sodium salt of sulfosuccinimide in DMF lead to a chromogenic, cleavable, water soluble, and bifunctional cross-linker 7.…”

Artificial Light‐sensitive Enzymatic Systems as Chemical Amplifiers of Weak Light Signals

“…For the catalytic activity of papain to be displayed, it should be activated, for example, chemically (with such activation the S-S bond breaks up). In principle, S-S bonds both in peptides and proteins may be cleaved not only chemically, but photochemically (Eager and Savige, 1963 Asquith and Hirst, 1969). This was used by Dose and Risi (1972) for photochemical activation of papain; in a solution of papain-S-S-ysteine illuminated with UV light a catalytically active enzyme is formed (13) This approach was modified in work (Kazanskaya and Nikol'skaya, 1975) where a disulphide dimer of the enzyme, papain-S-S-papain, was obtained as a result of oxidation of active papain catalyzed by copper ions.…”