title: Internal structural changes in keratin fibres resulting from combined hair waving and stress relaxation treatments: a Raman spectroscopic investigation.
abstract: OBJECTIVE
  The objective of our research was to investigate the influence of chemical treatments (reduction, stress relaxation and oxidation) on hair keratin fibres.
  
  
  METHODS
  The structure of cross-sections at various depths of virgin white human hair resulting from permanent waving treatments with stress relaxation process was directly analysed at a molecular level using Raman spectroscopy. In particular, the three disulphide (-SS-) conformations in human hair were compared by S-S band analysis.
  
  
  RESULTS
  The gauche-gauche-gauche (GGG) and gauche-gauche-trans (GGT) contents of -SS- groups remarkably decreased, while the trans-gauche-trans (TGT) content was not changed by performing the reduction process with thioglycolic acid. In addition, the high-temperature stress relaxation process after reduction accelerated the disconnection of -SS- (GGG and GGT) groups in the human hair, while the low-temperature stress relaxation process after reduction accelerated the reconnection of -SS- (GGG and GGT) groups. Moreover, the S-O band intensity at 1042 cm(-1) , assigned to cysteic acid, existing in the cuticle region and the surface of the cortex region increased, while the GGG content significantly decreased by performing the oxidation process after the reduction and the high-temperature stress relaxation processes.
  
  
  CONCLUSIONS
  The author concluded that the high-temperature relaxation process after reduction accelerated the disconnection of -SS- (GGG and GGT) groups, thereby leading to the remarkable local molecular disorganization (an increase in the cysteic acid content and a decrease in the GGG content) on the cuticle and cortex cells during the oxidation process.
authors.affiliation: Research and Development Department, Sunny-Place Co., Ltd., 4-6-8, Kuramae, Taito-ku, Tokyo, 111-0051, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kuzuhara
mesh_terms: D006197:Hair; D006801:Humans; D007633:Keratins / Q000737:chemistry*; D015394:Molecular Structure; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D007633:Keratins
keywords: chemical analysis; disulphide (-SS-) conformational changes; hair treatment; internal structural changes; spectroscopy