Catégorie d'actualités : Publications marquantes

Schwartz, A., Rabhi, M., Margeat, E. and Boudvillain, M.
Analysis of Helicase–RNA Interactions Using Nucleotide Analog Interference Mapping
Methods in Enzymology vol 511, 149-169

L’astrochimie étudiée dans son laboratoire naturel : l’espace

L’objectif du projet était d’étudier la nature et l’évolution de la matière organique dans les conditions de l’espace afin de comprendre leurs implications dans l’évolution vers le vivant.
De retour au Centre de Biophysique Moléculaire, les échantillons ont été analysés et les évolutions subies par les molécules exposées ont été identifiées et quantifiées par GC-MS (chromatographie gazeuse couplée à un spectromètre de masse). Cette expérience, a permis de vérifier que le rayonnement ultraviolet était la principale cause de détériorations des composés dans l’espace. Associée à d’autres irradiations effectuées en laboratoires, cette expérience a aussi permis de mieux connaitre les interactions entre les molécules organiques et la matière minérale. En effet, cette dernière peut, en fonction du rayonnement ultraviolet absorbé, protéger les composés de manière importante ou non.
Ainsi, les composés voyageant au sein des météorites, micrométéorites et comètes pourraient en quelque sorte subir une « sélection » durant leur voyage interplanétaire, favorisant sur Terre les molécules les plus résistantes aux conditions de l’espace.

Pour plus d’informations, voir le site de l’INSU

Contact : Marylène Bertrand

[Cottin, H., Noblet, A., Guan, Y.Y., Poch, O., Saiagh, K., Cloix, M., Macari, F., Jérome, M., Coll, P., Raulin, F., Stalport, F., Szopa, C., Bertrand, M., Chabin, A., Westall, F., Chaput, D., Demets, R., Brack, A.
The PROCESS experiment: an astrochemistry laboratory for solid and gaseous organic samples in low Earth orbit.
Astrobiology (2012) 12, 412-425.->doc739]

[Bertrand, M., Chabin, A., Brack, A., Cottin, H., Chaput, D., Westall, F.
The PROCESS Experiment: Exposure of amino acids in the EXPOSE-E experiment on the ISS and in laboratory simulations.
Astrobiology (2012) 12, 426-435. ->doc738]

Zaïm, A., Nozary, H., Guénée, L., Besnard, C.,Lemonnier, J.F., Petoud, S. and Piguet, C.

N-Heterocyclic Tridentate Aromatic Ligands Bound to Ln(hexafluoroacetylacetonate)3 Units: Thermodynamic, Structural, and Luminescent properties

Chemistry a European Journal (2012) 18, 7155-7168

Résumé :

Herein, we discuss how, why,and when cascade complexation reactions produce stable, mononuclear, luminescent ternary complexes, by considering the binding of exafluoroacetylacetonate anions (hfac-) and neutral, semi-rigid, tridentate, 6-bis(benzimidazol-2-yl)pyridine ligands (Lk) to trivalent lanthanide atoms (LnIII). The solid-state structures of Ln(Lk)ACHTUNGTRENUNG(hfac)3] (Ln=La, Eu, Lu) showed that [Ln-ACHTUNGTRENUNG(hfac)3] behaved as a neutral six-coordinate lanthanide carrier with remarkable properties: 1) the strong cohesion between the trivalent cation and the didentate hfac anions prevented salt dissociation; 2) the electron-withdrawing trifluoromethyl substituents limited charge-neutralization and favored cascade complexation with Lk; 3) nine-coordination was preserved for [Ln(Lk)-ACHTUNGTRENUNG(hfac)3] for the complete lanthanide series, whilst a counterintuitive trend showed that the complexes formed with the smaller lanthanide elements were estabilized. Thermodynamic and NMR spectroscopic studies in solution confirmed that these characteristics were retained for solvated molecules, but the operation of concerted anion/ ligand transfers with the larger cations induced subtle structural variations. Combined with the strong red photoluminescence of Eu(Lk)ACHTUNGTRENUNG(hfac)3], the ternary system LnIII/hfac-/Lk is a promising candidate for the planned metalloading of preformed multi-tridentate polymers.

Bost, N., Westall, F., Gaillard, F., Ramboz, C. and Foucher, F.

Synthesis of a spinifex-textured basalt as an analog to Gusev crater basalts, Mars

Meteoritics & Planetary Science (2012) sous presse – doi:10.1111/j.1945-5100.2012.01355.x

Résumé :

Analyses by the Mars Exploration Rover (MER), Spirit, of Martian basalts from Gusev crater show that they are chemically very different from terrestrial basalts, being characterized in particular by high Mg- and Fe-contents. To provide suitable analog basalts for the International Space Analogue Rockstore (ISAR), a collection of analog rocks and minerals for preparing in situ space missions, especially, the upcoming Mars mission MSL-2011 and the future international Mars-2018 mission, it is necessary to synthesize Martian basalts. The aim of this study was therefore to synthesize Martian basalt analogs to the Gusev crater basalts, based on the geochemical data from the MER rover Spirit. We present the results of two experiments, one producing a quench-cooled basalt (<1 h) and one producing a more slowly cooled basalt (1 day). Pyroxene and olivine textures produced in the more slowly cooled basalt were surprisingly similar to spinifex textures in komatiites, a volcanic rock type very common on the early Earth. These kinds of ultramafic rocks and their associated alteration products may have important astrobiological implications when associated with aqueous environments. Such rocks could provide habitats for chemolithotrophic microorganisms, while the glass and phyllosilicate derivatives can fix organic compounds.

