Insight of silk relics of mineralized preservation in Maoling Mausoleum using two enzyme-linked immunological methods

Mineralized textiles often unearthed along with metal objects, are textile residues in which the fibers are partially or completely replaced by minerals. Some textile fragments with intact fiber shapes but mineralization on the surface of a ring-shaped iron sword, had recently been found from Maoling Mausoleum in Shanxi province, China. In this study, three-dimension microscope, scanning electron microscope-energy disperse spectroscopy (SEM-EDS) and Raman spectroscopy were used to observe the morphology of fiber and analyze the mineral element information, and two immunology testing techniques would be used to determine whether the textile fragments included the silk protein. The results showed that the hilt string imprint (sample A) was a twill braiding with cinnabar remaining on the surface and the blade textile imprint (sample B) was a tabby fabric, and these fibers were mineralized by iron ions to form a cavity structure. The morphology of sample B was similar to that of mulberry silk with a smooth surface and a triangular cross section. At the same time, silk protein was successfully detected in a few milligrams of sample B using fibroin polyclonal antibody by Enzyme-linked Immunosorbent assay (ELISA) and immunofluorescence method (IFM). Thus, it can be inferred that the iron sword was covered or wrapped in silk at that time. This research provided a technical support for the identification of silk residues in mineralized textiles, which is of great significance for the study of early organic fabrics.