Infos Lab' septembre 2025

Dimitra Markovitsi et ses collaborateurs ont publié  récemment un article dans Physical Chemistry Chemical Physics  "Ultrafast dynamics of the UV-induced electronic relaxation in DNA guanine-thymine dinucleotides: from the Franck-Condon states to the minima of the potential energy surfaces"

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We study the DNA dinucleotide 5′-dGpdT-3′ (abbreviated as GT) as a model system for the relaxation of the electronic excited states in stacked nucleobases. Quantum chemistry calculations determine the Franck–Condon states and follow their evolution along the potential energy surfaces of the two most stable conformers. Three minima, corresponding to an excited charge transfer (1CT) state, a 1ππ* state located on the guanine moiety and a 1nπ* state on the thymine moiety, are identified. Their spectral features are detected in the transient absorption spectra (TAS) recorded for buffered aqueous solutions between 330 and 650 nm with a time-resolution of 30 fs upon excitation at 266 nm. The striking difference between the TAS obtained for GT and an equimolar mixture of the corresponding mononucleosides indicates that the nucleobases are stacked in the majority of the dinucleotide molecules. The 1CT state, in which a charge of 0.8 a.u. is transferred from the guanine to the thymine, is stabilized within 120 fs. The comparison of the GT behaviour with that of 5′-dTpdG-3′, characterized by an opposite polarity and studied previously by the same methodology, reveals that, when the guanine is positioned at the 5′ end, the lifetime of the G+ → T− 1CT state is longer and the corresponding quantum yield higher.

Michèle Desouter-Lecomte et ses collaborateurs ont publié récemment un article dans The Journals of chemicals Physics "Wavepacket and reduced-density approaches for high-dimensional quantum dynamics: Application to the nonlinear spectroscopy of asymmetrical light-harvesting building blocks"

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Excitation-energy transfer (EET) and relaxation in an optically excited building block of poly(phenylene ethynylene) (PPE) dendrimers are simulated using wavepackets with the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method and reduced-density matrices with the hierarchical equations of motion (HEOM) approach. The dynamics of the ultrafast electronic funneling between the first two excited electronic states in the asymmetrically meta-substituted PPE oligomer with two rings on one branch and three rings on the other side, with a shared ring in between, is treated with 93-dimensional ab initio vibronic-coupling Hamiltonian (VCH) models, either linear or with bilinear and quadratic terms. The linear VCH model is also used to calibrate an open quantum system that falls in a computationally demanding non-perturbative non-Markovian regime. The linear-response absorption and emission spectra are simulated with both the ML-MCTDH and HEOM methods. The latter is further used to explore the nonlinear regime toward two-dimensional spectroscopy. We illustrate how a minimal VCH model with the two main active bright states and the impulsive-pulse limit in third-order response theory may provide at lower cost polarization-sensitive time-resolved signals that monitor the early EET dynamics. We also confirm the essential role played by the high-frequency acetylenic and quinoidal vibrational modes.

Baptiste Etcheverry, Marc Baaden (LBT, Paris), Aurélien de la Lande et Fabien Cailliez ont publié récemment un article dans Journal of Chemical Information and Modeling "NOX Transmembrane Electron Transfer Is Governed by a Subtly Balanced, Self-Adjusting Charge Distribution"

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NADPH oxidases (NOX) form a family of transmembrane enzymes that catalyze the formation of reactive oxygen species. These are produced by a chain of electron transfers (ET), shuttling electrons from one side of the membrane to the other, using one flavin and two heme cofactors as redox mediators. In this work, we investigate the thermodynamics of the electron transfer (ET) between the two hemes contained in the transmembrane domain by means of extensive molecular dynamics simulations. We compare two proteins of the NOX5 isoform, from Homo sapiens (hNOX5) and from Cylindrospermum stagnale (csNOX5), a cyanobacteria. We study in detail the influence of both the density of negatively charged lipids in the membrane and of the NOX5 amino acid sequence on the ET thermodynamic balance. The linear response formalism allows us to decompose the variation in free energy into the individual contributions of the system components (protein, membrane, solvent, etc.). We highlight the major compensatory effects of the various components in the global free energy budget for those complex systems. Although the contributions of the protein or the membrane to the ET thermodynamics can be individually strongly modified by a change in the amino acid sequence or the membrane composition, they are largely compensated by the rest of the heme environment so that the total free energy is always found to be slightly favorable to the electron transfer. To our knowledge, this study is the first to highlight the effect of membrane charge density on interheme ET, providing valuable insights into the molecular mechanisms governing ET catalysis in complex membrane systems.

