Abstract
Silk artifacts constitute an invaluable heritage, and to preserve such patrimony it is necessary to correlate the degradation of silk fibroin with the presence of dyes, pollutants, manufacturing techniques, etc. Fourier Transform Infrared Spectroscopy with a Focal plane array detector (FPA FTIR) provides structural information at the micron scale. We characterized the distribution of secondary structures in silk fibers for a large set of South American historical textiles, coupling FTIR with multivariate statistical analysis to correlate the protein structure with the age of the samples and the presence of dyes. We found that the pressure applied during attenuated total reflectance (ATR) measurements might induce structural changes in the fibers, producing similar spectra for pristine and aged samples. Reflectance spectra were thus used for the rigorous characterization of secondary structures. Some correlation was highlighted between the age of the samples (spanning over five centuries) and specific changes in their secondary structure. A correlation was found between the color of the samples and structural alterations, in agreement with the chemical nature of the dyes. Overall, we demonstrated the efficacy of reflectance FPA µ-FTIR, combined with multivariate analysis, for the rigorous and non-invasive description of protein secondary structures on large sets of samples.
Highlights
The term “silk” is generally used to indicate the product of the transformation of domesticated Bombyx mori cocoon’s spun fiber after the degumming process
Many authors elected attenuated total reflectance (ATR) as the standard technique for the investigation of textiles, including silk. This method has highlighted remarkable changes in the secondary structure of fibroin films induced by solvents or thermal treatment[27]; Belton et al have shown the utility of ATR spectra fitting to elucidate the conformational make up of silk protein in self-regenerated silk films[28]; in the case of naturally or artificially aged silk textiles, ATR analysis showed less evident changes in the secondary structure of aged fibroin compared to pristine silk
A large set of historical and pristine silk samples was analyzed through Focal Plane Array (FPA) μ-Fourier Transform Infrared Spectroscopy (FTIR), comparing the information obtained from ATR and reflectance measurements
Summary
The term “silk” is generally used to indicate the product of the transformation of domesticated Bombyx mori cocoon’s spun fiber after the degumming process (i.e. a chemical treatment that removes the coating of sericin protein from the fiber[1]). No pattern was observed linking the age (or color) of the samples with the progress of the degradation process To fill this gap, in this work we investigated the correlation of the protein structure of a large set of historical silk samples with their age, and with the presence of dyes. FPA μ-FTIR was carried out on samples of historical flags and banners of different origins, obtained from the textile collection of the National Museum of Colombia, where the objects were kept in the last 200 years under identical conditions (in terms of light, relative humidity, temperature, etc.) and did not undergo any restoration intervention. Principal components analysis (PCA) was performed to correlate the different structures with the age and color of the samples
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
