Development of\na Combined Protein and Dye Extraction\nApproach for the Analysis of Keratin-Based Textiles

Archaeological textiles\nrepresent precious remains from ancient\nculture; this is because of the historical and cultural importance\nof the information that can be obtained by such relics. However, the\nextremely complicated state of preservation of these textiles, which\ncan be charred, partially or totally mineralized, with heavy soil\nor biological contamination, requires highly specialized and sensitive\nanalytical tools to perform a comprehensive study. Starting from these\nconsiderations, the paper presents a combined workflow that provides\nthe extraction of dyes and keratins and keratin-associated proteins\nin a single step, minimizing sampling while maximizing the amount\nof information gained. In the first phase, different approaches were\ntested and two different protocols were found suitable for the purpose\nof the unique workflow for dyes/keratin-proteins: a slightly modified\nurea protocol and a recently proposed new TCEP/CAA procedure. In the\nsecond step, after the extraction, different methods of cleanup and\nworkflow for proteins and dyes were investigated to develop protocols\nthat did not result in a loss of aliquots of the analytes of interest\nand to maximize the recovery of both components from the extracting\nsolution. These protocols investigated the application of two types\nof paramagnetic beads, unmodified and carboxylate-coated hydrophilic\nmagnetic beads, and dialysis and stage-tip protocols. The newly designed\nprotocols have been applied to cochineal, weld, orchil, kermes, and\nindigo keratin-based dyed samples to evaluate the effectiveness of\nthe protocols on several dye sources. These protocols, based on a\nsingle extraction step, show the possibility of investigating dyes\nand keratins from a unique sample of 1 mg or lesser, with respect\nto the thresholds of sensitivity and accuracy required in the study\nof textile artifacts of historical and artistic values.