386 research outputs found
Description de la femelle de Drusus spelaeus (Ulmer) [Trich.Limnophilidae]
No full textBouvet Yvette, Gautheron-Duranthon F. Description de la femelle de Drusus spelaeus (Ulmer) [Trich.Limnophilidae]. In: Bulletin de la Société entomologique de France, volume 75 (7-8), Septembre-octobre 1970. pp. 199-201
The COMPASS polarized target
No full textGautheron F, Baum G, Kisselev Y, et al. The COMPASS polarized target. In: 16th Intern. Spin Physics Symposium and Workshop on Polarized Electron Sources and Polarimeters. Trieste; 2004: 791-795
Large-scale purification and characterization of the five subunits of F1-ATPase from pig heart mitochondria.
No full textInternational audienceA large-scale purification procedure was developed to isolate the five subunits of F1-ATPase from pig heart mitochondria. The previously described procedure (Williams, N. and Pedersen, P.L. (1986) Methods Enzymol. 126, 484-489) to dissociate the rat liver F1-ATPase by cold treatment followed by warming at 37 degrees C has been adapted for the pig heart enzyme. Removal of endogenous nucleotides from that enzyme before dissociation led to the efficient separation of the alpha and gamma subunits from beta, delta and epsilon subunits. The beta subunit was purified in the hundred-milligram range by anion-exchange chromatography in the absence of any denaturing agent. This subunit was free from any bound nucleotide and almost no ATPase and adenylate kinase-like activities were detected. The delta and epsilon subunits were purified by reversed-phase chromatography (RP-HPLC) in the milligram range. As recently reported (Penin, F., Deleage, G., Gagliardi, D., Roux, B. and Gautheron, D.C. (1990) Biochemistry 29, 9358-9364), these purified subunits kept biophysical features of folded proteins and their ability to reconstitute the tight delta epsilon complex. The alpha and gamma subunits remained poorly soluble and required dissociation by 8 M guanidinium chloride prior to their purification by RP-HPLC. In addition, characterizations of the five subunits by IEF and SDS-polyacrylamide gel electrophoresis are reported, as well as ultraviolet spectra and solubility properties of the beta, delta and epsilon subunits.A large-scale purification procedure was developed to isolate the five subunits of F1-ATPase from pig heart mitochondria. The previously described procedure (Williams, N. and Pedersen, P.L. (1986) Methods Enzymol. 126, 484-489) to dissociate the rat liver F1-ATPase by cold treatment followed by warming at 37 degrees C has been adapted for the pig heart enzyme. Removal of endogenous nucleotides from that enzyme before dissociation led to the efficient separation of the alpha and gamma subunits from beta, delta and epsilon subunits. The beta subunit was purified in the hundred-milligram range by anion-exchange chromatography in the absence of any denaturing agent. This subunit was free from any bound nucleotide and almost no ATPase and adenylate kinase-like activities were detected. The delta and epsilon subunits were purified by reversed-phase chromatography (RP-HPLC) in the milligram range. As recently reported (Penin, F., Deleage, G., Gagliardi, D., Roux, B. and Gautheron, D.C. (1990) Biochemistry 29, 9358-9364), these purified subunits kept biophysical features of folded proteins and their ability to reconstitute the tight delta epsilon complex. The alpha and gamma subunits remained poorly soluble and required dissociation by 8 M guanidinium chloride prior to their purification by RP-HPLC. In addition, characterizations of the five subunits by IEF and SDS-polyacrylamide gel electrophoresis are reported, as well as ultraviolet spectra and solubility properties of the beta, delta and epsilon subunits
A new calibration of radiation damage control on He diffusivity in apatite: implications for (U-Th)/He thermochronology
