Analysis of lecithin treatment effects on the structural transformation of wool fiber using vibrational spectroscopy

The keratin macromolecule in wool fiber may be found in α-helix or β-sheet conformations besides a disordered portion. The physical and chemical treatments may cause transformations between α-helix and β-sheet conformations. The aim of this study was to investigate the influence of lecithin treatment on the wool fiber using the micro-Raman spectroscopy and Fourier transform infrared spectroscopy. Characteristic bands found in the FTIR spectra of wool fibers including the amide A, amide B and amide I-III, which are assigned to the peptide bonds of wool keratin and arise from the amide bonds that link the amino acids. The lecithin treatment didn't affect the peak position of amide bands and only slightly influenced their intensity. It means that the lecithin treatment didn't change the chemical structure of wool fibers. The amide I and III regions, CC skeletal vibration region, and SS bonds vibration regions were analyzed with the Raman microscope. The results indicated the peak area of α-conformation increased gradually by lecithin treatment of the wool fiber, while the peak area of β-conformation decreased. Therefore, it seems that lecithin treatment of the wool fiber resulted in transformation of β-sheet to α-helix.