| 1. |
- Solazzo, Caroline, et al.
(author)
-
Application of redox proteomics to the study of oxidative degradation products in archaeological wool
- 2015
-
In: Journal of Cultural Heritage. - : Elsevier BV. - 1296-2074 .- 1778-3674. ; 16:6, s. 896-903
-
Journal article (peer-reviewed)abstract
- Most archaeological and historical textiles (clothing, tapestries, blankets, carpets, etc.) present traces of UV-induced damage when exposed to light during their lifetime. Yellowing of the fibres, fading of the dyes and loss of physical properties, such as tensile strength are the typical indicators of photodegradation. Natural fibres made of proteins, such as wool and silk are particularly sensitive to UV damage. Photo-oxidative damage is caused by the accumulation of chemical modification at the amino acid residue level that lead to a range of oxidation products, including chromophores responsible for changes in coloration, as well as to the breaking of peptide bonds in the protein backbone. Amino acid residues with aromatic side-chain groups are particularly sensitive to photo-oxidation and breakthroughs have been made in recent years in the field of protein science to identify the photoproducts and locate them within proteins. This study explores new methodologies using redox proteomics-based strategies to assess the extent of photodamage in ancient wool textiles, by identifying modifications occurring at the molecular level. Using a scoring system to determine the level of oxidation in amino acids with aromatic side-chains (tryptophan, tyrosine, histidine and phenylalanine), we compare the effects of dyes and mordants on fibres after UV ageing, and assess the extent of oxidation on the different proteins composing the wool fibres. We determine that dyes and mordants have the capability of slowing down photo-oxidation during ageing. We also assess the effect of UV irradiation on deamidation, a modification targeting glutamine and asparagine, as it is a common marker of ageing in ancient proteins.
|
|
| 2. |
- Solazzo, Caroline, et al.
(author)
-
Modeling deamidation in sheep α-keratin peptides and application to archaeological wool textiles
- 2014
-
In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 86:1, s. 567-575
-
Journal article (peer-reviewed)abstract
- Deamidation of glutamine (Q) and asparagine (N) has been recognized as a marker of degradation and aging in ancient proteins. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) to study deamidation in wool textiles, we identified eight peptides from α-keratin proteins in sheep wool that could potentially be used to assess the level of degradation. For each chosen peptide, the extent of deamidation was determined by comparing the calculated theoretical distribution with the measured distribution using a genetic algorithm that gives the best fit to the measured distribution. Variations in the levels of deamidation were observed between peptides and in modern wool samples buried for up to 8 years in which deamidation levels were relatively low under short-term burial. In contrast, deamidation was higher in archeological textile fragments from medieval sites ranging from the 9th to 13th century in York (United Kingdom) and Newcastle (United Kingdom) and from the 13th to 16th century in Reykholt (Iceland). Major differences were observed between the British and the Icelandic samples, showing a negative correlation between age of samples and levels of deamidation, but highlighting the effect of local environment. In addition, nanoscale liquid chromatography–electrospray ionization tandem mass spectrometry (nanoLC–ESI-MS/MS) data indicated that deamidation in wool’s α-keratin was influenced by primary and higher-order structures. Predominance of deamidation on glutamine rather than asparagine in the archeological samples was attributed to a higher abundance of Q in the α-helical core domain of keratins, neighboring residues and steric hindrance preventing deamidation of N.
|
|
