Inez Dorothé van der Werf

A simple protocol for Matrix Assisted Laser Desorption Ionization- time of flight-mass spectrometry (MALDI-TOF-MS) analysis of lipids and proteins in single microsamples of paintings

A simple protocol, based on Bligh-Dyer (BD) extraction followed by MALDI-TOF-MS analysis, for fast identification of paint binders in single microsamples is proposed. For the first time it is 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 (RapiGest™) in order to improve efficiency of protein digestion and purification step. Detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (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. Finally, the proposed protocol was successfully applied to the study of a late-15th century Italian panel painting allowing the identification of various proteinaceous and lipid sections in organic binders, such as egg yolk, egg white, animal glue, casein, and drying oil.

Synthesis and analytical characterisation of copper-based nanocoatings for bioactive stone artworks treatment

AbstractBiological agents play an important role in the deterioration of cultural heritage causing aesthetic, biogeophysical and biogeochemical damages. Conservation is based on the use of preventive and remedial methods. The former aims at inhibiting biological attack, and the latter aims at eradicating the biological agents responsible for biodeterioration. Here, we propose the preparation and the analytical characterisation of copper-based nanocoating, capable of acting both as a remedy and to prevent microbial proliferation. Core–shell CuNPs are mixed with a silicon-based product, commonly used as a water-repellent/consolidant, to obtain a combined bioactive system to be applied on stone substrates. The resulting coatings exert a marked biological activity over a long period of time due to the continuous and controlled release of copper ions acting as biocides. To the best of our knowledge, this is the first time that a multifunctional material is proposed, combining the antimicrobial properties of nanostructured coatings with those of the formulations applied to the restoration of stone artworks. A complete characterisation based on a multi-technique analytical approach is presented. Online abstract figureRelease properties and morphological features of copper-based nanocoatings.

A multianalytical study of archaeological faience from the Vesuvian area as a valid tool to investigate provenance and technological features

The investigation was aimed at defining the compositional and structural characteristics of a group of monochrome blue faiences recovered in Pompeii to assess provenance on the basis of their technological features. Different complementary analytical techniques were used: Scanning Electron Microscopy (SEM) to investigate the morphological aspects of the samples and in particular of the interfaces, micro-Raman Spectroscopy and XRPD to identify crystalline phases and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) to assess the elemental composition due to its sensitivity to a wide range of elements and the adequate lateral resolution. Statistical data treatment of the elemental concentrations of both the ceramic bodies and the glazes allowed us to classify the objects into compositional groups and to verify the previously established archaeological hypothesis suggesting an Egyptian provenance for faience of Pompeii.

Characterization and behaviour of ZnO-based nanocomposites designed for the control of biodeterioration of patrimonial stoneworks

In this study, a preventive method for fighting bio-deterioration of stone substrates is proposed. This is based on the use of bioactive zinc oxide nanoparticles (ZnO-NPs), which are able to exert a marked biological activity over a long period of time due to their peculiar structure. ZnO-NPs are synthesised by a simple and reproducible electrochemical procedure. The nanomaterials are embedded in consolidant/water-repellent matrices to obtain nanostructured coatings. Commonly used products based on tetraethoxysilane and/or polysiloxanes were tested. The resulting nanomaterials were fully characterised by X-ray photoelectron spectroscopy (XPS) to investigate the amount and composition of the NPs and the behaviour of the nanocomposites. Inductively coupled plasma mass spectrometry (ICP-MS) was used for the study of the release of metal from the composites when put in contact with artificial rainwater. The nanocomposites were applied to specimens composed of three different types of stone and chromatic changes upon curing were measured by spectrophotocolorimetry. Finally, morphological characterization by scanning electron microscopy (SEM) was performed. The bioactivity of ZnO-NPs nanocomposites was also assessed in preliminary tests against Aspergillus niger fungus.

Characterisation of permanent markers by pyrolysis gas chromatography–mass spectrometry

Pyrolysis gas chromatography–mass spectrometry (PyGC-MS) was used as a rapid method for the characterization of permanent marker ink. Twenty-four samples of various colours purchased from different manufacturers were characterised. Four main typologies of polymer-binding medium could be distinguished on the basis of the pyrolysis products, and differentiation between permanent markers of different manufacturers could be accomplished. For some permanent marker samples, PyGC-MS analysis allowed pigment identification as well.

Revealing the composition of organic materials in polychrome works of art: the role of mass spectrometry-based techniques

The most recent advances in the identification and determination of organic constituents in paintings and other polychrome objects using mass spectrometry (MS)-based techniques are reviewed. The latest achievements in gas chromatography (GC)-MS and pyrolysis (Py-) GC-MS are mainly related to sample pretreatment protocols and to the employment of double-shot or laser desorption pyrolysis, respectively. MS techniques based on soft ionization methods such as matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) are discussed. So far, MALDI and ESI MS have been mainly used in the characterization of proteinaceous materials, but further applications are definitely emerging, e.g., in the fields of lipids, resins, and organic colorants analysis. Chemical imaging by time-of-flight secondary ion mass spectrometry (TOF SIMS), formerly applied to the detection and localization of lipid binders and inorganic materials, has been recently extended to proteins. Finally, the potential of niche techniques such as direct temperature resolved mass spectrometry (DTMS) and direct analysis in real time (DART) MS are outlined.

