DE L'ARTIFICIALISME AU SURREALISME (STYRSKY ET TOYEN, 1926-1934.)

LES PEINTRES J.STYRSKY (1899-1942) ET TOYEN (1902-1980) SONT DES FIGURES ESSENTIELLES DE L'AVENEMENT DU SURREALISME A PRAGUE. LE STYLE ARTIFICIALISTE, ENTRE FIGURATION ET ABSTRACTION, QU'ILS CREENT EN 1926 LORS DE LEUR SEJOUR PARISIEN, COMPORTENT DEJA DES SIGNES D'AFFINITES AVEC CETTE ORIENTATION FUTURE. TOYEN ELABORE DES ESPACES FLUIDES OU LA LIQUIDITE, SURGIE DES COMPOSITIONS COMME DES TECHNIQUES, EVOQUE L'IMMERSION DANS LA MATIERE COMME ON PLONGE AU FOND DE SOI-MEME. L'ESPACE ECLATE DE STYRSKY, PROFONDEMENT LIE A SA VISION DU MONDE S'ALLIE PEU A PEU A DES PROCESSUS DELETERES ET DEVIENT REVELATEUR DES PULSIONS DE MORT A L'OEUVRE DANS LA PEINTURE. LA DISTANCE QU'ILS MAINTIENNENT AVEC LE SURREALISME EST EN PARTIE LIEE A DES RESISTANCES A L'EGARD DE L'AUTOMATISME PSYCHIQUE QUI LEUR SEMBLE INCOMPATIBLE AVEC UNE PRATIQUE QUI MET L'ACCENT SUR LE GESTE, LA TECHNIQUE, LA MATIERE ET LA COULEUR. CEPENDANT, LEUR INTERET POUR LE REVE ET L'EROTISME CONSTITUENT DEUX CHAMPS OUVERTS SUR L'INCONSCIENT A TRAVERS LESQUELS ILS SE FRAIENT UN CHEMIN VERS LE SURREALISME. LES RECITS DE REVE DE STYRSKY APPARAISSENT COMME UN MATERIEL ESSENTIEL QUANT A LA COMPREHENSION DE SON OEUVRE ET PRESENTENT LES MEMES SIGNES QUE SON OEUVRE PLASTIQUE OU SES POEMES. LES PRODUCTIONS POETIQUES DE STYRSKY SONT MOINS SOUMISES A LA PREMEDITATION QUE SES TABLEAUX ; CONSTRUITES SUR DES ASSOCIATIONS LIBRES, ELLES PRENNENT UN ASPECT ENIGMATIQUE CARACTERISTIQUE DES TEXTES SURREALISTES. ENFIN, AVEC LES TEXTES POETIQUES EN PROSE DU DEBUT DES ANNEES TRENTE QUI CELEBRENT LE DESIR ET LA FEMME AIMEE, STYRSKY DEVELOPPE UNE THEMATIQUE PRIVILEGIEE DU SURREALISME. LA PEINTURE DE TOYEN EVOLUE VERS UN TRAVAIL SUR UNE MATIERE PLUS DENSE. ELLE DEVELOPPE DES IMAGES NOCTURNES, LIEUX FAVORABLES AU BROUILLAGE DES REPERES. COMME LE VIDE ET LA COUPURE SERVENT DE TOILE DE FOND AUX REVES DE STYRSKY, LE CREUX ET LA FISSURE DEVIENNENT LE THEATRE DES VISIONS ONIRIQUES DE TOYEN ET CONTIENNENT UNE DIMENSION EROTIQUE MANIFESTE. L'EVOLUTION DE LA PEINTURE DE TOYEN ET STYRSKY PASSE PAR UN ABANDON DES STRUCTURES PLANES DE L'ARTIFICIALISME POUR DES IMAGES PLUS REALISTES ET ILLUSIONNISTES ET D'AUTRES ARTISTES AUTOUR D'EUX SUIVENT LE MEME CHEMIN MAIS ILS N'ADHERERONT PAS AU SURREALISME. TOYEN ET STYRSKY SERONT LES SEULS PEINTRES DU GROUPE FONDE A PRAGUE EN 1934.PARIS1-BU Pierre Mendès-France (751132102) / SudocPARIS-INHA (751025206) / SudocSudocFranceF