Myriam Bonose, Alain Tchapla et leurs collaborateurs ont publié récemment un article dans la Revue RAMReS : Pharmacopée et médecine traditionnelle africaine "A multi-analytical approach for the chemical characterization of copal Mbaka from Guibourtia demeusei (Harms) J.Leonard"

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Copal from the Mbembe forest in the north of the Republic of Congo, known locally as “Mbaka”, is traditionally used fresh as an adhesive and to light repellent fires. This copal, produced by Guibourtia demeusei (Harms) J.Leonard, has physical characteristics similar to those of other copals exported and studied in Europe, but has never been studied chemically. The main aim of this work is therefore to chemically characterize this copal using a multi-analytical approach. Infrared analyses confirmed that this copal is a terpenoid resinous exudate. Analysis of the volatile fraction, obtained either by hydrodistillation (HD) or headspace solid-phase microextraction (HS-SPME), revealed the presence of monoterpenes, sesquiterpenes and diterpenes. The essential oil of this copal consists mainly of sesquiterpenes with a majority of β-caryophyllene (40%). Using two-dimensional gas chromatography (GCxGC), 19 additional minor compounds were identified compared to the 1D GC results. Non-volatile organic compounds were extracted using Soxhlet, then processed before analysis by high-temperature gas chromatography with mass spectrometric detection (HT-GC-MS). They are labdane-type diterpenic acids. The presence of cativic acid distinguishes this copal from other Congolese copals, and its non-volatile fraction shows similarities to copal samples from Latin America, particularly those from the genus Hymenaea.

Kaouther Ben Arfa, Marie-Claude Menet, Fathi Moussa et leurs collaborateurs ont publié  récemment un article dans Chemistry & Biodiversity "Chemical Profiles and Antifungal Potential of Essential OilsExtracted From the Flower Buds of Eleven EucalyptusSpecies"

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The phytochemical profile of Eucalyptus flower buds (FBs) is not well documented. In this study, we investigated the essential oils (EOs) present in the FBs of 11 Eucalyptus species cultivated in Tunisia. We focused on EO yield via hydrodistillation, chemical composition using GC–MS, and potential antifungal activity. EO yields ranged from 0.71% (Eucalyptus gomphocephala) to 5.3% (Eucalyptus oleosa) (median, 2.9%). Notably, the FBs contained approximately 2.7 times more terpenoids than the leaves. The numbers ranged from 27 (Eucalyptus gracilis) to 40 (E. oleosa). Eucalyptol, α-pinene, para-cymene, aromadendrene, and globulol were present in all species, and their relative abundances enable identification and classification, as confirmed by a principal component analysis (PCA) model. EO of Eucalyptus salubris is the most active against Fusarium oxysporum, whereas Eucalyptus sargentii and Eucalyptus torquata are the most active against Fusarium culmorum and Rhizoctonia solani. Overall, our results suggest that antifungal activity is species-specific and associated with EO composition.

