Thermal Aging Degradation Mechanism Of Silk Fabric Based On Proteomics

Silk,a great invention of ancient China,is an important part of Chinese historical culture,and a bridge between East and West.Chinese ancestors produced exquisite silk by sericulture,reeling,spinning and weaving.However,silk fabrics are highly susceptible to aging and degradation during the long-term burial process.With the development of archaeology,more and more ancient silk remains have been found in archaeological sites in China and other countries.The origin of silk and the protection of unearthed silk have become the focus of research.Therefore,it is of great significance to study the changes of protein components and the degradation mechanism in the whole silk relics life cycle,for exploring the origin of silk and the protection of unearthed silk.In this thesis,high-throughput proteomics was used to detect protein and specific polypeptide in three key stages of the life cycle of silk relics,and the proteins most likely to accompany silk relics were screened.Subsequently,a silk protein structure research system based on unlimited degradation proteomics was established for these key proteins,and the thermal aging degradation mechanism of silk was analyzed from both the macro and micro levels by combining mechanical properties,secondary structure and molecular weight characterization.1)Various protein components of silkworm cocoons,modern silk and silk relics were analyzed by proteomics.During the process from silkworm cocoon to silk,only one of the three sericin remained during degumming and a variety of functional proteins were also removed.Vast majority of the proteins were completely degraded during the long degradation process,while the heavy,light and glycoprotein chains of silk protein were partially degraded,and the light chain degradation rate was the slowest.Fifteen common peptides and five common proteins were identified in silkworm cocoons,modern silk and silk relics,of which the two highest abundant peptide sequences are expected to molecular markers for silk detection,and three silk fibroin proteins can be used as key proteins to study the mechanism of silk deterioration.2)A strategy combining unlimited degradation with mass spectrometry-based proteomics technique,was proposed which was used to understands protein breakage propensity and secondary structure changes by detecting changes in the content of specific peptide groups in complex proteomes.Peptide sequences which composed β-sheet in the silk fibroin heavy chain are degraded at the early stage of aging.Crystalline region slowed down the occurrence of bond breaking,and the fragmented crystal region could accelerate the degradation of the crystal area.Combined with mechanics property and crystallographic characterizations,a model of thermal aging degradation mechanism was proposed.The degradation of heat-aging silk was essentially the reduction of the number of connection molecules between/in β-sheets and β-strand crystals,as well as the defects of the crystal nucleus itself,which had little to do with the crystallinity.