Etude structurale et dynamique par résonance magnétique nucléaire, d'une protéine de transfert de lipides isolée dans le tabac

La LTP1 extraite de feuille de Nicotiana tabacum, nommée LTP1_1, a été produite dans Pichia pastoris. Nous avons ainsi déterminer sa structure tridimensionnelle par RMN 2D, 3D et modélisation moléculaire. Différentes études d'interaction et de dynamique ont ensuite mis en évidence des propriétés de fixation particulières comparativement aux autres LTPs. Ces travaux ont servi de base à la détermination de structures d'autres LTP1 de tabac par modélisation comparative et à des simulations de dynamique moléculaire à température ambiante et à haute température. De plus, nous avons cartographié la cavité hydrophobe de la LTP1_1 en utilisant la RMN du xénon hyperpolarisé. L'ensemble de ces travaux a permis d'identifier les acides aminés impliqués spécifiquement dans la fixation des lipides. Nous avons découvert que les propriétés remarquables de fixation des LTP1 sont liées non seulement à leur structure originale mais également à leur dynamique particulière.ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

The solution structure of gomesin, an antimicrobial cysteine-rich peptide from the spider.

Gomesin is the first peptide isolated from spider exhibiting antimicrobial activities. This highly cationic peptide is composed of 18 amino-acid residues including four cysteines forming two disulfide linkages. The solution structure of gomesin has been determined using proton two-dimensional NMR (2D-NMR) and restrained molecular dynamics calculations. The global fold of gomesin consists in a well-resolved two-stranded antiparallel betasheet connected by a noncanonical betaturn. A comparison between the structures of gomesin and protegrin-1 from porcine and androctonin from scorpion outlines several common features in the distribution of hydrophobic and hydrophilic residues. The N- and C-termini, the betaturn and one face of the betasheet are hydrophilic, but the hydrophobicity of the other face depends on the peptide. The similarities suggest that the molecules interact with membranes in an analogous manner. The importance of the intramolecular disulfide bridges in the biological activity of gomesin is being investigated

The active site of drosomycin, a small insect antifungal protein, delineated by comparison with the modeled structure of Rs-AFP2, a plant antifungal protein

Drosomycin is the first strictly antifungal protein isolated from an insect (Drosophila melanogaster). The solution structure of this 44-residue protein has been reported previously. It involves a three-stranded β-sheet and an α-helix, the protein global fold being maintained by four disulfide bridges. Rs-AFP2 is a plant antifungal protein exhibiting 41% sequence similarity with drosomycin. Mutational analysis of Rs-AFP2 showed the importance of some residues in the antifungal activity of the protein against the fungus target. In order to determine the structural features responsible for antifungal activity in both drosomycin and Rs-AFP2, we modeled the three-dimensional structure of Rs-AFP2, and of other antifungal proteins, using the solution structure of drosomycin as a template. Structure analysis of drosomycin and Rs-AFP2, and comparisons with the other modeled antifungal structures, revealed that the two proteins shared a hydrophobic cluster located at the protein surface in which a lysine residue is embedded. Based on these close structural similarities and the experimental data available for Rs-AFP2 mutants, an antifungal active site of the insect protein is proposed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Rational design of peptides active against the Gram positive bacteria Staphylococcus aureus

