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51.
Magnet S Arbeloa A Mainardi JL Hugonnet JE Fourgeaud M Dubost L Marie A Delfosse V Mayer C Rice LB Arthur M 《The Journal of biological chemistry》2007,282(18):13151-13159
We report here the first direct assessment of the specificity of a class of peptidoglycan cross-linking enzymes, the L,D-transpeptidases, for the highly diverse structure of peptidoglycan precursors of Gram-positive bacteria. The lone functionally characterized member of this new family of active site cysteine peptidases, Ldt(fm) from Enterococcus faecium, was previously shown to bypass the D,D-transpeptidase activity of the classical penicillin-binding proteins leading to high level cross-resistance to glycopeptide and beta-lactam antibiotics. Ldt(fm) homologues from Bacillus subtilis (Ldt(Bs)) and E. faecalis (Ldt(fs)) were found here to cross-link their cognate disaccharide-peptide subunits containing meso-diaminopimelic acid (mesoDAP(3)) and L-Lys(3)-L-Ala-L-Ala at the third position of the stem peptide, respectively, instead of L-Lys(3)-d-iAsn in E. faecium. Ldt(fs) differed from Ldt(fm) and Ldt(Bs) by its capacity to hydrolyze the L-Lys(3)-D-Ala(4) bond of tetrapeptide (L,D-carboxypeptidase activity) and pentapeptide (L,D-endopeptidase activity) stems, in addition to the common cross-linking activity. The three enzymes were specific for their cognate acyl acceptors in the cross-linking reaction. In contrast to Ldt(fs), which was also specific for its cognate acyl donor, Ldt(fm) tolerated substitution of L-Lys(3)-D-iAsn by L-Lys(3)-L-Ala-L-Ala. Likewise, Ldt(Bs) tolerated substitution of mesoDAP(3) by L-Lys(3)-D-iAsn and L-Lys(3)-L-Ala-L-Ala in the acyl donor. Thus, diversification of the structure of peptidoglycan precursors associated with speciation has led to a parallel evolution of the substrate specificity of the L,D-transpeptidases affecting mainly the recognition of the acyl acceptor. Blocking the assembly of the side chain could therefore be used to combat antibiotic resistance involving L,D-transpeptidases. 相似文献
52.
Determination of urea, allantoin and lysine pyroglutamate in cosmetic samples by hydrophilic interaction chromatography 总被引:1,自引:0,他引:1
Ph. Dallet L. Labat E. Kummer J. P. Dubost 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,742(2)
A new HPLC method using a Polyhydroxyethyl A column involving hydrophilic interaction chromatography (HILIC) is described for the simultaneous determination of urea, allantoin and lysine pyroglutamate in a cosmetic cream. Validation of the method was accomplished with respect to linearity, repeatability and limits of detection/quantification. Compound recoveries approach 100% with acceptable RSD values. The method is very simple since no derivatisation is necessary. Furthermore, it allows the rapid and direct chromatographic analysis of urea and hence could provide an alternative to other methods used to determine this compound in biological or cosmetic samples. 相似文献
53.
54.
Lolona Rakotobe Lengo Mambu Alexandre Deville Lionel Dubost Victor Jeannoda Danielle Rakoto Bernard Bodo 《Phytochemistry》2010,71(8-9):1007-1013
Two clerodane diterpenoids, antadiosbulbins A and B and two 19-norclerodane diterpenes, 8-epidiosbulbins E and G along with the known diosbulbin E as well as nine known phenolics including five phenanthrenes and stilbenes and four flavonoids were isolated from the ethyl acetate soluble part of the methanolic extract of the tubers of Dioscorea antaly, a yam endemic to Madagascar. Structures were determined by analysis of the spectral data, mainly 2D-NMR and mass spectrometry. 相似文献
55.
Summary The diets of three major groups of frugivores-folivores of an African rain forest (squirrels, ruminants, primates) are compared and the relationship of food habits to body weight, habitat and foraging height examined. A number of common trends in the trophic patterns are found in the three groups. Over half of the fruit species identified in the diets of any one taxon are exploited in common with one or more of the others. The parts of fruit usually eaten are different for each group but for a number of species, the same fruit parts are searched for by the species of the three taxa. 相似文献
56.
When rat liver 60S ribosomal subunits were heated in phosphate buffer in the presence of MgCl2, 5S RNA was released in the form of a nucleoprotein complex (RNPH), which was isolated either by electrophoresis in polyacrylamide gel or centrifugation through a sucrose gradient. In addition to L5 several proteins of functional significance were identified in the complex: the acidic phosphoproteins P1-P2 and, as weaker spots, L3-L4, L6-L7 and L22. Most of these proteins were also found, but only as traces, in the RNPEDTA used as a control. RNPH was able to associate with 40S subunits. Our results support the interpretation that RNPH is located at the subunits' interface, at or near the peptidyl-transferase center. 相似文献
57.
