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Tyrosinase-catalyzed modification of Bombyx mori silk fibroin: Grafting of chitosan under heterogeneous reaction conditions

Paper ID Volume ID Publish Year Pages File Format Full-Text
25752 43596 2006 14 PDF Available
Title
Tyrosinase-catalyzed modification of Bombyx mori silk fibroin: Grafting of chitosan under heterogeneous reaction conditions
Abstract

The capability of mushroom tyrosinase to catalyze the oxidation of tyrosine residues of Bombyx mori silk fibroin was studied under heterogeneous reaction conditions, by using a series of silk substrates differing in surface and bulk morphology and structure, i.e. hydrated and insoluble gels, mechanically generated powder and fibre. Tyrosinase was able to oxidize 10–11% of the tyrosine residues of silk gels. The yield of the reaction was very low for the powder and undetectable for fibres. FT-Raman spectroscopy gave evidence of the oxidation reaction. New bands attributable to vibrations of oxidized tyrosine species (o-quinone) appeared, and the value of the I853/I829 intensity ratio of the tyrosine doublet changed following oxidation of tyrosine. The thermal behaviour of SF substrates was not affected by enzymatic oxidation. o-Quinones formed by tyrosinase onto gels and powder were able to undergo non-enzymatic coupling with chitosan. FT-IR and FT-Raman spectroscopy provided clear evidence of the formation of silk-chitosan bioconjugates under heterogeneous reaction conditions. Chitosan grafting caused a β-sheet → random coil conformational transition of silk fibroin and significant changes in the thermal behaviour. Chitosan grafting did not occur, or occurred at an undetectable level on silk fibres. The results reported in this study show the potential of the enzymatically initiated protein–polysaccharide grafting for the production of a new range of bio-based, environmentally friendly polymers.

Keywords
Bombyx mori silk fibroin; Chitosan; Tyrosinase; FT-IR; FT-Raman; DSC
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Tyrosinase-catalyzed modification of Bombyx mori silk fibroin: Grafting of chitosan under heterogeneous reaction conditions
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 125, Issue 2, 1 September 2006, Pages 281–294
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us