关键词: 丝绸, 降解机理, X射线衍射, 二级结构, 蛋白质组学

Abstract: Silk cultural relics, with their historical, cultural, and artistic value, offer invaluable insights into ancient civilizations. However, like all natural materials, silk is highly susceptible to physical, chemical and biological factors, losing its original value. Therefore, the preservation and restoration of silk cultural relics have always been the focus of cultural relic protection, and in-depth research on the microbial degradation process of silk fibers is of great importance to formulate effective strategies for the protection. The complex multi-level structure of silk fibroin leads to its complicated degradation mechanism, changes in each level of structure may lead to the degradation of silk. And the changeable environment also brings difficulties to the research of aging and degradation of silk cultural relics. The scarcity and non-renewability of silk cultural relics are also major challenges for cultural relics conservationists. To overcome these difficulties, the artificial simulation aging method can be used to study the aging and degradation behavior of silk fibroin.
To reveal the microbial degradation mechanism of silk, this paper investigated the macroscopic and microscopic structural changes of silk before and after degradation of Aspergillus oryzae metabolites using proteomics combined with thermal field emission scanning electron microscopy and XRD techniques. The results of morphological analysis showed that the color of silk changed significantly after aging, and a large number of fibres's shedding and axial cracks appeared on the surface of silk fibres. The results of secondary structure analysis showed that the molecular conformation of silk proteins was damaged, and the degree of crystallinity was significantly decreased. The proteomics results showed that both the number of polypeptides and the total abundance of proteins in silk fibroin decreased significantly, indicating that silk fibroin can be degraded by metabolites, and the abundance of heavy chains constituting the crystalline region of silk fibroin decreased the fastest.
A model of deterioration of silk fibroin by Aspergillus oryzae is postulated: Aspergillus oryzae focuses on the decomposition of fibroin heavy chain through degradation, and the structure of the crystalline region of the silk fibroin collapses into a loose amorphous structure, and the silk loses its original physicochemical properties, and is eventually completely degraded and destroyed. This study is of great significance for the in-depth understanding of the deterioration mechanism of ancient silk and provides an important basis for the targeted protection and restoration strategies for silk cultural relics.

Key words: silk, degradation mechanism, XRD, secondary structure, proteomics