Analytical Sciences

Application of Electron Paramagnetic Resonance and Solid-state ¹³C Nuclear Magnetic Resonance of Cross-polarization/Magic Angle Spinning to Study Enzymatic Degradation of Silk Fabrics

Yuan ZENG,*1,*2 Zhiqin PENG,*1,*2 Bing WANG,*1,*2 Zhiwen HU,*1,*2 Junmin WAN, *1,*2 and Yang ZHOU*3,*4

*1 Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, P. R. China
*2 Institute of Textile Conservation, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, P. R. China
*3 China National Silk Museum, Hangzhou, Zhejiang 310002, P. R. China
*4 Key Scientific Research Base of Textile Conservation, State Administration for Cultural Heritage, Hangzhou, Zhejiang 310002, P. R. China

The enzymatic degradation of silk by protease XIV has been investigated by using scanning electron microscopy (SEM), Fourier transfer infrared spectroscopy (FTIR), solid-state ¹³C nuclear magnetic resonance of cross-polarization/magic angle spinning (¹³C CP/MAS solid state NMR) and electron paramagnetic resonance (EPR). Micro-morphology of protease XIV aged samples showed that microfilaments were stripped out from the surface of silk fibers. The results of FTIR and ¹³C CP/MAS solid-state NMR indicated that the enzymatic degradation process could be divided into two stages. The EPR spectra indicated that the enzymatic degradation process was related to the free radical with the g-factor value of 2.0043. We also proposed that at the first degradation stage, the free radicals were apt to lose activities due to the loose structure of the non-crystalline region; at the second degradation stage, the free radicals produced in the crystalline region tended to be stored.

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