Structure modifications induced in silk fibroin by enzymatic treatments. A Raman study

Following oxidation with mushroom tyrosinase, the tyrosine bands of Bombyx mori fibroin decreased in intensity but did not disappear. The increase of the I853/I829 intensity ratio indicated that the Tyr residues not accessible to the enzyme were located in a strongly hydrophobic environment. Raman spectroscopy provided evidence that chitosan was effectively grafted onto oxidized silk, probably via the Schiff-base mechanism, as shown by the behavior of the imine band at about 1646 cm−1. Grafting chitosan onto silk fibroin resulted in a β-sheet→random coil conformational transition of the protein component in the bioconjugated product.