Cystine hydrogenation

Inhibition of monoamine oxidase has been proposed as a possible mechanism underlying the hydrogen sulfide-mediated disruption of neurotransmission in brain stem nuclei controlling respiration (Warenycia et al. 1989a). Administration of sodium hydrosulfide, an alkali salt of hydrogen sulfide, has been shown to increase brain catecholamine and serotonin levels in rats. It has also been suggested that persulfide formation resulting from sulfide interaction with tissue cystine and cystinyl peptides may underlie some... 

The complex catalytic polarographic hydrogen wave of the Irlv cystine complex (31) has been investigated in 1.2 M HC1.26,27... 

Oxidative bleaching of wool is invariably carried out with hydrogen peroxide. The active species involved is likely to be the same as on cellulosic substrates but specific reactions with wool amino acid residues must be considered. The primary reaction is oxidation of cystine disulphide bonds leading to the formation of cysteic acid residues (Scheme 10.41). The rupture of disulphide crosslinks, with attendant increase in urea-bisulphite and alkali solubility values, adversely affects fibre properties. As the severity of bleaching conditions increases, the urea-bisulphite solubility remains little changed but the relationships between alkali solubility and cysteic acid (Figure 10.36) and between cystine and cysteic acid (Figure... 

The hydrolytic breakdown of the disulphide bonds of cystine liberates some hydrogen sulphide and this can gradually deactivate a vinylsulphone dye by formation of the... 

The most convenient oxidant for the preparation of cysteic acid from cystine is aqueous bromine.1 Iodine2 and hydrogen peroxide3 also bring about the reaction, but with both substances some of the sulfur is split off as sulfuric acid. 

Hu Z, Guan W, Wang W, Huang L, Xing H, Zhu Z (2007b) Protective effect of a novel cystine Cm derivative on hydrogen peroxide-induced apoptosis in rat pheochromocytoma PC12 cells. Chem. Biol. Interact. 167 135-144. 

Neuberg and Popowsky, as also Abderhalden and Kempe, have introduced a few alterations in the procedure, such as evaporation in vacuo, and Levene and Rouiller suggested in 1906 that the tryptophane, on account of its proneness to decompose on evaporation of its solution with consequent loss, be estimated colorimetrically the mercury sulphate precipitate is decomposed, and the solution, freed from hydrogen sulphide, is titrated with bromine water in presence of amyl alcohol. Both cystine and tyrosine react with bromine water the latter can, however, be removed, but for the former a correction has to be made. Up to the present no values concerning the amount of tryptophane in various proteins have appeared, and it will be of interest to see if the values so obtained are very much higher than those obtained by crystallisation of the tryptophane. 

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