Diana Samodova

MS-based Palaeoproteomic Evaluation of Oxidative Damage in Artistic Objects.

Diana Samodova§, Meaghan E. Mackie§,£, Enrico Cappellini£, Christian D. Kelstrup§, Jesper V. Olsen§

§ University of Copenhagen, Novo Nordisk Foundation Center for Protein Research, Blegdamsvej 3B, 2200 Copenhagen, Denmark; £ Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen, Denmark

Proteins are known to be the main targets for free radicals and other oxidants due to their high abundance in biological systems and reactivity. Free radicals usually cause an extensive damage of the multiple side-chain and backbone sites in proteins, yielding various oxidation products (e.g. carbonyls, commonly used markers of protein damage).

Besides chemical oxidation, UV-mediated oxidation is one of the most frequently-occurring photo-chemical reactions. This type of oxidation produces specific intermediate peroxidic species during photochemical oxidation of chromophoric amino acids - tryptophan (Trp), histidine (His), tyrosine (Tyr), cysteine (Cys), methionine (Met), and phenylalanine (Phe).

Peroxidic species and their tautomeric forms (other di-oxidation products), in their turn, can be considered as marker intermediates distinguishing photo-oxidation from the chemical one. Moreover, these intermediates can be used as markers of UV-related damage, enabling the tracing of photo-induced degradation status and conservation history of artistic objects.

The presence of above mentioned photo-oxidative PTMs in cultural heritage materials can be characterized using tandem mass-spectrometry based proteomics. In the current work this technique has been successfully applied to the study of photo-oxidative damage of a medieval mural painting (Mackie et al., 2018). Remarkably high abundance of His di-oxidation products, compared to the negative control samples, showed that the proteinaceous material had undergone an extensive UV exposure. The obtained results also enabled reconstruction of conservation history of the studied sample revealing the possible sequence of application of the different conservation layers.

Being the first example of photo-oxidative marker PTM application to characterization of cultural heritage materials, we believe that the elaborated methodology has a great potential for further plaeoproteomic applications.