Vien-Duong Quach,  Marija Knezevic, Christophe Colbeau-Justin, Mohamed Nawfal Ghazzal et leurs collaborateurs ont publié récemment un article dans Advanced Science "Oxygen Vacancy Formation at Metal‒TiO₂ Interface Yielding Enhanced Photocatalytic Hydrogen Generation"

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Strong Metal-Support Interaction (SMSI) is a key concept in heterogeneous catalysis, but it remains underexplored in the context of photon-to-hydrogen conversion, as coupling of metallic nanoparticles with photocatalysts is overlooked and only discussed in terms of Schottky barrier formation. In this study, we provide deep insights into the effect of Au encapsulation with TiO2 overlayer on enhancing photocatalytic hydrogen generation. Our findings reveal that the construction of a SMSI-like nanostructure induces the formation of oxygen vacancies at the Au‒TiO2 interface which actively facilitate charge carrier separation through interfacial band reconstruction. The presence of defects is evidenced by Electron Paramagnetic Resonance and X-ray Photoelectron Spectroscopy, unveiling their relationship with photocatalytic activities. Consistent with experimental results, Density Functional Theory (DFT) calculations demonstrate that Au promotes oxygen vacancy formation. These vacancies located at the TiO2 surface significantly enhances H2O and MeOH adsorption during H2 evolution reactions. The SMSI-like concept was extended to Pt, Pd, and Ag, in which the oxygen vacancy formation energy at the metal-semiconductor interface varied depending on the metal, as computed by DFT. The results suggest that photocatalytic activity is related to the ease of oxygen vacancy formation, which is influenced by the nature of the metals.

Fathi Moussa a recement publié sur invitation un article dans Nanomaterials "A Regulatory-Compliant Genotoxicity Study of a Mixture of C60 and C70 Fullerenes Dissolved in Olive Oil Using the Mammalian Micronucleus Test"

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Although they show great promise in the medical field, the safety of fullerenes—discovered forty years ago—is still uncertain, according to regulatory experts at the European Scientific Committee on Consumer Safety. This is a major obstacle to progress in the field. Meanwhile, oily solutions of fullerenes intended for human and pet consumption can be purchased online, without any marketing authorization. Therefore, to avoid any potential public health issues, regulatory-compliant preclinical studies on fullerene oily solutions are urgently needed. We present the first in vivo genotoxicity study of a C60/C70 fullerene mixture (4.1/1, w/w) dissolved in extra virgin olive oil (0.8 mg/mL). The study was conducted using the Mammalian Micronucleus Test (MMT) in an independent GLP-laboratory, in compliance with the OECD and EPA guidelines. The MMT was performed on NMRI mice following the oral administration of fullerenes at doses of up to 3.6 mg/kg. This dose is almost the maximum dose that can be administered to rodents. The data obtained clearly show that fullerene oily solutions have no genotoxic activity under these conditions. This should pave the way for further regulatory investigations of fullerene oily solutions.

La soutenance de thèse de Julia Attard intitulée " Étude par simulation moléculaire des propriétés photophysique de chlorophylles en phase gazeuse" se déroulera le mardi 16 septembre à 14h en salle Magat. 

Les chlorophylles jouent un rôle central dans les processus de conversion de l’énergie lumineuse lors de la photosynthèse. Le but de ce travail est de comprendre les propriétés électroniques et vibrationnelles des chlorophylles en phase gazeuse. Ainsi, cette thèse explore, à travers des approches computationnelles avancées pour aider à interpréter des données expérimentales récentes, les propriétés structurales et photophysiques de la chlorophylle a et de la phéophytine a, à l’état neutre et anionique, en phase gazeuse.

Au cœur de l'ICP, la plateforme MUSIICS propose 2 visites insolites organisées par le CNRS le 3 octobre 2025 : "Observer l’invisible : la peau et le cheveu à l’échelle nanométrique". 

Les inscriptions sont possibles jusqu'au 17 septembre (fermeture à 10h00).

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L’Institut DataIA et la Direction de l’Innovation Pédagogique (DIP) de l'Université Paris-Saclay vous invitent à une journée consacrée aux impacts de l’intelligence artificielle : transformation des pratiques pédagogiques et des formations à l'Université Paris-Saclay.

