Analysis of Cysteine on the Surface of Hair Fibers with Spectrofluorescence

Many physical or chemical factors can affect the cysteine components in the keratin of human hair,which leads to the rapture of disulfide bonds in cysteine and forms cysteine with mercapto group. Thus the amount of cysteine production can be used as an index to assess the extent of hair damage. In this paper a fluorescence probe, NBD-Cl, was selected to study the formation of cysteine in the surface of hair fibers with spectrofluoresence method. NBD-Cl interact with both the mercapto and amino groups contained in cysteine, resulting fluorescence complexes on the hair surfaces. Reaction conditions were optimized. The highest fluorescence emission was obtained at pH 4.5.