The analysis of Merino wool cuticle and cortical cells by Fourier transform Raman spectroscopy

Wool fibers are comprised of proteins known as alpha-keratins and have a complex morphological structure. The major components of this structure, the cuticle and cortical cells, differ in the conformations of their chains as well as their amino acid compositions. High quality Fourier transform Raman spectra of cortical and cuticle cells isolated from fine Merino wool fibers have been obtained. Raman spectroscopy has been shown to be sensitive to the differences in both secondary structure and amino acid composition. The cortical cells were found to be higher in alpha-helical content as compared to the cuticle cells, which had an increased disordered content. Specific information, consistent with amino acid analysis results, regarding cystine, tyrosine, tryptophan, and phenylalnine residues, were obtained for both the cortical and cuticle cells. In addition, the Raman spectra provided information about free thiol groups, amino acids residues with amide group side chains, and residues with protonated carboxyl group side chains. Middle ir transmission spectra of these isolated cells were also obtained. In comparison to the Raman data, the middle ir spectra were found to be not as rich in information.