Abstract

Silk fibers are found in many important historic textiles and artefacts. Raw silk is a proteinaceous fiber consists of two major proteins: The main fibrous component fibroin, and amorphous protein sericin. In commercial use, sericin is normally removed by degumming. Fourier transform infrared (FTIR) spectroscopy is a powerful tool for fiber identification and can provide both qualitative and quantitative information about protein conformations. The amino acid composition of fibroin and sericin significantly differs from each other, thus they can be easily differentiated by IR spectroscopy. In this study some archaeological silk textile specimens, obtained during the excavations in Ancien Ainos (Enez), one of the most important archaeological sites in Turkey together with 150 years old and new Bombyx mori silk textiles were investigated using Attenuated Total Reflectance-Fourier transform infrared (FTIR) spectroscopy. The main aim of our research was to investigate conformational changes of silk protein, caused by ageing depending on the environmental conditions. It was found that structural transformations from β-sheet domain to β-turn and disordered conformations occur due to degradation. By aging, the changes in molecular structure and the formation of oxidative moieties were investigated. The crystallinity and oxidation degrees of the silk fibroin were defined by the investigations of the ratios of integrated intensities of β-Sheet to disordered structure and the integrated intensity ratios of Amide I/Amide II, respectively.

Keywords: Amide bands; Bombyx mori silk; Degradation; IR spectroscopy; Protein secondary structure