No full textInternational audienceIn low temperature thermochronology, reliable interpretation of (U-Th)/He data is controlled by our understanding of helium diffusion in a crystal. The diffusion kinetics can be simulated through the classic Arrhenius-type equation, with parameters frequency factor Do and activation energy Ea (Farley, 2000). For apatite, it has been demonstrated that accumulated radiation damage perturbed the Arrhenius-type equation and exerts a strong control on He diffusion. Two models have been developed to parameterise the evolution of diffusion kinetics in apatite in terms of accumulated radiation damage: one based on the physical phenomenon (Gautheron et al., 2009) and the other calibrated on empirical observations (Flowers et al., 2009). As the amount of radiation damage depends on both time (U and Th decay producing damage) and temperature (annealing of radiation damage), both of these models are routinely used to interpret apatite (U-Th)/He data in terms of thermal histories. However, results obtained from inverse thermal history modelling with these two models can differ and be inconsistent with other low thermochronological data (e.g., apatite fission tracks). In this contribution we present a new radiation damage-based diffusion model that combines the approaches of both the Gautheron et al. and Flowers et al. models.Our new model is based on the theoretical diffusion model proposed by Gerin et al. (2017) but incorporates a new calibration from the available He diffusion experiment results. The Gerin et al. model is built on a theoretical understanding of the fundamental physical processes and predicts diffusion parameters for different levels of crystal lattice damage, using quantum calculus. We recalibrated this model through an empirical law based on real crystal mesh damage calculated from available experimental data. To test the reliability of the revised model and to compare it to the existing models, it was implemented in the modelling software, QTQt (Gallagher, 2012). Here we present results of both forward and inverse modelling to highlight the benefits of the new model. The results are assessed in terms of the impact for “deep time” (>500 Ma) thermochronology, in which accumulated radiation damage can have a significant control on the inferred thermal history models.Farley, K.A., 2000. Helium diffusion from apatite: General behavior as illustrated by Durango fluorapatite. J. Geophys. Res. 105, 2903–2914. https://doi.org/10.1029/1999JB900348Flowers, R.M., Ketcham, R.A., Shuster, D.L., Farley, K.A., 2009. Apatite (U–Th)/He thermochronometry using a radiation damage accumulation and annealing model. Geochimica et Cosmochimica Acta 73, 2347–2365. https://doi.org/10.1016/j.gca.2009.01.015Gallagher, K., 2012. Transdimensional inverse thermal history modeling for quantitative thermochronology. Journal of Geophysical Research: Solid Earth 117, n/a-n/a. https://doi.org/10.1029/2011JB008825Gautheron, C., Tassan-Got, L., Barbarand, J., Pagel, M., 2009. Effect of alpha-damage annealing on apatite (U–Th)/He thermochronology. Chemical Geology 266, 157–170. https://doi.org/10.1016/j.chemgeo.2009.06.001Gerin, C., Gautheron, C., Oliviero, E., Bachelet, C., Mbongo Djimbi, D., Seydoux-Guillaume, A.-M., Tassan-Got, L., Sarda, P., Roques, J., Garrido, F., 2017. Influence of vacancy damage on He diffusion in apatite, investigated at atomic to mineralogical scales. Geochimica et Cosmochimica Acta 197, 87–103. https://doi.org/10.1016/j.gca.2016.10.01
Crystal data for bis(η<sup>5</sup>-<i>tert</i>-butylcyclopentadienyl)hafnium(IV) dihydride dimer, [(η<sup>5</sup>-<i>t</i>-BuC<sub>5</sub>H<sub>4</sub>)<sub>2</sub>HfH(μ-H)]<sub>2</sub>
No full textThe air-sensitive title hydride [Hf(C9H13)2H2]2 was prepared by hydrogenolysis of (t-BuCp)2HfMe2 [Couturier, Tainturier & Gautheron (1980). J. Organomet. Chem.
195, 291–306] and crystallized from a solution in heptane or toluene and hexane. The compound is triclinic with the following cell parameters: a = 7.22(3), b = 10.31(4), c = 12.47(6) Å, α = 80.4(4), β = 74.6(4)°, γ = 72.1(3)°, V = 847 Å3, Z = 1, Dx
= 1.67 Mg m− 3. Powder diffraction data were obtained from Debye–Scherrer photographs. The extended version of the paper examines several examples where Zr or Hf hydrides are monomers or dimers and shows that this structure is very similar to the related [(MeCp)2ZrH2]2 compound [Jones & Petersen (1981). Inorg. Chem.
20, 2889–2894]. This similarity and spectroscopic data show that the molecule probably has a center of symmetry situated between the two Hf atoms and the two bridging H atoms. The JCPDS Diffraction File No. for [Hf(C9H13)2H2]2 is 33-1996. </jats:p
Role of phosphate on the ADP-induced hysteretic inhibition of mitochondrial adenosine 5'-triphosphatase. Effects of the natural protein inhibitor.
