New protocols for
MALDI-MS of lipids and proteins contained in a single small
specimen of paint were developed.
The first protocol is based on Bligh–Dyer (BD) extraction
followed by MALDI-TOF-MS analysis. For the first time it was
demonstrated that the BD method is effective for the
simultaneous extraction of lipids and proteins from complex, and
atypical matrices, such as pigmented paint layers. The protocol
makes use of an alternative denaturing anionic detergent (RapiGestTM)
in order to improve efficiency of protein digestion and
purification step. Detection of various lipid classes, such as
TAGs and PLs and their oxidation by-products, was accomplished,
whereas proteins could be identified by peptide mass
fingerprinting. The effect of pigments on ageing of lipids and
proteins was also investigated.
The second protocol contributes a step forward in the
simplification of such a protocol as no conventional solvent
extraction is required. The paint fragment (ca. 100 μg) is fixed
on the MALDI target plate, and the wet chemistry steps required
for protein digestion are performed directly on the plate that,
after matrix addition, was analyzed by MALDI-MS for the
simultaneous identification of proteinaceous and lipid markers
of the most commonly used binders. Colloidal graphite is used to
assure the adhesion of the painting fragment (as such or after
grinding) on a conventional stainless steel target plate.
The potential of both protocols was demonstrated analyzing
samples taken from different paintings.
• Calvano C.D., van der Werf I.D., Palmisano F., Sabbatini L., "Identification
of lipid- and protein-based binders in paintings by direct
on-plate wet chemistry and matrix-assisted laser desorption
ionization mass spectrometry", Analytical and Bioanalytical
Chemistry, 407 (2015) 1015–1022.
• Cosima Damiana Calvano, Inez Dorothé van der Werf, Luigia
Sabbatini, Francesco Palmisano, On plate graphite supported
sample processing for simultaneous lipid and protein
identification by matrix assisted laser desorption ionization
mass spectrometry, Talanta, DOI: 10.1016/j.talanta.2015.01.030
• I.D. van der Werf, A. Monno, C.D. Calvano, R. Laviano, L.
Sabbatini, Il polittico di Antonio Vivarini: uno sguardo
scientifico alla materia pittorica, in “Antonio Vivarini in
Puglia” (a cura di C. Gelao), Marsilio editore, Venezia, 2014
(ISBN: 978-88-317-1879-0) pp. 77-89.
• V. Sajeva, Sviluppo di protocolli innovativi per
l’identificazione di leganti pittorici mediante tecniche di
spettrometria di massa MALDI-TOF, MSc thesis, 2013-2014,
University of Bari Aldo Moro