Session: Session 4

A FILTER-ASSISTED FRACTIONATION STRATEGY TO IDENTIFY PLANT GUMS POLYSACCHARIDES AND GLYCOPEPTIDES

Nicolas ESKENAZI¹, Theodora MAVROGIANNI^1,2, Agnès LATTUATI-DERIEUX², Joëlle VINH¹

¹Spectrométrie de Masse Biologique et Protéomique, LPC, UMR ESPCI CNRS 8249, Paris, France
²Centre de Recherche et de Restauration des Musées de France (C2RMF), Département Recherche, Palais du Louvre / IRCP UMR CNRS 8247, Paris, France

Plant gums are commonly found in heritage objects, serving as ideal polychromy binder due to their physical properties and the presence in the surrounding nature of the shrubs which provide these exsudations . Understanding their origin and composition is crucial for preservation and restoration efforts and for improving our knowledge of the recipes used in the past. The gold standard for identifying gum involves acid methanolysis followed by GC-MS analysis of the gum's monosaccharides. While highly informative about the gum's composition and vegetal origin, this approach faces challenges, particularly in characterizing heterogeneous assemblages of different gums or species with similar monosaccharide content.

Recent methods have been developed to complement the GC-MS approach by identifying these gums from their glycosidic profiles using MALDI-TOF MS (Granzotto, 2017). In this method, sugars are derivatized on-target using various 3-aminoquinoline liquid matrices (Fukuyama, 2014). To this end, we have created a library of oligosaccharide spectral fingerprints for several modern gums from Acacia, Ceratonia, Astragalus and Prunus genus. Using this library in conjunction with GC-MS data, we previously identified tragacanth gum from the polychromy of the coffin of Djedmut, a cantatrice of Amon-Rê from Ancient Egypt (ca. 945-900 BCE).

Despite their informative value, these approaches can encounter limitations when multiple species and subspecies produce gums with similar or identical polysaccharide moieties. To address this, we interfaced enzymatic deglycosylation and oligosaccharide MALDI-TOF analysis with proteolysis and identification of the minor (5% or less) protein fraction. We successfully sequenced the polar glycopeptides from reference gums by employing a bottom-up approach with a fractioning protocol analogous to FASP (Filter-Assisted Sample Preparation). We aim to possibly use them as markers for these species in combination with GC-MS and MALDI-MS data.