• proteomic analysis
• paintings
• degraded proteins
• mass spectrometry

Proteins are the building blocks of cells in all living species, and they carry the information necessary for life, replication, defence and reproduction. It has recently been proven that proteins are much longer preserved than DNA, as they have been found in paleontological findings dating back to the Pleistocene. Proteins are also important components of archaeological findings, including bones, textiles and residue of ceramic and vessels, and they are the ingredients of cosmetics thanks to their ability to protect the first layer of the skin from the harsh effects of aging and environment (such as UV rays, pollution and free radicals). Proteins are also fundamental constituents of works-of-art, used as paint binders, as adhesives and varnishes in painting, polychromies and to decorative objects. The study of proteins in artistic, archaeological and paleontological objects provides significant information to understand the evolution of life through the ages, to improve our knowledge of our history, to understand technological developments and artistic manufacture, and to bring essential information to art-historians and conservators.

This PhD thesis aims at studying structural and molecular changes undergone by proteins and proteinaceous materials commonly used in paintings, polychromes and archaeological objects, as an effect of manufacture and ageing. This information is fundamental to design reliable analytical techniques, approaches, methods and models for data analysis, to successfully characterise and indentify proteins in art and archaeological objects. Many analytical methods for the identification and characterization of proteins from artistic, archaeological and paleontological objects have been proposed . Although, procedures optimized for protein denaturation and extraction from ancient materials and artworks were recently developed, the analysis of these samples present several drawbacks and the identification of protein is often a difficult task. As an effect of the long term exposure to the changeable and sometimes harsh environments where the object is displayed or stored, degradation phenomena take place. Besides some information are available on the degradation of certain acids -deamidation, hydroxylation, oxidation and carbonylation - very little is known on the degradation of proteins in art and archaeological objects. The main observation relates to the loss of solubility of aged proteins, which has been suggested to be related to aggregation, crosslinking and complexation phenomena with pigments. If these hypothesis prove to be true, then they might account for several drawbacks that are encountered in the analysis of proteins in degraded samples. Aggregation, crosslinking and complexation with pigment may make the protein binding site unavailable for the stain, may control the degree of flexibility of the polypeptides chains, and may form deleterious changes of the protein conformation, compromising the antigen/antibody interaction, cause loss of solubility, making the protein extraction necessary for chromatographic and mass spectrometric techniques a difficult task and may affect the degree of access of cleavage enzymes in proteomics experiments.