Targeted proteomics for the analysis of cultural heritage: application of broadband collision-induced dissociation mass spectrometry.

A broadband collision-induced dissociation (bbCID) fragmentation mode was proposed for liquid chromatography-mass spectrometric targeted analysis of tryptic peptides obtained from proteins in samples of decoration paint coating. In this approach, a mass spectrometric dataset contains the information on the parent and all fragment ions. This maintains a balance between the quantity of simultaneously acquired data and the sensitivity of the method, which is beneficial under coupling with analytical chromatography. In this study, characteristic peptides were selected for casein, ovalbumin, and collagen, which are the most commonly used binder proteins in the artworks. A simplified sample preparation protocol including only protein extraction and trypsinization was tested and successfully implemented. The combination of analytical chromatography with bbCID MS technique is a lower cost alternative to the use of high-end nano-LC-MS approaches in the investigation of cultural heritage objects of regional or local importance, e.g., prior to and/or during restoration works. It was demonstrated that, for the paint coating samples, the required level of sensitivity could be acquired through the data-independent MS/MS strategy. The proposed approach was tested on a sample obtained during the restoration work at the Gromov cottage in the Lopukhin Garden (middle of the XIX century). As a result, the main protein component, collagen, was identified using 6 characteristic peptides, which may indicate the use of gelatin-based glue. For instance, the identification of the peptide GVQGPPoxGPAGPR of the incoming collagen composition α-1 was undertaken by three parameters: m/z of the precursor ion of 553.2910, m/z of the fragment ion y9 of 821.4238, and retention time of 1.9 min.