Journals
2009 EN
Annaleise R. HowardJones · Virgile Adam · A.R. Cowley
+2 more
Mechanistic investigations of biological enzymatic processes require controlled initiation and monitoring of catalytic reactions. A well-known technique to trap and observe reaction intermediates building up along a reaction pathway is the use of low temperature conditions. Here, we report a kinetically competent system for the release of molecular oxygen at cryogenic temperature, using a cobalt-based caged oxygen molecule, (micro-peroxo)(micro-hydroxo)bis[bis(bipyridyl)cobalt(III)] nitrate. Cryophotolysis of this compound was induced using 266 nm laser light and monitored by absorption microspectrophotometry. Furthermore, to verify that photo-fragmentation was accompanied by release of the active caged molecule, the production of dioxygen during cryophotolysis was directly visualized. This work lays the foundations for the use of low temperature reaction triggering as a tool to prolong the lifetime of normally unstable intermediate states in oxygen-dependent enzymes.
Springer Science+Business Media
Journals
2009 EN
Jeralyn D. Haraldsen · Gu Liu · Catherine H. Botting
+9 more
Conoidin A (1) is an inhibitor of host cell invasion by the protozoan parasite Toxoplasma gondii. In the course of studies aimed at identifying potential targets of this compound, we determined that it binds to the T. gondii enzyme peroxiredoxin II (TgPrxII). Peroxiredoxins are a widely conserved family of enzymes that function in antioxidant defense and signal transduction, and changes in PrxII expression are associated with a variety of human diseases, including cancer. Disruption of the TgPrxII gene by homologous recombination had no effect on the sensitivity of the parasites to 1, suggesting that TgPrxII is not the invasion-relevant target of 1. However, we showed that 1 binds covalently to the peroxidatic cysteine of TgPrxII, inhibiting its enzymatic activity in vitro. Studies with human epithelial cells showed that 1 also inhibits hyperoxidation of human PrxII. These data identify Conoidin A as a novel inhibitor of this important class of antioxidant and redox signaling enzymes.
Royal Society of Chemistry
Journals
2009 EN
Michael Klein · Peter Dinér · Dominique DorinSemblat
+2 more
Efficient routes to 3-(1,2,3-triazol-1-yl)- and 3-(1,2,3-triazol-4-yl)pyrazolo[3,4-d]pyrimidin-4-amines using a one-pot two-step reaction are presented. The two routes give easy access to two different isomers of 1,4-disubstituted triazoles and the target compounds are obtained from a variety of readily available aromatic and aliphatic halides without isolation of potentially unstable organic azide intermediates. Two compounds show activity towards the PfPK7 kinase (IC(50) 10-20 microM) of P. falciparum, the organism responsible for the most virulent form of malaria, and can be regarded as hits useful for further development into lead compounds.
Royal Society of Chemistry
Journals
2009 EN
Blandine Maître · Catherine Angénieux · Virginie Wurtz
+13 more
CD1e displays unique features in comparison with other CD1 proteins. CD1e accumulates in Golgi compartments of immature dendritic cells and is transported directly to lysosomes, where it is cleaved into a soluble form. In these latter compartments, CD1e participates in the processing of glycolipid antigens. In the present study, we show that the N-terminal end of the membrane-associated molecule begins at amino acid 20, whereas the soluble molecule consists of amino acids 32-333. Thus immature CD1e includes an N-terminal propeptide which is cleaved in acidic compartments and so is absent from its mature endosomal form. Mutagenesis experiments demonstrated that the propeptide controls the assembly of the CD1e alpha-chain with beta(2)-microglobulin, whereas propeptide-deleted CD1e molecules are immunologically active. Comparison of CD1e cDNAs from different mammalian species indicates that the CD1e propeptide is conserved during evolution, suggesting that it may also optimize the generation of CD1e molecules in other species.
Conference Proceedings
2009 EN
Nasir Mahmood Abbasi · Salil Gunashekar · E.M. Warrington
+5 more
Multiple input multiple output (MIMO) systems utilize multiple antennas at both the transmitter and the receiver. This paper describes some recent experimental work that has been carried out in order to investigate the feasibility of applying MIMO techniques within the high frequency (HF) band. It is a significant development because the potential increase in data rates will benefit not only the existing HF radio systems but also open this band to new low cost communication applications. The capacity estimates for systems employing multiple antennas at the transmitter and receiver in the HF band are computed. Specifically a comparison is made between MIMO configurations employing homogenous antenna arrays and collocated antenna arrays in terms of their envelope correlation and capacity. The results indicate that the HF band can be used for MIMO applications and that compact collocated antennas can replace large homogenous arrays to provide potential capacity gains.
Journals
2009 EN
Romain Teyssier · Sandrine Pires · Simon Prunet
+7 more
We have performed a 70 billion dark-matter particles N-body simulation in a 2$h^{-1}$ Gpc periodic box, using the concordance, cosmological model as favoredby the latest WMAP3 results. We have computed a full-sky convergence map with aresolution of $\Delta \theta \simeq 0.74$ arcmin$^{2}$, spanning 4 orders ofmagnitude in angular dynamical range. Using various high-order statistics on arealistic cut sky, we have characterized the transition from the linear to thenonlinear regime at $\ell \simeq 1000$ and shown that realistic galacticmasking affects high-order moments only below $\ell < 200$. Each domain(Gaussian and non-Gaussian) spans 2 decades in angular scale. This map istherefore an ideal tool for testing map-making algorithms on the sphere. As afirst step in addressing the full map reconstruction problem, we havebenchmarked in this paper two denoising methods: 1) Wiener filtering applied tothe Spherical Harmonics decomposition of the map and 2) a new method, calledMRLens, based on the modification of the Maximum Entropy Method on a Waveletdecomposition. While the latter is optimal on large spatial scales, where thesignal is Gaussian, MRLens outperforms the Wiener method on small spatialscales, where the signal is highly non-Gaussian. The simulated full-skyconvergence map is freely available to the community to help the development ofnew map-making algorithms dedicated to the next generation of weak-lensingsurveys.
