Fibroin degradation – Critical evaluation of conventional analytical methods

Secondary structure transformation and mechanical properties of silk fibers by ultraviolet irradiation and water

“…UV irradiation is a major detriment to archaeological silks on exhibition and it is important to investigate the photo-degradation regarding the conservation of silk cultural relics. 7,18–21 Accelerated light ageing is often used in investigating the properties of materials, which leads to silk yellowing and the decrease of fiber strength due to the photochemical reaction and the generation of free radicals. 22 Fourier transform infrared spectroscopy (FTIR) spectra has been previously used to investigate the nature of sericin and fibroin, characterizing the surface functionalities and the transformation of secondary structures.…”

Evaluating the impact of different exogenous factors on silk textiles deterioration with use of size exclusion chromatography

“…The greatest drop in molecular mass is observed for the samples aged at relative humidity of 70 %, where overall deterioration is powered by high water concentration. In fact, acidic VOCs like acetic acid clearly contribute to acid hydrolysis of polypeptide chain [24]. However, regardless of the level of relative humidity, the final degradation stage of fibroin seems to be similar which may indicate that during ageing the recrystallisation also takes place which inhibits further degradation [18,19].…”

“…Light, temperature and humidity have a detrimental impact on the rate of the degradation, manifested by, for example, glass transition [13], recrystallisation [14,15], oxidative [16][17][18][19] and photooxidative [20,21] changes, and photoinduced -S-S-bond breakdown [22,23]. Additionally, the material during natural ageing emits volatile organic compounds (VOCs), which results in mass loss [24]. VOCs like acetic acid may also contribute to acidic hydrolysis [24].…”

“…Additionally, the material during natural ageing emits volatile organic compounds (VOCs), which results in mass loss [24]. VOCs like acetic acid may also contribute to acidic hydrolysis [24]. The oxidation reactions were examined broadly by Shao et al [25], who presented results of investigations on changes in the crystallinity of fibroin as a function of the compactness of tyrosine, studied through ATR-FTIR and FT-Raman spectroscopies.…”

“…It also enhances the formation of oxygen free radicals [27,28], which attack the most reactive amino acids: tryptophan, tyrosine and phenylalanine in amorphous regions [23,29]. This eventually gives rise to the loss of silk brightness [19,24,30]. Oxidative changes in functional groups of fibroin chains lead to their spatial rearrangement within amorphous regions [14,18], which together with water vapour, VOCs, oxygen or other agents facilitate chain scission.…”