Beaufour, M., Godin, F., Vallée, B., Cadène, M. and Bénédetti, H.

Interaction proteomics suggests a new role for the Tfs1 protein in yeast

Journal of Proteome Research (sous presse) doi : 10.1021/pr201239t

Résumé :

The PEBP (phosphatidylethanolamine-binding protein) family is a large group of proteins whose human member, hPEBP1, has been shown to play multiple functions, influencing intracellular signaling cascades, cell cycle regulation, neurodegenerative processes, and reproduction. It also acts, by an unknown mechanism, as a metastasis suppressor in a number of cancers. A more complete understanding of its biological role is thus necessary. As the yeast Saccharomyces cerevisiae is a powerful and easy to handle model organism, we focused on Tfs1p, the yeast ortholog of hPEBP1. In a previous study based on a two-hybrid approach, we showed that Tfs1p interacts and inhibits Ira2p, a GTPase Activating Protein (GAP) of the small GTPase Ras. In order to further characterize the molecular functions of Tfs1p, we undertook the identification of protein complexes formed around Tfs1p using a targeted proteomics approach. Complexed proteins were purified by tandem-affinity, cleaved with trypsin, and identified by nanoflow liquid chromatography coupled with tandem mass spectrometry. Overall, 14 new interactors were identified, including several proteins involved in intermediate metabolism. We confirmed by co-immunoprecipitation that Tfs1p interacts with Glo3p, a GAP for Arf GTPases belonging to the Ras superfamily of small GTPases, indicating that Tfs1p may be involved in the regulation of another GAP. We similarly confirmed the binding of Tfs1p with the metabolic enzymes Idp1p and Pro1p. Integration of these results with known functional partners of Tfs1p shows that two subnetworks meet through the Tfs1p node, suggesting that it may act as a bridge between cell signaling and intermediate metabolism in yeast.

Vandamme, M., Robert, E., Lerondel, S., Sarron, V., Ries, D., Dozias, S., Sobilo, J., Gosset, D., Kieda, C., Legrain, B., Pouvesle, J.M., and Le Pape, A.

ROS implication in a new antitumor strategy based on non-thermal plasma

International Journal of Cancer 130 (9) 2185-2194

Résumé :

Non-thermal plasma (NTP) is generated by ionizing neutral gas molecules/atoms leading to a highly reactive gas at ambient temperature containing excited molecules, reactive species and generating transient electric fields. Given its potential to interact with tissue or cells without a significant temperature increase, NTP appears as a promising approach for the treatment of various diseases including cancer. The aim of our study was to evaluate the interest of NTP both in vitro and in vivo. To this end, we evaluated the antitumor activity of NTP in vitro on two human cancer cell lines (glioblastoma U87MG and colorectal carcinoma HCT-116). Our data showed that NTP generated a large amount of reactive oxygen species (ROS), leading to the formation of DNA damages. This resulted in a multiphase cell cycle arrest and a subsequent apoptosis induction. In addition, in vivo experiments on U87MG bearing mice showed that NTP induced a reduction of bioluminescence and tumor volume as compared to nontreated mice. An induction of apoptosis was also observed together with an accumulation of cells in S phase of the cell cycle suggesting an arrest of tumor proliferation. In conclusion, we demonstrated here that the potential of NTP to generate ROS renders this strategy particularly promising in the context of tumor treatment.

Collet, G., Skrzypek, K., Grillon, C., Matejuka, A., El Hafni-Rahbia, B., Lamerant-Fayel, N. and Kieda, C.

Hypoxia control to normalize pathologic angiogenesis: potential role for endothelial precursor cells and miRNAs regulation

Vascular Pharmacology (sous presse) doi: 10.1016/j.vph.2012.03.001

Résumé :

Hypoxia, a critical parameter of the tumor microenvironment, controls endothelial/tumor cell interactions and is the key to tumor angiogenesis development. Under hypoxic stress, tumor cells produce factors that promote angiogenesis, vasculogenesis, tumor cell motility, metastasis and cancer stem cell selection.

Targeting tumor vessels is a therapeutic strategy that has lately been fast evolving from antiangiogenesis to vessel normalization as discussed in this review. We shall focus on the pivotal role of endothelial cells within the tumor microenvironment, the specific features and the part played by circulating endothelial precursors cells. Attention is stressed on their recruitment to the tumor site and their role in tumor angiogenesis where they are submitted to miRNAs-mediated de/regulation. Here the compensation of the tumor deregulated angiogenic miRNAs – angiomiRs – is emphasized as a potential therapeutic approach. The strategy is to over express anti-angiomiRs in the tumor angiogenesis site upon selective delivery by precursor endothelial cells as miRs carriers.