Enzyme-mediated Crosslinking of Wool. Part I: Transglutaminase

Abstract

Felting shrinkage of wool fabric can be controlled by oxidation and protease treatment, however, strength loss usually results. The Agricultural Research Service (ARS) process, providing bleaching, biopolishing, and shrinkage control by peroxycarboximidic acid oxidation and selective enzyme digestion of wool's scales can cause 10 to 18% strength loss. After ARS processing 3 to 5% fabric strength was regained with application of transglutaminase (TG). The TG reactivity involves the transferase-mediated, acyltransfer reaction between glutamine and lysine with the formation of carboxylamide groups of peptide-bound glutamine in wool keratin. Changes in the specular reflectance Fourier transform infrared spectra of the amide I and II regions attributed to the functional groups involved in the transamidation reaction provided evidence that cross-linking through TG had occurred in the fabrics. Optical and fluorescence microscopy showed no influence of TG on the anionic charge imparted by peroxycarboximidic acid oxidation and no influence of TG on the scale smoothing or removal of the enzymatic digestion involved in the ARS process. Confocal microscopy revealed the abundant presence of amine groups in the TG-treated fibers. Thus there is evidence that ARS-processed keratin substrates in the solid state can be self-cross-linked and that they have potential for further reactivity.