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Accueil > Publications > Recherche par années > Années 1990 > 1999

1999

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Coordination equilibrium - a clue for fast water exchange on potential magnetic resonance imaging contrast agents ?

A temperature-dependent UV-visible spectrophotometric study on [Eu(DO3A)(H2O)(n)] proved the presence of a hydration equilibrium (n = 1,2), strongly shifted towards the bisaqua species [DO3A = 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane]. The thermodynamic parameters and the reaction volume were determined for the equilibrium [Eu(DO3A)(H2O)] + H2O reversible arrow [Eu(DO3A)(H2O)(2)] and the same results were extrapolated for the Gd(III) analogue (Delta H degrees = -12.6kJ mol(-1), Delta S degrees = -25.2J mol(-1) K-1, K-Eu(298) = 7.7 and Delta V degrees = -7.5 cm(3) mol(-1)). The variable-temperature O-17 NMR data on [Gd(DO3A)((HO)-O-2)(n)] were analysed by two approaches : (i) with the Swift-Connick equations (two-site exchange) and (ii) with the Kubo-Sack formalism (three-site exchange).

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Correlated motions analysis from molecular dynamics trajectories : Statistical accuracy on the determination of canonical correlation coefficients

A numerical study of the accuracy on the determination of a unique global canonical correlation coefficient C between two groups of random variables is presented as a function of the number of variables of both groups (n and m, respectively), of the sampling size N and of the actual level of correlation C between the groups. The method used to estimate C has been already described (Briki, F. ; Genest, D. Biophys Chem 1994, 52, 35-43 ; and J Biomol Struct Dynam 1995, 12, 1063-1082), and is implemented in the home made program TECOR. To check the accuracy on the estimation of C for given values of n, m, N, and C, samples of the random variables are synthesized (with known C), then TECOR is used to get an estimated value M of the global canonical coefficient, which is compared to the actual value C.

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Crystal structure of a double-stranded DNA containing a cisplatin interstrand cross-link at 1.63 angstrom resolution : hydration at the platinated site

cis-diamminedichloroplatinum (II) (cisplatin) is a powerful anti-tumor drug whose target is cellular DNA, In the reaction between DNA and cisplatin, covalent intrastrand and interstrand cross-links (ICL) are formed. Two solution structures of the ICL have been published recently. In both models the double-helix is bent and unwound but with significantly different angle values. We solved the crystal structure at 100K of a double-stranded DNA decamer containing a single cisplatin ICL, using the anomalous scattering (MAD) of platinum as a unique source of phase information.

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Crystal structure of human gastric lipase and model of lysosomal acid lipase, two lipolytic enzymes of medical interest

Fat digestion in humans requires not only the classical pancreatic lipase but also gastric lipase, which is stable and active despite the highly acidic stomach environment. We report here the structure of recombinant human gastric lipase at 3.0-Angstrom resolution, the first structure to be described within the mammalian acid lipase family. This globular enzyme (379 residues) consists of a core domain belonging to the a/ß hydrolase-fold family and a "cap" domain, which is analogous to that present in serine carboxypeptidases.

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Crystallization and preliminary X-ray diffraction analysis of the homodimeric form a(2) of the HU protein from Escherichia coli

The homodimeric form a(2) of the Escherichia coli DNA-binding protein HU was crystallized by the hanging-drop vapour-diffusion method using PEG 4000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 31.09, b = 55.34, c = 117.63 Angstrom, and contain one monomer per asymmetric unit. A full diffraction data set was collected to 2.3 Angstrom resolution on a conventional X-ray source. The molecular-replacement method, using the HU crystallographic model from Bacillus stearothermophilus as a starting point, gave a reliable solution for the rotation and translation functions.

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Crystallization and preliminary X-ray diffraction analysis of the homodimericform alpha2 of the HU protein from Escherichia colimonitoring of the in vitro metabolism in locust tissues

The homodimeric form alpha(2) of the Escherichia coli DNA-binding protein HU was crystallized by the hanging-drop vapour-diffusion method using PEG 4000 as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 31.09, b = 55.34, c = 117.63 Angstrom, and contain one monomer per asymmetric unit. A full diffraction data set was collected to 2.3 Angstrom resolution on a conventional X-ray source. The molecular-replacement method, using the HU crystallographic model from Bacillus stearothermophilus as a starting point, gave a reliable solution for the rotation and translation functions.

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Cutting edge : RANTES regulates Fas ligand expression and killing by HIV-specific CD8 cytotoxic T cells

Based on the previous observation that RANTES mediates the cytotoxic activity of human HIV-specific CD8(+) T cells via the chemokine receptor CCR3, we studied the effect of this chemokine on different effector CD8(+) cytolytic cells requiring Fas/Fas ligand (FasL) or perforin-dependent pathway,In CTLs derived from PBMCs of HIV-infected patients, both the spontaneous and the RANTES-induced cytotoxicity were inhibited by anti-FasL, neutralizing Abs, In contrast, allogeneic CTLs or NK cells killing through perforin were not affected by RANTES and anti-Fast Ab, Accordingly, RANTES enhanced the expression of Fast in a concentration- and time-dependent manner in HIV-specific CTLs, whereas anti-RANTES Ab decreased markedly Fast expression. Finally, cell surface expression of Fast protein in HIV-specific CTLs was also upregulated by eotaxin, a selective ligand for CCR3, Our observations show that the action of RANTES via CCR3 is necessary to regulate Fast expression on HIV-specific CD8(+) T cells that kill through the Fas/FasL, pathway.

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