Journals
2009 EN
Christoph Mordasini · Yann Alibert · Willy Benz
+1 more
This is the second paper in a series of papers showing the results ofextrasolar planet population synthesis calculations. In the companion paper(Paper I), we have presented in detail our methods. By applying anobservational detection bias for radial velocity surveys, we identify thepotentially detectable synthetic planets. The properties of these planets arecompared in quantitative statistical tests with the properties of a carefullyselected sub-population of actual exoplanets. We use a two dimensionalKolmogorov-Smirnov test to compare the mass-distance distributions of syntheticand observed planets, as well as 1D KS tests to compare the mass, the semimajoraxis and the [Fe/H] distributions. We find that some models can account to areasonable degree of significance for the observed properties. We concurrentlyaccount for many other observed features, e.g. the "metallicity effect". Thisgives us confidence that our model captures several essential features of giantplanet formation. Our simulations allow us also to extract the properties ofthe underlying exoplanet population that are not yet detectable. For example,we have derived the planetary initial mass function (PIMF) and have been led toconclude that the planets detected so far represent only the tip of theiceberg. The PIMF can also be used to predict how the detectable extrasolarplanet population will change as the precision of radial velocity surveysimproves to an extreme precision of 0.1 m/s.
Journals
2009 EN
LERMA Maryvonne Gerin · LAM-CAB Nuria Marcelino · LESIA Nicolas Biver
+5 more
Ammonia is one of the best tracers of cold dense cores. It is also a minorconstituent of interstellar ices and, as such, one of the important nitrogenreservoirs in the protosolar nebula, together with the gas phase nitrogen, inthe form of N2 and N. An important diagnostic of the various nitrogen sourcesand reservoirs of nitrogen in the Solar System is the 14N/15N isotopic ratio.While good data exist for the Solar System, corresponding measurements in theinterstellar medium are scarce and of low quality. Following the successfuldetection of the singly, doubly, and triply deuterated isotopologues ofammonia, we have searched for 15NH2D in dense cores, as a new tool forinvestigating the 14N/15N ratio in dense molecular gas. With the IRAM-30mtelescope, we have obtained deep integrations of the ortho 15NH2D(1(1,1)-1(0,1)) line at 86.4 GHz, simultaneously with the corresponding orthoNH2D line at 85.9 GHz. o-15NH2D is detected in Barnard-1b, NGC1333-DCO+, andL1689N, while we obtained upper limits towards LDN1544 and NGC1333-IRAS4A, anda tentative detection towards L134N(S). The 14N/15N abundance ratio in NH2Dranges between 350 and 850, similar to the protosolar value of ~ 424, andlikely higher than the terrestrial ratio of 270.
Journals
2009 EN
D. Mourard · J. M. Clausse · A. Marcotto
+30 more
International audienceContext: Among optical stellar interferometers, the CHARA Array located at Mt Wilson in California offers the potential of very long baselines (up to 330 m) and the prospect of coupling multiple beam combiners. This paper presents the principle and the measured performance of VEGA, Visible spEctroGraph and polArimeter installed in September 2007 at the coherent focus of the array. Aims: With 0.3 ms of arc of spatial resolution and up to 30 000 of spectral resolution, VEGA intends to measure fundamental parameters of stars, to study stellar activities and to image and analyze circumstellar environments. We describe the observing modes that have been implemented for this spectro-polarimeter and show actual performances measured on the sky during the first observing runs. Methods: The astrophysical programs are described in relation to the observing modes of the instrument, the presentation of the spectrograph and of the interface table is shown and finally the data is presented. We discuss the perspectives of further development in the framework of the CHARA Array. Results: We show that VEGA/CHARA is fully operational. The current limiting magnitude is nearly 7 but the results depend on the observing conditions (seeing, spectral resolution, etc.). We have validated the stability of the instrumental visibility at the level of 1 to 2% over half an hour and of the instrumental polarization for various declinations. Some examples of squared visibility and differential visibility are presented. Conclusions: The spectro-polarimeter VEGA has been installed and successfully tested on CHARA. It will permit stellar physics studies at unprecedented spectral and spatial resolutions
Journals
2009 EN
A. BenMoussa · I. E. Dammasch · J.F. Hochedez
+18 more
Aims. LYRA, the Large Yield Radiometer, is a vacuum ultraviolet (VUV) solar radiometer, planned to be launched in November 2009 on the European Space Agency PROBA2, the Project for On-Board Autonomy spacecraft. Methods. The instrument was radiometrically calibrated in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the Berlin Electron Storage ring for SYnchroton radiation (BESSY II). The calibration was done using monochromatized synchrotron radiation at PTB's VUV and soft X-ray radiometry beamlines using reference detectors calibrated with the help of an electrical substitution radiometer as the primary detector standard. Results. A total relative uncertainty of the radiometric calibration of the LYRA instrument between 1% and 11% was achieved. LYRA will provide irradiance data of the Sun in four UV passbands and with high temporal resolution down to 10 ms. The present state of the LYRA pre-flight calibration is presented as well as the expected instrument performance.