Proteomics protein identification in a painting

I hate to tell you - but all that has been keeping us stuck in this fresco for 100 years is a bit of egg glue. 

Technique Electrospray QTOF with DDA for peptide sequencing. 

Reference A. Chambery, A. Di Maro, C. Sanges, V. Severino, M. Tarantino, A. Lamberti, A. Parente, and P. Arcari, Improved procedure for protein binder analysis in mural painting by LC-ESI/Q-q-TOF mass spectrometry Detection 

Background Understanding the biochemistry of objects of cultural heritage contributes to our historical knowledge and provides information for the conservation of art. This paper reports on the identification of proteinaceous binders in a mural in the St. Dimitar Cathedral in Vidin, Bulgaria, that was probably painted by Kiril Jeliaskov in the early twentieth century. 

Homemade tempera paints were prepared according to old recipes dating from 1859 (egg based) and 1894 (milk based) in the latter, sheep, goat, and bovine milk were used. Mixtures of milk and egg tempera were placed on microscope slides and dried at room tanperature. It was shown that 1 pg of egg protein was required to give good quality MS/MS spectra, appropriate for protein identification. 

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