Reactivity in microemulsion media: Oxidation or reduction of cystine residues in keratin

Abstract

The oxidation or reduction of cystine residues of keratin fibres by chemical agents incorporated in microemulsions of a model system was investigated. The microemulsion yielding system water/sodium dodecyl sulfate/1-pentanol/n-dodecane was selected for the following reasons: (a) At values of SDS/C₅OH mass ratio of 1/2 or so, the microemulsion domain in a pseudo-ternary diagram spans a wide range of compositions; (b) The extent and general configuration of the microemulsion domain are not significantly affected by the additon of chemical agents such as thioglycolic acid or hydrogen peroxide nor by temperature changes in the range 20°C–50°C. It was found that the reactivity of cystine, as evaluated by the amount of cysteic acid formed (hydrogen peroxide as reagent), or of cysteine formed, (thioglycolic acid as reagent), could be related to the microstructure of the microemulsions used as the reaction media.