No full textInternational audiencePreincubation of F1-ATPase with ADP and Mg2+ leads to ADP binding at regulatory site inducing a hysteretic inhibition of ATP hydrolysis, i.e., an inhibition that slowly develops after Mg-ATP addition (Di Pietro, A., Penin, F., Godinot, C. and Gautheron, D.C. (1980) Biochemistry 19, 5671-5678). It is shown here that inorganic phosphate (Pi) together with ADP during preincubation abolishes the time-dependence of the inhibition after the addition of the substrate Mg-ATP. This preincubation in the presence of both Pi and ADP slowly leads to a conformation of the enzyme immediately inhibited after the addition of the substrate Mg-ATP. The Pi effect is half-maximal at 35 microM and pH 6.6, whereas a limited effect is induced at pH 8.0. The preincubation of F1-ATPase with Pi and ADP must last long enough (t1/2 = 5 min). The effects can be correlated to the amount of Pi bound to the enzyme, 1 mol Pi per mol (apparent KD of 33 microM) at saturation. Pi neither modifies the ADP binding nor the final level of the concomitant inhibition. When Pi is not present in the preincubation, the final stable rate of ADP-induced hysteretic inhibition is always reached when a near-constant amount of Pi has been generated during Mg-ATP hydrolysis. Kinetic experiments indicate that preincubation with ADP and Pi decreases both Vmax and Km which would favor a conformational change of the enzyme. Taking into account the Pi effects, a more precise model of hysteretic inhibition is proposed. The natural protein inhibitor IF1 efficiently prevents the binding of Pi produced by ATP hydrolysis indicating that the hysteretic inhibition and the IF1-dependent inhibition obey different mechanisms.Preincubation of F1-ATPase with ADP and Mg2+ leads to ADP binding at regulatory site inducing a hysteretic inhibition of ATP hydrolysis, i.e., an inhibition that slowly develops after Mg-ATP addition (Di Pietro, A., Penin, F., Godinot, C. and Gautheron, D.C. (1980) Biochemistry 19, 5671-5678). It is shown here that inorganic phosphate (Pi) together with ADP during preincubation abolishes the time-dependence of the inhibition after the addition of the substrate Mg-ATP. This preincubation in the presence of both Pi and ADP slowly leads to a conformation of the enzyme immediately inhibited after the addition of the substrate Mg-ATP. The Pi effect is half-maximal at 35 microM and pH 6.6, whereas a limited effect is induced at pH 8.0. The preincubation of F1-ATPase with Pi and ADP must last long enough (t1/2 = 5 min). The effects can be correlated to the amount of Pi bound to the enzyme, 1 mol Pi per mol (apparent KD of 33 microM) at saturation. Pi neither modifies the ADP binding nor the final level of the concomitant inhibition. When Pi is not present in the preincubation, the final stable rate of ADP-induced hysteretic inhibition is always reached when a near-constant amount of Pi has been generated during Mg-ATP hydrolysis. Kinetic experiments indicate that preincubation with ADP and Pi decreases both Vmax and Km which would favor a conformational change of the enzyme. Taking into account the Pi effects, a more precise model of hysteretic inhibition is proposed. The natural protein inhibitor IF1 efficiently prevents the binding of Pi produced by ATP hydrolysis indicating that the hysteretic inhibition and the IF1-dependent inhibition obey different mechanisms
Recovery of mutants impaired in pathogenicity after transposition of impala in Fusarium oxysporum f. sp. melonis
No full textCryogenic control system of the large COMPASS polarized target
No full textGautheron F, Ball J, Baum G, et al. Cryogenic control system of the large COMPASS polarized target. In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Nucl.Instrum.Meth. A. Vol 526. Elsevier Science BV; 2004: 147-152.The dilution refrigerator used to cool the large COMPASS polarized target is monitored through a PC running LabVIEW(TM) 6.1 under Windows 2000(TM). About 60 parameters of the target (temperatures, pressures, flow rates) are continuously plotted and checked. They are periodically recorded in an Oracle(TM) database and in a data file. An alarm for every parameter can be individually activated and optionally connected to a GSM (Global System for Mobile Communication) delivery message system. A web server receives and publishes the online status of the target with online tables and graphics on a dedicated COMPASS polarized target information web site. A Siemens programmable logic controller (PLC) powered by an uninterruptable source keeps the cryogenic system safe and stable during the long beam periods by controlling valves and interlocks. This safety feature protects the dilution refrigerator against potential damages in case of power failure. (C) 2004 Elsevier B.V. All rights reserved
Études de cristaux scintillants de tungstate de plomb et de prototypes de calorimètre électromagnétique pour le projet CMS au LHC
No full textThe CMS detector which will be installed on the LHC is equiped with an electromagnetic calorimeter made of about 110.000 lead tungstate crystals (PbWO4) read out by avalanche photodiodes. The choice of such photodetectors with gain is dictated by the low level of light yield from the scintillation and by the presence of a high magnetic field. This thesis reports on the work done on the crystal in order to improve its characteristics in view of the construction for a high performance calorimeter. In this way, a systematic study of the main quality parameters of the crystal (light yield, uniformity of the response, radiation hardness, optical transmission) has been led. In the same time, the analysis of the data taken in high energy beam tests for several prototype matrices has allowed to confirm the performance, expected mainly related to energy and position resolution. This performance is particularly decisive in the Higgs's boson search in the intermediate mass range using the detection of the 2 gammas mode
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