Investigation of proteins in samples of a mid-18th century colonial mural painting by MALDI-TOF and nano-LC-ESI-hybrid-Q-orbitrap mass spectrometry

LEVY, I.K.; NEME TAUIL, R; MORENO, S.; SIRACUSANO, G.; MAIER, M.

Bilbao

Congreso; Technart 2017 (Non.destructive and microanalytical techniques in art and culture heritage; 2017

Department of Analytical Chemistry, University of The Basque Country

Investigationof proteins in samples of a mid-18th century colonial mural painting byMALDI-TOF and nano-LC-ESI-hybrid-Q-orbitrap mass spectrometryIvana K. Levy(1), Ricardo Neme Tauil(2),Silvia Moreno(2), Gabriela Siracusano(3) and Marta S.Maier(1,3)(1) Universidad de Buenos Aires, Consejo Nacional deInvestigaciones Científicas y Técnicas, Unidad de Microanálisis y MétodosFísicos en Química Orgánica (UMYMFOR), Facultad de Ciencias Exactas yNaturales, 1428, Ciudad Autónoma de Buenos Aires, Argentina(2) Universidadde Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas,Centro de Estudios Químicos y Biológicos por Espectrometría de Masa, Facultadde Ciencias Exactas y Naturales,1428, Ciudad Autónoma de Buenos Aires,Argentina(3) Centro de Investigación en Arte, Materia yCultura (IIAC), Universidad Nacional de Tres de Febrero, Avenida AntártidaArgentina 1355 (C1104ACA), Ciudad Autónoma de Buenos Aires, Argentina.  With the aim of investigating the presenceof proteinaceous materials in a wall painting from the church of Our Lady ofCopacabana de Andamarca (1723) in Bolivia, seven micro-samples have been extractedbefore the restoration. Historically, artists have used different proteinaceousbinders as egg, casein, and animal glues, depending on the painting techniqueand their availability. Identification of proteinaceous binders plays animportant role in conservation and offers insights into the manufacturingtechnique of a work of art.In this investigation, we report for the firsttime the application of proteomic tools to the study of colonial samples. Theanalysis of proteinaceous binders was performed on references, model samplesand micro-samples from a wall painting. In the first stage of our study, weapplied MALDI-TOF mass spectrometry and then, we used nano-LC-ESI-hybrid-Q-orbitrapto achieve more reliability in the identification of the protein binders. By MALDI, we found weak signals presumablyof egg peptides in several of the micro- samples. By nano-LC-ESI-hybrid-Q-orbitrap,one sample yielded several peptides from seven egg white different proteins,particularly ovoalbumin, ovotransferrin, lysozyme, and two egg yolk proteins,vitellogenin-2 and apolipoprotein B, were detected in another sample with onehigh confidence peptide each. These results confirm our previous GC-MS results indicatingthat egg tempera was used as the painting technique [1]. In all the samples,the presence of collagen from animal glue was established by MALDI-TOF andnano-LC-ESI-hybrid-Q-orbitrap. This finding supported our previous assumption thatanimal glue was applied as a primer onto the ground layer. In order to identifythe origin of the collagen isoforms, a search against a Uniprot databasecontaining collagen proteins from all the species was performed. The results suggest that this glue was prepared from amixture of several sources.In conclusion, both mass spectrometry techniques areefficient tools for identifying proteinaceous binders in old tempera paintings.The advantage of nano-LC-ESI-hybrid-Q-Orbitrap over MALDI-TOF lies in thehighest accuracy to identify proteins. However, MALDI allowed a quickerscreening and faster comparison between samples and references.[1] E. Tomasini, D. Castellanos Rodríguez, B. Gómez, D. de Faria, C. RúaLanda, G. Siracusano, M. Maier,  Microchemical J. 128, 2016, 172.