Alpha Crystal Denaturation Behavior of Human Hairs Treated by the Different Reducing Agents

Abstract

Effects of the reducing agents such as ammonia thioglycolate (ATG), L-cysteine (CYT), cyisteamine (CYA) and 2-mercapto-4-butanolide (BLT) on disulfide (-SS-) cross-links in microstructure surrounding the intermediate filaments (IFs) were investigated by analysis of a crystal denaturation behavior of intact and reduced human hairs using High pressure differential scanning calorimetry (HPDSC) and ambient pressure DSC (APDSC). Their reduced hair samples which sulfhydryl groups caused by a reduction reaction were blocked by N-ethyl maleimide (NEMI) were measured by these DSC techniques. The results have shown that ATG diffuses easily into the cortical cells and then dissociates some -SS- linkages in microstructure surrounding IFs, in contrast, and that the other reducing agent hardly acts to cleave the -SS- bonds in microstructure surrounding IFs. However, it was found that if the cortical cells mechanically crushed using the rotary speed mill were treated with CYT, CYT diffused easily the cortical cells and then dissociated some -SS- cross links in microstructure surrounding IFs. It has been believed from the above findings that CYT, CYA and BLT acts primarily to attack the -SS- bond in the cuticle cell layer. When comparing of the -SS- + -SH groups contents of hair samples reduced with ATG and CYA for different time, it was revealed that -SS- + -SH groups contents of both treated hair became almost constant at 10 min treatment, and furthermore that the equilibrium value of the ATG treated hair was only slightly higher than that of the CYA treated hair. This finding suggested that the amount of -SS-bond cleavage in the cortical cells by ATG treatment was considerably less. As a result of evaluating the permanent wave shape formed by the reducing agent of four under certain conditions based on the knowledge obtained above, it is concluded as follows: (1) Permanent efficiency of wave shape is attributed to the rearrangement of the molecular chains that make up the cuticle cell, which is induced by the -SS- linkage cleavage of exocuticle generating a strain by being wrapped on the rod. (2) The difference of the wave efficiency depending on the type of the reducing agent is due to differences in the permeability of these into cuticle cells.