Date : mardi 23 septembre 2025 (9h30 à 20h) - Lieu : Théâtre Rousseau de CentraleSupélec

Les inscriptions sont désormais clôturées mais si vous souhaitez vous inscrire sur file d'attente vous pouvez remplir le questionnaire suivant : https://framaforms.org/liste-dattente-journee-impact-de-lia-transformation-des-pratiques-pedagogiques-et-des-formations-a. 

Le prochain webinaire de la subdivision de Chimie Analytique de la DCP (SCF/SFP) aura lieu le 25 septembre 2025 de 11h à 12h30 et portera sur l’Analyse de la matière organique dissoute et complexe, avec la participation de deux orateurs 

• Justine Criquet (Prof, LASIRE, Université de Lille) “Caractérisation de la matière organique et de ses produits de transformation dans les filières de potabilisation”
• Maxime Bridoux (IR, CEA, Bruyères-le-Chatel) “Caractérisation de mélanges complexes par spectrométrie de masse ultrahaute résolution”

Pour recevoir le lien de connexion, l'inscription est obligatoire en remplissant le formulaire que vous trouverez à l'adresse suivante: https://cnrs.zoom.us/meeting/register/2rtBOyrBS2Ki77JT1yA_XA

Les premières journées scientifiques du PEPR LUMA sont ouvertes à toute la communauté œuvrant dans le domaine des interactions lumière-matière. Elles auront lieu à Paris les 1er et 2 octobre à Sorbonne Université. L'ICP participera à l'animation de la table ronde "plateforme et recherche" du 2 octobre. L'inscription est gratuite et ouverte jusqu'au 15 septembre. Programme et Inscription

La section Ile-de-France du réseau Jeunes de la SCF continue sa série de webinaires sur différentes thématiques couvertes par la Société Chimique de France. Le prochain webinaire aura pour thème la Chimie analytique et aura lieu le jeudi 9 octobre de 13h à 14h. Les stagiaires de M2, les doctorant(e)s et les post-doctorant(e)s qui travaillent sur cette large thématique sont les bienvenu(e)s pour présenter leurs travaux. Les présentations sont d’environ 10 minutes suivies de 5 min de questions, afin de favoriser un dialogue entre les participants, tout en restant sur un format court. L’objectif est de prendre connaissance des recherches d’autres équipes dans le secteur IdF et favoriser les échanges entre ces labos.

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Contact : Florent Ducrozet

Lucie Arberet, Lea-Maria Ibele, Alain Tchapla, Federica Agostini, Sylvie Héron et leurs collaborateurs ont publié récemment un article dans Journal of Molecular Structure: "Structural elucidation of the main coloured compounds of Justicia spicigera based on experimental and computational electronic features"

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In continued efforts to characterise the dye extracted from Justicia spicigera leaves, the two main coloured compounds were isolated. In this study, a multi-analytical techniques characterisation of their structures was carried out by HRMS, NMR, vibrational (IR and Raman) and electronic (UV–Vis absorption and fluorescence) spectroscopies, completed by computational studies. Two unreported compounds from the phenoxazone (aka phenoxazine-3-one) family were identified, the 2-amino-7‑hydroxy-8‑methoxy-3H-phenoxazin-3-one, a positional isomer of the already described perisbivalvin B and the 2-N-(4‑hydroxy-γ-glutamyl)-7‑hydroxy-8‑methoxy-3H-phenoxazin-3-one. The simulated UV–Vis absorption and fluorescence spectra of the suggested structures showed good agreement with the experimental ones, supporting the structural elucidation and giving more insights into the chemistry of these compounds.

