The extent of reduction of wool proteins by thiols

Abstract

The extent of reduction of disulphide groups in Merino wool by dilute solutions of thiols in aqueous alcohols at 20 �C has been studied by carboxymethylation of the reduced wool and estimation of the residual disulphide in the product. The wool fibres remain intact throughout the process. Under these conditions toluene-ω-thiol was the most effective agent giving 93% reduction in 2 days, and more than 99% reduction by repeated reduction-carboxymethylation cycles. With Lincoln wool 100% reduction was achieved.

Regulation of hard α-keratin mechanics via control of intermediate filament hydration: matrix squeeze revisited

“…Methyl iodide creates S-carboxy-methylcysteine from free cysteine residues, blocking future cross-linking from occurring in an oxidative environment [26]. At least 50 ml of each solution was used for each 0.5 g of keratin material, in order to maximize reduction [23]. After methylation, samples were again washed with a 50 per cent 1-propanol solution to remove any remaining chemical agents.…”

“…We disrupted the keratin matrix using an established protocol which cleaves disulphide bonds and prevents their reformation via methylation of free thiol groups [23]. All samples were first treated with acetone to degrease surface lipids [24], which, when left intact, inhibited penetration of the reducing agent in preliminary trials.…”

“…Samples were subsequently washed with a 50 per cent 1-propanol solution to remove any remaining 2-mercaptoethanol. After the reduction process, samples were quickly transferred (to minimize oxidation of cysteine) to a solution of 0.1 M methyl iodide in 0.2 M boric acid buffer at pH 8.0 for 24 h [23]. Methyl iodide creates S-carboxy-methylcysteine from free cysteine residues, blocking future cross-linking from occurring in an oxidative environment [26].…”

Extraction of Reduced Wool Proteins by Solutions of Salts

“…Selective adsorption of anions by the fibre has been proposed (Crewther and Dowling 1956) and this would confer an overall negative charge and tend to disrupt the secondary structure of the proteins. The marked influence which mixtures of aqueous and organic solvents exert on the physical properties (Atkinson and Speakman 1964;Zahn 1964) and on the chemical reactivity (Maclaren 1962;Gerthsen and Meichelbeck 1965) of wool, may also contribute to the dispersion of the keratin fibres.…”

“…It has been shown earlier that the disulphide bonds in wool fibres are reduced specifically and almost quantitatively in aqueous solution using toluene-w-thiol (Maclaren 1962) or tributyl phosphine (Sweetman and Maclaren 1966;Maclaren, Kilpatrick, and Kirkpatrick 1968). The next step was to find a suitable solvent system to extract the proteins from the reduced fibre.…”