The parallel helices of the intermediate filaments of α-keratin

• Published in: International journal of biological macromolecules 2002-04, Vol.30 (2), p.95-96
• Main Authors: Feughelman, M., Lyman, D.J., Willis, B.K.
• Format: Article
• Language: English
• Subjects: Animals; Horses; Intermediate Filaments; Keratins - chemistry; Protein Structure, Secondary; Spectroscopy, Fourier Transform Infrared - methods; α-Helices; α-Keratin
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/S0141-8130(02)00005-3

Recent Fourier transform infrared spectroscopy (FTIR) with attenuated total reflection technique (ATR) has been applied to α-keratin fibers (horse-hair) extended in water both at 21 and 95 °C. Infrared absorption bands in the Amide 1 region indicated that at extensions to 40–50% strain in water at 21 °C α-helices had completely disappeared and parallel β-sheets were formed [Appl. Spectrosc. 55 (2001) 552]. However, when the hair fibers were extended to the same strain at 95 °C in water the result was the formation of anti-parallel β-sheets. These results suggest that the relatively more stable anti-parallel β-state [Polymer 10 (1969) 810] is only attained in extended α-keratin fibers at elevated temperatures and must result from major molecular rearrangement. It was concluded that the α-helices in the intermediate filaments (IFs) of α-keratin fibers must be parallel. This is in contrast to the previously accepted orientation of anti-parallel α-helices, based primarily on findings of X-ray diffraction studies of the structure of β-keratin in highly extended fibers [Polymer 10 (1969) 810; Keratins, IL: Thomas Springfield (1972); Nature 316 (1985) 767].