Decai Gong

Biomolecular Evidence of Silk from 8,500 Years Ago

Pottery, bone implements, and stone tools are routinely found at Neolithic sites. However, the integrity of textiles or silk is susceptible to degradation, and it is therefore very difficult for such materials to be preserved for 8,000 years. Although previous studies have provided important evidence of the emergence of weaving skills and tools, such as figuline spinning wheels and osseous lamellas with traces of filament winding, there is a lack of direct evidence proving the existence of silk. In this paper, we explored evidence of prehistoric silk fibroin through the analysis of soil samples collected from three tombs at the Neolithic site of Jiahu. Mass spectrometry was employed and integrated with proteomics to characterize the key peptides of silk fibroin. The direct biomolecular evidence reported here showed the existence of prehistoric silk fibroin, which was found in 8,500-year-old tombs. Rough weaving tools and bone needles were also excavated, indicating the possibility that the Jiahu residents may possess the basic weaving and sewing skills in making textile. This finding may advance the study of the history of silk, and the civilization of the Neolithic Age.

Transglutaminase-mediated restoration of historic silk and its ageing resistance

IntroductionTransglutaminase-mediated polymerization, unlike the traditional restoration methods based on the application of synthetic polymers, has proved to be a potential strategy in the restoration of historic silk. In the present study, the treatment process has been adapted to satisfy the needs of consolidating historic silk fabrics in various cases. Artificially aged (dry thermal ageing) silk samples were restored using this method. The effects of the reaction on silk fibers were investigated by tensile tests, colour difference tests, scanning electron microscopy and FT-IR. The ageing resistance of the restored samples was evaluated.ResultsThe results showed that tensile strength, elongation rate at breakage and micro morphology of the silk samples were remarkably improved without significant colour difference after restoration. FT-IR spectroscopy confirmed the existence of transglutaminase-induced biopolymers in the restored silk samples and demonstrated that the transglutaminase-mediated restoration did not change the basic structure of silk protein. The ageing resistance of the restored samples evaluated using standard methods ensured that the treatment would not introduce any long term problems. The method was then applied to genuine historic silk fabrics and achieved the desired results.ConclusionsFrom the results of this study, the effectiveness of transglutaminase-mediated polymerisation to restore historic silk was demonstrated.

Micro-mechanism elucidation of the effects of dehydration on waterlogged historic silk (Bombyx mori) by near-infrared spectroscopy

Abstract It is widely accepted experience among archaeologists that the mechanical properties of waterlogged historic silk artifacts will be improved to some extent after the gradual evaporation of water. For the purpose of understanding the micro-mechanism of this interesting phenomenon, near-infrared spectroscopy was applied to study the microstructure of historic silk fibers before and after the transition from a water-saturated to dry state. It is demonstrated that the interaction of water with silk varies significantly depending on the condition of the material. The change of moisture content can induce rearrangement of hydrogen bonds and conformation transition in silk fibers, thus altering their mechanical properties. Our results vindicate the practical observation that by exploiting the dehydration effects, fragile water-saturated silk artifacts in archaeological sites can successfully be extracted and transported to conservation laboratories with reduced risk of damage.

Different Types of Peptide Detected by Mass Spectrometry among Fresh Silk and Archaeological Silk Remains for Distinguishing Modern Contamination

Archaeological silk provides abundant information for studying ancient technologies and cultures. However, due to the spontaneous degradation and the damages from burial conditions, most ancient silk fibers which suffered the damages for thousands of years were turned into invisible molecular residues. For the obtained rare samples, extra care needs to be taken to accurately identify the genuine archaeological silk remains from modern contaminations. Although mass spectrometry (MS) is a powerful tool for identifying and analyzing the ancient protein residues, the traditional approach could not directly determine the dating and contamination of each sample. In this paper, a series of samples with a broad range of ages were tested by MS to find an effective and innovative approach to determine whether modern contamination exists, in order to verify the authenticity and reliability of the ancient samples. The new findings highlighted that the detected peptide types of the fibroin light chain can indicate the degradation levels of silk samples and help to distinguish contamination from ancient silk remains.

A potential scavenger of carbon radicals for ancient carbonized silk fabrics: Superoxide Dismutase (SOD)

Superoxide Dismutase (SOD) was proposed as a potential scavenger of carbon radicals in ancient carbonized silk fabrics. Ancient and artificially carbonized silk samples were treated using this method. The optimal experimental conditions of the treatment were determined by variance analysis. The effects of the scavenging on carbonized silks were investigated by electron paramagnetic resonance (EPR). The results showed that the carbon radicals in both ancient and artificially carbonized silks were cleared to a great extent. The ageing resistance of the treated samples and scanning electron microscope (SEM) images of samples before and after treatment ensured that the treatment would not aggravate the deterioration of silk. Thus, the potential of SOD to scavenge carbon radicals in historic silk was demonstrated. Our research may help to alleviate further degradation which could occur during preservation of silk.