Sébastien Triboulet Vincent Dubée Lauriane Lecoq Catherine Bougault Jean-Luc Mainardi Louis B. Rice Mélanie Ethève-Quelquejeu Laurent Gutmann Arul Marie Lionel Dubost Jean-Emmanuel Hugonnet Jean-Pierre Simorre Michel Arthur 《PloS one》2013,8(7)
Active-site serine D,D-transpeptidases belonging to the penicillin-binding protein family (PBPs) have been considered for a long time as essential for peptidoglycan cross-linking in all bacteria. However, bypass of the PBPs by an L,D-transpeptidase (Ldtfm) conveys high-level resistance to β-lactams of the penam class in Enterococcus faecium with a minimal inhibitory concentration (MIC) of ampicillin >2,000 µg/ml. Unexpectedly, Ldtfm does not confer resistance to β-lactams of the carbapenem class (imipenem MIC = 0.5 µg/ml) whereas cephems display residual activity (ceftriaxone MIC = 128 µg/ml). Mass spectrometry, fluorescence kinetics, and NMR chemical shift perturbation experiments were performed to explore the basis for this specificity and identify β-lactam features that are critical for efficient L,D-transpeptidase inactivation. We show that imipenem, ceftriaxone, and ampicillin acylate Ldtfm by formation of a thioester bond between the active-site cysteine and the β-lactam-ring carbonyl. However, slow acylation and slow acylenzyme hydrolysis resulted in partial Ldtfm inactivation by ampicillin and ceftriaxone. For ampicillin, Ldtfm acylation was followed by rupture of the C5–C6 bond of the β-lactam ring and formation of a secondary acylenzyme prone to hydrolysis. The saturable step of the catalytic cycle was the reversible formation of a tetrahedral intermediate (oxyanion) without significant accumulation of a non-covalent complex. In agreement, a derivative of Ldtfm blocked in acylation bound ertapenem (a carbapenem), ceftriaxone, and ampicillin with similar low affinities. Thus, oxyanion and acylenzyme stabilization are both critical for rapid L,D-transpeptidase inactivation and antibacterial activity. These results pave the way for optimization of the β-lactam scaffold for L,D-transpeptidase-inactivation. 相似文献
58.
Tschamber T Gessier F Dubost E Newsome J Tarnus C Kohler J Neuburger M Streith J 《Bioorganic & medicinal chemistry》2003,11(17):3559-3568
The syntheses of four glyco-imidazoles, which are pentose-derivatives belonging to the D-series, as well as the syntheses of their L-enantiomers, are reported. Starting from the known linear xylo, lyxo, arabino, and ribo imidazolo-pentoses in both the L- and the D-series, intramolecular Walden inversion led to the corresponding arabino, ribo, xylo, and lyxo pyrrolidinopentoses in the D- and the L-series, respectively, protection and deprotection steps being unavoidable prerequisites. The structures and configurations of all eight pyrrolidinopentoses were determined unambiguously, by a combination of 1H/13C NMR spectroscopy, circular dichroism and [alpha](D) values, in conjunction with single-crystal X-ray diffraction analysis of the L-xylo stereoisomer. Examination of the inhibitory properties of these imidazolo-pyrrolidinoses against six commonly encountered glycosidases led to the conclusion that by and large the L-stereoisomers are inactive, whereas three out the four D-stereoisomers proved to be poor to moderate inhibitors. It appears therefore that the most basic N(1) atom is not located in an optimal topology to be protonated easily inside the enzyme's active site. 相似文献
59.
Lise Alonso Thomas Pommier Bernard Kaufmann Audrey Dubost David Chapulliot Jeanne Dor Christophe J. Douady Yvan Moënne‐Loccoz 《Molecular ecology》2019,28(14):3383-3394
Limestone areas across the world develop karstic caves, which are populated by a wide range of macro‐ and microorganisms. Many of these caves display Paleolithic art or outstanding speleothems, and in the last century they have been subjected to anthropization due to touristic management and intense human frequentation. Despite their cultural importance and associated conservation issues, the impact of anthropization on cave biodiversity is not known. Here, we show that anthropization is associated with specific cave biota modifications. We compared diversity in four pristine caves, four anthropized show caves, and the iconic Lascaux Cave with even stronger anthropization. The predominant microbial higher taxa were the same in all caves, but the most anthropized cave (Lascaux) was unique as it differed from the eight others by a higher proportion of Bacteroidetes bacteria and the absence of Euryarchaeota and Woesearchaeota archaea. Anthropization resulted in lower diversity and altered community structure for bacteria and archaea on cave walls, especially in Lascaux, but with a more limited effect on microeukaryotes and arthropods. Our findings fill a key gap in our understanding of the response of karstic communities to anthropization, by revealing that tourism‐related anthropization impacts on the prokaryotic microbiome rather than on eukaryotic residents, and that it shapes cave biota irrespective of cave natural features. 相似文献
60.
A.M. Reboud S. Dubost M. Buisson J.P. Reboud 《Biochemical and biophysical research communications》1980,93(3):974-978
When 40S subunits are irradiated at 254nm in presence of [3H] poly (U), formation of a 40S subunit-poly (U) complex can be demonstrated either by filtration technique at low Mg++ concentration or by polyacrylamide gel electrophoresis. No stable complex was detected using unirradiated samples under the same conditions. Electrophoresis of this complex in the presence of dodecyl sulfate showed that part of the poly (U) directly associates with 18S RNA. This association is not through proteins, since it is not disrupted by pronase treatment. 相似文献