Laboratoire d’Archéologie Moléculaire et Structurale

Initially used for fermentation or storage, oak wood barrels were found to enhance the organoleptic properties of spirits. Over time, wood extractives like ellagitanins and aromatic precursors have been linked to the quality of the spirits. TOF-SIMS being an ionization technique produces intense fragmentation patterns that are not fully understood, and reference spectra are required to confidently analyze wood samples. Here, negative polarity TOF-SIMS reference spectra of important oak wood compounds being involved in spirit maturation, using a Bi3+ primary ion species, are presented.

Paints obtained by dispersing pigments in emulsions of egg yolk and vegetable oil have been used by 20th century artists, likely drawing on techniques dating back to the 15th century. Understanding their flow behavior is key to shedding light on artists' material choices, gestures, and the resulting visual effects. In this study, we investigate two modern recipes that yield either oil-in-water (o/w) or water-in-oil (w/o) emulsions, formulated with egg yolk and linseed oil-raw or cooked with lead oxide following a historical process designed to accelerate drying. Stable, homogeneous paints were successfully prepared by dispersing lead-tin yellow pigment into these emulsions. The volume fraction of the dispersed phase, which includes solid pigment particles and emulsion droplets, emerged as a critical parameter for stable shear flow. Higher volume fractions resulted in increased yield stress, consistency, and viscosity across a wide range of shear rates. Dynamic rheological measurements further revealed the significant influence of the nature of the continuous phase on the viscoelastic properties of the paints. Finally, confocal microscopy on model systems (using glass microspheres as pigment analogs) showed preferential localization of particles within one emulsion phase. These observations offer new insights into how preparation protocols influence the microstructure-and subsequently the working properties-of historical emulsion paints.

This paper addresses the complementarity and potential disparities between single-molecule and ensemble-average approaches to probe the binding mechanism of oligopeptides on inorganic solids. Specifically, we explore the peptide/gold interface owing to its significance in various topics and its suitability to perform experiments both in model and real conditions. Experimental results show that the studied peptide adopts a lying configuration upon adsorption on the gold surface and interacts through its peptidic links and deprotonated thiolate extremities, in agreement with theoretical predictions. Single-molecule force spectroscopy (SMFS) measurements revealed the existence of a wide panel of adhesion forces, resulting from the interaction between individual peptide moieties and the abundant surface sites. We therefore propose methodological developments for sorting the events of interest to understand the peptide adsorption mechanism. Thermodynamic and kinetic aspects of the peptide adsorption are probed using both static and dynamic force spectroscopy measurements. Specifically, we show the possibility of providing a reasonable estimate of the peptide free energy of adsorption ΔadsG° by exploring the fluctuations of the adhesion work, based on the Jarzynski equality, and by using a parametric Gamma estimator. The proposed approach offers a relevant method for studying the different factors influencing the peptide adsorption and evaluating their impact on ΔadsG° as an alternative to exploring adhesion forces that may lead to misinterpretations. This is illustrated by the comparison of the adsorption of two peptides with specific amino acids substitution. Our method provides insights into the overall mechanism by which peptides interact with the surface and allows an integration of the single-molecule versus ensemble-average points of view.

International audience

Traendo profitto dall’aumento dei dati disponibili sulle produzioni ceramiche della Sicilia islamica e di Palermo in particolare, in questo contributo si propone una analisi delle terminologie impiegate nelle fonti arabe per definire i protagonisti dei rapporti di produzione – artigiani e consumatori – nei mercati della capitale emirale, partendo da un noto passo di Ibn Ḥawqal. L’obiettivo è di riflettere su come la diversa diffusione delle tecniche produttive sull’isola tra X e XI secolo possa aver cambiato anche la percezione stessa della “specializzazione” dell’artigianato ceramico.

This study investigates the alteration processes affecting the smalt pigment in historical artworks through a combination of analytical techniques including X-ray Absorption Near Edge Structure (XANES) spectroscopy at the potassium (K) and cobalt (Co) K-edges, coupled with scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and micro X-ray fluorescence elemental mapping (µ-XRF). Laboratory mock-up samples prepared with different oil binding media were artificially aged, revealing varying rates of smalt degradation. µ-XANES analyses at the K K-edge provided grain-scale insights into smalt alteration, highlighting the influence of binding media composition on degradation kinetics. Crossed clustering data analysis over K µ-XANES acquired on both model samples and historical cross-sections corroborated findings and identified distinct spectral signatures associated with different stages of smalt degradation. Furthermore, identification of potential transformation products such as potassium alum in historical samples emphasized the dynamic nature of pigment alteration processes.

NMDA receptors (NMDARs)are glutamate-gated ion channels playinga central role in synaptic transmission and plasticity. NMDAR dysregulationis linked to various neuropsychiatric disorders. This is particularlytrue for GluN2B-containing NMDARs (GluN2B-NMDARs), which have majorpro-cognitive, but also pro-excitotoxic roles, although their exactinvolvement in these processes remains debated. Traditional GluN2B-selectiveantagonists suffer from slow and irreversible effects, limiting theiruse in native tissues. We therefore developed OptoNAM-3, a photoswitchablenegative allosteric modulator selective for GluN2B-NMDARs. OptoNAM-3provided light-induced reversible inhibition of GluN2B-NMDAR activitywith precise temporal control both in vitro and in vivo on the behaviorof freely moving Xenopus tadpoles.When bound to GluN2B-NMDARs, OptoNAM-3 displayed remarkable red-shiftingof its photoswitching properties allowing the use of blue light insteadof UV light to turn-off its activity, which we attributed to geometricconstraints imposed by the binding site onto the azobenzene moietyof the ligand. This study therefore highlights the importance of thebinding site in shaping the photochemical properties of azobenzene-basedphotoswitches. In addition, by enabling selective, fast, and reversiblephotocontrol of native GluN2B-NMDARs with in vivo compatible photochemicalproperties (visible light), OptoNAM-3 should be a useful tool forthe investigation of the GluN2B-NMDAR physiology in native tissues.

Abstract The opacity/transparency, color, and production of designs in Changsha ware, a Tang dynasty Chinese stoneware renowned for its polychromy and pioneering high‐temperature red glaze, are studied by analyzing the composition, micro/nanostructure, and copper/iron speciation. The results shed new light on some of the most debated questions about Changsha ware. In particular, the role of glaze thickness, composition, and firing conditions on the coexistence of transparent and opaque glazes and of oxidized green and reduced red copper designs on the same object, and on the reason for the development of either green or turquoise colors. New data obtained by reproducing a copper red overglaze and underglaze painting with a similar glaze composition and thickness have provided new insights into the origin of the first high‐temperature copper reds and, in the absence of essential knowledge, their discontinuity. This study also contributes to the long debate regarding the use of overglaze versus underglaze painting techniques.