State of the art and challenges
Arguably, most of the cultural heritage objects produced using organic materials have high content of protein residues. The application of proteomics analysis based on high-resolution mass spectrometry (MS) allows accurate and relatively affordable sequencing of any protein residue present in quantities above femtomoles, with no need to pre-define a target. As a consequence it is not only possible to confidently identify the protein complex present in a sample, but also the biological species, and in some cases even the tissue, originally used as the source of the material for the production of ancient objects. Proteomics technology also allows for biochemical characterisation of the damage ancient protein residues accumulate over millennia, providing, a rigorous approach to understand and quantify molecular damage affecting this category of biomolecules in cultural heritage material.
Members of the TEMPERA consortium are amongst the pioneers who first applied MS-based ancient protein sequencing in art and archaeology . Ancient protein sequencing was used (UoL) to identify food residues in archaeological pottery , or to characterise paint binders and the chemical damage affecting them (UoN). More recently, paleoproteomics methods allowed characterisation of proteins in mortars and identification of the species of origin of zooarchaeological remains, prehistoric skin garments (UCPH), or medieval parchment ( UoY). In the last year, UCPH demonstrated the feasibility of identification of protein-based wood adhesives. UoY pioneered the ZooMS technique for identification of animal remains.
Investigation of ancient samples presents specific challenges and requirements. All experimental phases require adjustments specific for cultural heritage material. In particular, only a close interaction and collaboration among museum curators, restorers and analytical scientists can lead to the development of innovative sampling procedures compatible with both analytical and conservation requirements. Most of the MS proteomics methods so far used are not initially designed for proteins heavily affected by extended fragmentation, contamination by environmental factors, and biomolecular damage accumulated over millennia.
The involvement of industrial partners in the TEMPERA network will allow access to their industrial expertise. Private-sector collaborators: Thermo and DEVRO, will benchmark their most advanced technological developments against this category of extremely demanding samples.
The TEMPERA network will allow development of dedicated methodological solutions for paleoproteomics analysis of different categories of cultural heritage materials. It will also allow mutual sharing of expertise and experience among leading paleoproteomics laboratories in Europe, aiming at defining common standard analytical protocols, for uniformed treatment of European cultural heritage material. Ultimately, the TEMPERA network will train the right specialists to operate globally at top level in the field. ESRs’ research projects will cover the most relevant topics concerning application of paleoproteomics to cultural heritage.
Palaeoproteomic Profiling of Conservation Layers on a 14th Century Italian Wall Painting
Meaghan Mackie, Patrick Rüther, Diana Samodova, Fabiana Di Gianvincenzo, Clara Granzotto, David Lyon, David A. Peggie, Helen Howard, Lynne Harrison, Lars Juhl Jensen, Jesper V. Olsen, Enrico Cappellini
Ahead of display, a non‐original layer was observed on the surface of a fragment of a wall painting by Ambrogio Lorenzetti (active 1319, died 1348/9). FTIR analysis suggested proteinaceous content. Mass spectrometry was used to better characterise this layer and revealed two protein components: sheep and cow glue and chicken and duck egg white. Analysis of post‐translational modifications detected several photo‐oxidation products, which suggest that the egg experienced prolonged exposure to UV light and was likely applied long before the glue layer. Additionally, glycation products detected may indicate naturally occurring glycoprotein degradation or reaction with a carbohydrate material such as starch, identified by ATR‐FTIR in a cross‐section of a sample taken from the painting. Palaeoproteomics is shown to provide detailed characterisation of organic layers associated with mural paintings and therefore aids reconstruction of the conservation history of these objects.
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