Isabelle Lampre, Christophe Humbert, Hynd Remita et leurs collaborateurs ont publié récemment un article dans Journal of Physics and Chemistry of Solids: "Radiation-induced photoluminescence enhancement of zinc oxide and zinc oxide- polyvinyl alcohol nanocomposite: A green and controllable approach for tailor-made optoelectronics"

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The structural and optical properties of gamma-ray-irradiated ZnO and ZnO-PVA nanocomposites, synthesized via a one-pot method, were investigated. The samples were analyzed before and after irradiation at doses up to 26 kGy using UV–Vis spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and surface frequency generation spectroscopy. X-ray diffraction confirmed the hexagonal wurtzite structure of ZnO, while electron microscopy revealed the embedment of 40 nm ZnO nanoparticles into the PVA matrix. Shifts and decreased ratio of the CH2–CH2 FT-IR vibrations at 1420 cm−1 and combined CH2–CH2/CH2–O–CH2 stretching at 1143 cm−1 indicated not only polymer matrix dislocation resulting from incorporation of ZnO nanoparticles in the PVA matrix but also cross-linking of the polymer chains upon irradiation. Surface frequency generation spectroscopy further confirmed PVA adherence and bonding to ZnO surfaces. Photoluminescence studies revealed significant changes in the energy and intensity of the near-band-edge emission of irradiated ZnO nanoparticles attributed to the annealing of surface defects. UV–Vis spectroscopy of ZnO-PVA showed a dose-dependent absorption increase at 280 nm, suggesting polymer cross-linking. Additionally, the intensity of the blue photoluminescent peak located around 445 nm increased with irradiation dose indicating dose-dependent enhancement of ZnO-PVA bonding. These findings demonstrate that gamma-ray irradiation effectively modifies the optical and surface properties of ZnO-based materials, enhancing their performance for applications in flexible optoelectronics, light-emitting devices, and environmental sensors. The ability to precisely control material properties through irradiation offers new opportunities for developing advanced functional materials with improved performance and sustainability.

Nicolas Solem, Roland Thissen, Claire Romanzin, Christian Alcaraz et leurs collaborateurs ont publié récemment un article dans ACS Earth and Space Chemistry: "Possible Hydrocarbon Chemical Growth Routes from l-C3H+ in Dense Molecular Clouds"

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The C3H+ cation plays a pivotal role within the chemical network of dense interstellar clouds. Its relatively slow reaction with molecular hydrogen (H2) suggests that reactions with other species, particularly small hydrocarbons, may play a significant role. In this study, we measured the absolute reaction cross sections of C3H+ with acetylene (C2H2) and the two isomers of C3H4 (allene and propyne). To facilitate the implementation of our experimental data into astrochemical models, we converted the reaction cross sections into rate constants. No temperature dependency was observed for all of the investigated channels. The reaction rates for C3H+ with C2H2 and C3H4, yielding C5H2+ and C4H3+, respectively, are in good agreement with existing data. However, we report a previously unidentified channel in the reaction with C3H4, leading to protonated acetylene C2H3+ with a 30% yield compared to the major product, C4H3+.

Claire Romanzin, Nicolas Solem, Roland Thissen, Christian Alcaraz et leurs collaborateurs ont publié récemment un article dans ACS Earth and Space Chemistry: "The Experimental Rate Constant of the S+(2D) + H2 Reaction"

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Endothermic reactions such as S+(4S) + H2 are not expected to play a significant role in the chemistry of the interstellar medium (ISM). However, in some specific environments, such as photon-dominated regions (PDR), UV radiation may catalyze the reaction by providing enough internal energy to reactants to overcome endothermicity. For instance, it was recently shown that the vibrational excitation of H2 greatly enhances the reactivity of C+ and S+ with H2, explaining the presence of their respective hydrides CH+ and SH+ in these regions. However, vibrational excitation of H2 is not a unique way to enhance the reactivity by UV radiation. Electronic excitation is an alternative way to effectively inject a huge amount of internal energy into the system, thus favoring reactivity. In this work, we will address how electronic excitation of the sulfur cation can strongly enhance the production of SH+. This is done by measuring experimentally the cross section of the title reaction for collision energies from 50 meV up to several eV and comparing the results with theoretical predictions in the 0.001–3 eV range. The reaction cross section is then used to derive the rate constant for a wide range of temperatures.