Chemical composition of felt-tip pen inks

Felt-tip pens are frequently used for the realization of sketches, drawings, architectural projects, and other technical designs. The formulations of these inks are usually rather complex and may be associated to those of modern paint materials where, next to the binding medium and pigments/dyes, solvents, fillers, emulsifiers, antioxidants, plasticizers, light stabilizers, biocides, and so on are commonly added. Felt-tip pen inks are extremely sensitive to degradation and especially exposure to light may cause chromatic changes and fading. In this study, we report on the complete chemical characterization of modern felt-tip pen inks that are commercially available and commonly used for the realization of artworks. Three brands of felt-tip pens (Faber-Castell, Edding, and Stabilo) were investigated with complementary analytical techniques such as thin-layer chromatography (TLC), VIS-reflectance spectroscopy, μ-Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), GC–MS, and Fourier transform infrared (FTIR) spectroscopy. The use of TLC proved to be very powerful in the study of complex mixtures of synthetic dyes. First derivatives of the reflectance spectra acquired on the TLC spots were useful in the preliminary identification of the dye, followed by Raman spectroscopy and SERS, which allowed for the unambiguous determination of the chemical composition of the pigments (phthalocyanines, dioxazines, and azo pigments) and dyes (azo dyes, triarylmethanes, xanthenes). FTIR spectroscopy was used especially for the detection of additives, as well as for confirming the nature of solvents and dyes/pigments. Finally, (Py–)GC–MS data provided information on the binders (styrene–acrylic resins, plant gums), solvents, and additives, as well as on pigments and dyes.

On plate graphite supported sample processing for simultaneous lipid and protein identification by matrix assisted laser desorption ionization mass spectrometry

The simultaneous identification of lipids and proteins by matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) after direct on-plate processing of micro-samples supported on colloidal graphite is demonstrated. Taking advantages of large surface area and thermal conductivity, graphite provided an ideal substrate for on-plate proteolysis and lipid extraction. Indeed proteins could be efficiently digested on-plate within 15 min, providing sequence coverages comparable to those obtained by conventional in-solution overnight digestion. Interestingly, detection of hydrophilic phosphorylated peptides could be easily achieved without any further enrichment step. Furthermore, lipids could be simultaneously extracted/identified without any additional treatment/processing step as demonstrated for model complex samples such as milk and egg. The present approach is simple, efficient, of large applicability and offers great promise for protein and lipid identification in very small samples.

Profile of microbial communities on carbonate stones of the medieval church of San Leonardo di Siponto (Italy) by Illumina-based deep sequencing

Comprehensive studies of the biodiversity of the microbial epilithic community on monuments may provide critical insights for clarifying factors involved in the colonization processes. We carried out a high-throughput investigation of the communities colonizing the medieval church of San Leonardo di Siponto (Italy) by Illumina-based deep sequencing. The metagenomic analysis of sequences revealed the presence of Archaea, Bacteria, and Eukarya. Bacteria were Actinobacteria, Proteobacteria, Bacteroidetes, Cyanobacteria, Chloroflexi, Firmicutes and Candidatus Saccharibacteria. The predominant phylum was Actinobacteria, with the orders Actynomycetales and Rubrobacteriales, represented by the genera Pseudokineococcus, Sporichthya, Blastococcus, Arthrobacter, Geodermatophilus, Friedmanniella, Modestobacter, and Rubrobacter, respectively. Cyanobacteria sequences showing strong similarity with an uncultured bacterium sequence were identified. The presence of the green algae Oocystaceae and Trebuxiaceae was revealed. The microbial diversity was explored at qualitative and quantitative levels, evaluating the richness (the number of operational taxonomic units (OTUs)) and the abundance of reads associated with each OTU. The rarefaction curves approached saturation, suggesting that the majority of OTUs were recovered. The results highlighted a structured community, showing low diversity, made up of extremophile organisms adapted to desiccation and UV radiation. Notably, the microbiome appeared to be composed not only of microorganisms possibly involved in biodeterioration but also of carbonatogenic bacteria, such as those belonging to the genus Arthrobacter, which could be useful in bioconservation. Our investigation demonstrated that molecular tools, and in particular the easy-to-run next-generation sequencing, are powerful to perform a microbiological diagnosis in order to plan restoration and protection strategies.

A multi-analytical approach for the assessment of the provenience of geological amber: the collection of the Earth Sciences Museum of Bari (Italy)

The Earth Sciences Museum of the University of Bari Aldo Moro (Italy) exhibits a wide collection of amber samples. These have been catalogued as Baltic amber (succinite), Sicilian amber (simetite), amber from New Jersey, Apennine amber and New Zealand copaline. However, some samples revealed to be erroneously classified as a consequence of incorrect information on the labels or in the museum catalogue. This may be due to historical forgeries, as is often the case of simetite, or to a possible exchange of samples that probably occurred during the displacement of the museum collection from the Central University Building to the Geo-environmental and Earth Sciences Department. In this study, all amber samples were systematically investigated with long wave UV rays, attenuated total reflectance (ATR), Fourier transform infrared (FTIR) spectroscopy and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) using on-line thermally assisted hydrolysis and methylation. The combined use of the latter two analytical techniques allowed for a complete characterisation of the ambers, whereas UV fluorescence showed to be of little value. The compositional data could be used for a better classification and valorisation of the amber samples of the museum collection. Two of the purported amber samples were shown to be copal, while four others are ambers but had been wrongly classified. Moreover, for some samples, it could be established that they had been subjected to treatment with a drying oil.