Structure and stable isotope ratios of ancient and artificially aged silk fabrics

Study on the photodegradation behaviors of thermal-aged silk

“…Figure 3 depicted FTIR spectra of the silk samples with varying degrees of photoaging within the range of 400 to 4000 cm −1 . The primary regions associated with the amid I (1600-1700 cm −1 ), the amid II (1500-1600 cm −1 ) and the amid III (1190-1300 cm −1 ) are important for assess the structural transformation of silk [12,25]. The characteristic absorption bands of the silk samples are provided in Table N-H bending vibrations, random coil/α-helix), respectively.…”

“…4a and b, the contents of random coil conformation slightly increased while the contents of β-sheet conformation showed a minor decrease with extending the exposure time. It is speculated that the experimental lighting conditions can induce the change of the secondary structure of silk, where light would break the bonding between the hydrogen bonds and result in the cleavage and reorganization of polypeptide chains [25]. Since β-sheet conformation and random coil conformation are mainly distributed in the crystalline region and the amorphous region respectively, the crystalline region is gradually destroyed upon photoaging leading to the conversion of β-sheet conformation to random coil conformation, and an increase in the content of random coil conformation in the amorphous region.…”

“…Tan and Dang reviewed researches on light influence of highly sensitive artworks and indicated color change is one aspect of degradation, while the mechanism of lighting deterioration in regard to the changes of chemical composition and molecular structure is necessary to be studied by employing accelerated photoaging experiments [13]. And in line with the points, UV-induced degradation of silk was studied to evaluate the secondary structure transformation [23,24], changes of structure and isotope ratios [25], and color and structure variation [12]. It can be seen from previous research that the discoloration of light-sensitive artifacts under various light sources has been widely studied since color change is commonly an obvious sign of light ageing.…”