Affinity of protein fibres towards sulfation
Article first published online: 21 SEP 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 44, Issue 2, pages 190–197, February 2013
How to Cite
Taddei, P., Tsukada, M. and Freddi, G. (2013), Affinity of protein fibres towards sulfation. J. Raman Spectrosc., 44: 190–197. doi: 10.1002/jrs.4168
- Issue published online: 24 JAN 2013
- Article first published online: 21 SEP 2012
- Manuscript Revised: 20 JUL 2012
- Manuscript Accepted: 20 JUL 2012
- Manuscript Received: 15 MAY 2012
- Bombyx mori silk fibroin;
- Tussah silk;
- IR spectroscopy;
- Raman spectroscopy;
- mechanical measurements
Wool, Bombyx mori and Antheraea pernyi (Tussah) silk fibres were treated with chlorosulfonic acid in pyridine and investigated by FT-IR and FT-Raman spectroscopies as well as mechanical measurements. The reactivity towards sulfation was found to decrease along the series: wool > Bombyx mori silk fibroin > Tussah silk fibroin, in agreement with weight gain which decreased along the same series. Accordingly, Tussah silk maintained its intrinsic tensile properties essentially unchanged upon the treatment, while for Bombyx mori silk fibroin, the tensile performance decreased sharply especially at longer reaction times. Sulfated wool was characterized by an increased fibre extensibility.
New IR and Raman bands attributable to various vibrations of sulfated groups were detected in sulfated wool and to a lower extent in Bombyx mori silk fibroin fibres; all the fibres underwent conformational rearrangements upon sulfation, independent of the sulfation yield. Wool fibres treated with chlorosulfonic acid in pyridine bound considerable amounts of sulfate mainly through the hydroxyl groups of serine, threonine and tyrosine. Also, tryptophan and basic amino acids were found to participate to the reaction. B. mori silk fibroin fibres appeared to bind a minor amount of sulfate groups mainly trough the hydroxyl groups of Ser.
Weight gain, spectroscopic and mechanical data are discussed in relation to the difference in fibre morphology, structure and crystallinity, as well as to the amount and accessibility of potentially reactive amino acids. Copyright © 2012 John Wiley & Sons, Ltd.