The Identification And Analysis Of The Silk Residues In The Tomb Soils From Jiahu Site

As an important invention of the Chinese civilization, silk and its culture, technology, social connotation provide a lot of important research materials for various discipline, including archaeology, history, historiography of science and technology etc.The unearthed silk fragments indicate that the origin of silk should be no later than5500years ago. However, it must need a long period to develop silk weaving technology from the discovery of silk fibers to make them into silk textiles. Therefore, the use of silk fibers are probably much earlier than5500years ago. The materials of silk textiles are silk fibers, and their intact shape are hardly preserved after a long burial period, which bring great obstacles to explore the origin and development of early silk. How to explore earlier evidence for studyong earlier use of silk became important issues when the macroscopic morphology of most silk textiles are disappeared.With respect to the silk fabrics, the invisible silk protein residue easier to survive. I may be a kind of new evidence to explore the early silk. The research objects of this study are the potential silk protein residues in ancient ruins. There are two main comments in this paper:to build the extraction and identification methods for ancient silk protein residues and to detect the silk pretein residues in the tomb soils from the Jiahu Site.The establishment of extraction and identification method is the base for this study.The biological mass spectrometry and bioinformatics analysis are the basic research methods. Start with fresh silk, the basic experimental procedure for the extraction and identification of silk protein residue were developed:Obtaining silk fibroin solution with calcium-alcohol solution——Desalinating and concentrating the silk fibroin solution with dialysis and ultrafiltration——digesting fibroin with chymotrypsin——Detecting peptides by LC-MS——Obtaining amino acid sequence of each peptide after database search——determining the existence of silk protein residues in samples Then, the Yinan Qing clothing fragments, Lu’an Warring States Huangwei fragments and the Hengshui Zhou dynasty soil sample with Huangwei imprint were carried out by established method. The detection of silk protein in these three samples seggut that biological mass spectrometry can be used to analyze the ancient silk residues. Further analysis showed that there are some differences in the experimental results between ancient samples and fresh silk. The main aspects are:the solubility’s decline of ancient silk and the decreace of detected peptide types of ancient silk protein.The solubility decline is closely linked to the degradation of the ancient silk proteins: serious degradation lost a great deal of component the amorphous regions, weakened the swelling of silk fibroin, and increased the reaction difficulty on silk crystalline regions by alcohol-calcium solution. Finally, the solubility of ancient silk protein decline gradually. Compared with the fresh silk, the ancient samples generally require a longer time to increase dissolved amount of fibroin. Furthermore, in order to ensure the alcohol-calcium solution can contact with the silk protein resides in the soils, the soil samples should be ground into powders before extraction. Meanwhile, in order to improve the accuracy of the results, each detected petides should be examined by addionan manual.The decreace of detected peptide types of ancient silk protein can help to determine the existence of contamination in ancient samples. The the aggravation of ancient silk protein’s degradation gradually reduced the peptide types detected in ancient samples. Among them, the peptides’decline of the light chain subunit in fibroin is most obvious and no peptides of light chain were detected in Lu’an Warring States Huangwei fragments and the Hengshui Zhou dynasty soil samples with Huangwei imprint. Therefore, the detected peptide results of the light chain can be used as an important indicator for determining the contamination:if no peptide of the light chain were detected in the ancient samples silk, it means that the samples were not contaminated and silk proteins in samples were severely degraded; on the contrary, if rich peptides of the light chain were detected in samples, it means that the contamination may mixed in the samples or the silk protein were in a good preservation status. The establishment of this method makes the biological mass spectrometry can determine the contamination without other techniques.In order to explore earlier silk evidence, an age-old civilization and a relatively well-developed archeaological site is essential. With many top findings of the world, Jiahu site is one of the best choices.Located in central region of Henan Province in China, a large number of textile or sewing tools, including needles, bone awl, pottery spinning wheels, wrapped wire bone plates were unearthed which indicate primitive weaving skills were mastered by Jiahu residents in that time. However, no textile fibers presvered makes it difficult to determine whether the silk were used by fibrous morphology observation. If the silk fibers started to be used, they has great opptunities to be buried in tombs and their degradation residues may preserved and be identified today. In this study, the special peptides of silk fibrion were detected in the Tomb M436and M451of Jiahu site via liquid chromatography-mass spectrometry technology. No silk peptides detected in the raw soils suggest that the silk protein residues were unique found in the tombs and should come from the funerary objects. Therefore, Jiahu ancestors probably already started to use silk fibers, and to weave the fibers into silk textiles. With these fingdings, it can inferred that the earliest use of silk inferred should not be later than8500years ago,and Jiahu may be the cradle of sericulture and silk manufacturing.