n an attempt to increase the antimicrobial activity of the insect defensin from Anopheles gambiae, which is active against Staphylococcus aureus at low concentration, hybrid defensins were designed by combining conserved sequence regions and variable regions of insect defensins. Their activity against S. aureus strains sensitive and resistant to conventional antibiotics was evaluated, and the toxicity of the most active molecules was tested. The three-dimensional structure of Anopheles gambiae defensin and five hybrids were determined by NMR and molecular modelling. This strategy led to the design of two chimeric defensins with increased activity compared with the native molecule, but one of them appears to be toxic to mice at a rather low concentration. The structure of the CS motif, which is a characteristic of insect defensin, is sensitive to sequence modifications, in particular in the N-terminal loop. The existence of the CS is most probably a prerequisite for the stability and the activity of the molecule, but is not sufficient by itself since the hybrid displaying the best defined structure is not active against the tested strains. The analysis of the structure, in relation with the activity and the toxicity data, underlines the importance of turns and of the N-terminal loop. Residues located in the turns contributing to the preservation of positive electrostatic areas at the surface of the molecules seem particularly important for the activity of the molecule, while residues involved in the N-terminal loop are both involved in the modulation of the activity and the toxicity of the molecule

Solution structures of stomoxyn and spinigerin, two insect antimicrobial peptides with an alpha-helical conformation

Stomoxyn and spinigerin belong to the class of linear cysteine-free insect antimicrobial peptides that kill a range of microorganisms, parasites, and some viruses but without any lytic activity against mammalian erythrocytes. Stomoxyn is localized in the gut epithelium of the nonvector stable fly that is sympatric with the trypanosome vector tsetse fly. Spinigerin is stored and secreted by hemocytes from the fungus-growing termite. The structure of synthetic stomoxyn and spinigerin in aqueous solution and in TFE/water mixtures was analyzed by CD and NMR spectroscopy combined with molecular modeling calculations. Stomoxyn and spinigerin adopt a flexible random coil structure in water while both assume a stable helical structure in the presence of TFE. In 50% TFE, the structure of stomoxyn is typical of cecropins, including an amphipathic helix at the N-terminus and a hydrophobic C-terminus with helical features that probably fold in a helical conformation at higher TFE concentration. In contrast to stomoxyn, spinigerin acquires very rapidly a helical conformation. In 10% TFE the helix is highly bent and the structure is poorly defined. In 50% TFE, the helical structure is well defined all along its sequence, and the slightly bent -helix displays an amphiphilic character, as observed for magainin 2. The structural similarities between stomoxyn and cecropin A from Hyalophora cecropia and between spinigerin and magainin 2 suggest a similar mode of action on the bacterial membranes of both pairs of peptides. Our results also confirm that TFE induces helix formation and propagation for amino acids showing helical propensity in water but also enhances the helix propagation propensity of nonpolar -branched residues

Solvation study of the non-specific lipid transfer protein from wheat by intermolecular NOEs with water and small organic molecules

International audienceIntermolecular nuclear Overhauser effects (NOEs) were measured between the protons of various small solvent or gas molecules and the non-specific lipid transfer protein (ns-LTP) from wheat. Intermolecular NOEs were observed with the hydrophobic pocket in the interior of wheat ns-LTP, which grew in intensity in the order cyclopropane (saturated solution) < methane (140 bar) < ethane (40 bar) < acetonitrile (5% in water) < cyclohexane (saturated solution) < benzene (saturated solution). No intermolecular NOEs were observed with dioxane (5% in water). The intermolecular NOEs were negative for all of the organic molecules tested. Intermolecular NOEs between wheat ns-LTP and water were weak or could not be distinguished from exchange-relayed NOEs. As illustrated by the NOEs with cyclohexane versus dioxane, the hydrophobic pocket in wheat ns-LTP preferably binds non-polar molecules. Yet, polar molecules like acetonitrile can also be accommodated. The pressure dependence of the NOEs between methane and wheat ns-LTP indicated incomplete occupancy, even at 190 bar methane pressure. In general, NOE intensities increased with the size of the ligand molecule and its vapor pressure. NMR of the vapor phase showed excellent resolution between the signals from the gas phase and those from the liquid phase. The vapor concentration of cyclohexane was fivefold higher than that of the dioxane solution, supporting the binding of cyclohexane versus uptake of dioxane