Ilaria Bonaduce

Changes and degradation phenomena of proteins in Cultural Heritage objects.

Ilaria Bonaduce; Sibilla Orsini; Maria Perla Colombini; Anna Lluveras-Tenorio

Dipartimento di Chimica e Chimica Industriale, Universitá di Pisa, via Moruzzi 13, 56124 Pisa, Italy

Many analytical methods for the identification and characterization of proteins in samples from cultural heritage, such as paintings and works-of-arts, archaeological and paleontological findings have been presented in the literature, based on staining, immunological, spectroscopic, chromatographic, and proteomics techniques (1). Each of these techniques has shown the potential of being able to successfully detect, and in some cases, identify, proteins in selected samples, but all of them present more or less drawbacks, which are seldom discussed and rarely put in relation to degradation mechanisms. In the course of ageing, though, proteins are subject to significant changes, including amino acids modifications (such as deamidation, hydroxylation and oxidation) and structural modifications, which are not all well understood.

This paper presents our research aimed at improving our understanding of changes and degradation phenomena taking place in proteins present in artistic and archaeological objects. The research is based on the use of analytical pyrolysis - evolved gas analysis coupled with mass spectrometry (EGA/MS), pyrolysis coupled with gas chromatography/mass spectrometry (Py/GC/MS), double shot pyrolysis gas chromatography/mass spectrometry (DSP/GC/MS) - in combination with gas chromatography/mass spectrometry (GC/MS), bottom-up proteomics based on tandem mass spectrometric analysis of peptide solutions obtained with non-enzymatic proteolytic digestion, and spectroscopic techniques, including FTIR and XPS.

Results show that hydrolysis, formation of intermolecular aggregates stabilised by weak hydrophobic and hydrogen bonds, covalent cross-linking and formation of strong complexes with cations are main pathways of degradation that may be encountered in paint layers and archaeological residues containing proteins.

References:

(1) Dallongeville, S.; Garnier, N.; Rolando, C.; Tokarski, C. Chemical Reviews 2016, 116, 2-79.