title: Secondary structure estimation and properties analysis of stretched Asian and Caucasian hair.
abstract: BACKGROUND
  In this previous work, we investigated the secondary structure changes of stretched yak hairs by deconvolution, secondary derivation, and curve fitting and determined the number of bands and their positions in order to resolve the protein spectrum of Raman spectroscopy.
  
  
  OBJECTIVE
  The secondary structure estimation and properties analysis of stretched Asian and Caucasian hair were investigated by Fourier transform infrared spectroscopy, tensile curves, and measurement of density.
  
  
  METHODS
  The hairs were stretched, dried, and baked at ratios 20%, 40%, 60%, 80% and 100%.
  
  
  RESULTS
  The analysis of the amide I band indicated that the transformation from α-helix to β-pleated structure occurred during the stretching process, which could be verified from the tensile analysis. The cysteine oxide in S-O vibration area exhibited that stretching led to the breakage of the disulfide bonds. When the stretching ratio of Caucasian hair was more than a certain ratio, the fiber macromolecular structure was destroyed because Caucasian hair had finer diameter and less medulla than Asian hair. The β turn was easier to retract compared with other conformations, resulted in the content increase. The density measurements revealed that the structure of Caucasian hair was indeed more destroyed than that of Asian hair. The cuticles characterization indicated the length of scales was stretched longer and the thickness became thinner. Caucasian hair tended to collapse to form small fragments at the early stage of stretching. With the increase in stretching ratio, the scales of Caucasian hair lifted up, then flaked off and the scale interval increased accordingly. Asian hair was more easily peeled off than Caucasian hair cuticles with the increase in stretching ratio.
  
  
  CONCLUSIONS
  The secondary structure of Caucasian hair was destroyed more easily than that of Asian hair.
authors: Shanghai Key Laboratory of Advanced Micro & Nano Textile Materials, College of Textiles, Donghua University, Shanghai, China.
authors: A J
authors: AJ
authors: Zhou
authors: H L
authors: HL
authors: Liu
authors: Z Q
authors: ZQ
authors: Du
mesh_terms: D044466:Asian People; D002681:China; D055119:Elastic Modulus / Q000502:physiology; D006197:Hair / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure*; D006801:Humans; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D044465:White People
chemical_list: D011506:Proteins
keywords: density; fourier transform; human hair; infrared spectrum; secondary structure changes