Buyid Silk and the Tale of Bibi Shahrbanu: Identification of Biomarkers of Artificial Aging (Forgery) of Silk

摘要

src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2017/ancham.2017.89.issue-19/acs.analchem.7b02854/20170927/images/medium/ac-2017-028548_0006.gif">Buyid silk forgery is one of the most famous silk forgeries in the world. In 1924–1925, excavation of the Bibi Shahrbanu site in Iran unearthed several silk textiles. The silks were thought to be of the Buyid period (934–1062 BCE) of the Persian Empire and have since been known as the “Buyid silks”. In the 1930s, more silk appeared and was reported as being from the Buyid period as well. Controversy over the authenticity of these silks escalated after the purchase of the silks by museums throughout the world. Extensive investigations of several of these silks have been conducted over the years with respect to iconography, weaving patterns, dyes/mordant, style, and even radiocarbon dating. It was found that most of the silks are not from Buyid period. To test the authenticity of these silk fabrics, the recently developed silk dating technique using amino acid racemization (AAR) in conjunction with capillary electrophoresis mass spectrometry was applied to 13 Buyid silk specimens from the Textile Museum collections. Among these silk specimens, the AAR ratios of only one specimen were consistent with authentic silk fabrics collected from various museums. In addition, the aspartic acid racemization ratio of this specimen was also consistent with its 14C dating. The other “Buyid silks” showed excessive levels of amino acid racemization not only for aspartic acid, but also for phenylalanine and tyrosine, inconsistent with racemization rates of these amino acids in authentic historical silk fabrics. Treatment of modern silk with a base at different pH and temperature reproduced the AAR pattern of the Buyid silks, implying that chemical treatment with a base at relatively high temperatures was perhaps the method used to artificially age these fabrics. The results imply that the racemization ratios of aspartic acid, phenylalanine, and tyrosine can be used as biomarkers for identification of naturally versus artificially aged silk.