SPAM : a multiprocessor execution driven simulation Kernel

Trace driven simulation is a well known technique for performance evaluation of single processor computers. However, trace driven simulation introduces distortions when used to simulate multiprocessor architectures. Execution driven simulation is the only technique that gives accurate simulation results for multiprocessor architectures though it is difficult to implement. Thisd paper presents SPAM, a simulation kernel that simplifies the construction of execution driven simulators for shared memory multiprocessors. The kernel provides a tracing tool and a set of primitives which allow the execution, tracing and simulation of shared memory parallel applications on a single processor computer. The performance of the kernel allows the simulation of real sized parallel applications in a reasonnable time

Structure of Tagatose-1,6-bisphosphate Aldolase. Insight into chiral discrimination, mechanism, and specificity of class II aldolases

Tagatose-1,6-bisphosphate aldolase (TBPA) is a tetrameric class II aldolase that catalyzes the reversible condensation of dihydroxyacetone phosphate with glyceraldehyde 3-phosphate to produce tagatose 1,6-bisphosphate. The high resolution (1.45 Å) crystal structure of the Escherichia coli enzyme, encoded by the agaY gene, complexed with phosphoglycolohydroxamate (PGH) has been determined. Two subunits comprise the asymmetric unit, and a crystallographic 2-fold axis generates the functional tetramer. A complex network of hydrogen bonds position side chains in the active site that is occupied by two cations. An unusual Na(+) binding site is created using a interaction with Tyr(183) in addition to five oxygen ligands. The catalytic Zn(2+) is five-coordinate using three histidine nitrogens and two PGH oxygens. Comparisons of TBPA with the related fructose-1,6-bisphosphate aldolase (FBPA) identifies common features with implications for the mechanism. Because the major product of the condensation catalyzed by the enzymes differs in the chirality at a single position, models of FBPA and TBPA with their cognate bisphosphate products provide insight into chiral discrimination by these aldolases. The TBPA active site is more open on one side than FBPA, and this contributes to a less specific enzyme. The availability of more space and a wider range of aldehyde partners used by TBPA together with the highly specific nature of FBPA suggest that TBPA might be a preferred enzyme to modify for use in biotransformation chemistry

Исследование ультрадисперсных оксидов меди, полученных плазмодинамическим методом

The synthesis of copper oxides has a great importance due to the fact these materials are widely used in superconductors manufacturing. It’s known that properties of materials in nanodispersed conditions are improved. In this article, an analysis of ultradispersed plasmodynamic synthesis product obtained using coaxial magnetoplasma accelerator with copper electrodes was carried out. The obtained powder was analyzed by X-ray diffractometer Shimadzu XRD 7000 using the temperature consoles Anton Paar TTK450. Using this analysis such phases as copper Cu, copper oxide (I) Cu2O, copper oxide (II) CuO, and copper hydroxide hydrate Cu(OH)[2]•H[2]O were identified in the product. By gradually heating, the powder to the temperature of 800 °С the phase change was observed. The mass of copper oxide increased up to 96% and copper hydroxide hydrate

Synthesis of the constrained glutamate analogues (2S,1 ' R,2 ' R)- and (2S,1 ' S,2 ' S)-2- (2 'carboxycyclobutyl)glycines L-CBG-II and L-CBG-I by enzymatic transamination

Optically pure trans-cyclobutane analogues of glutamic acid are prepared by highly selective enzymatic transamination of a single racemic trans-cyclobutane α-ketoglutaric acid derivative 5, which is synthesized in five steps from maleic anhydride. (2S,1′R,2′R)- and (2S,1′S,2′S)-2-(2′-carboxycyclobutyl)glycines L-CBG-II and L-CBG-I are obtained using aspartate aminotransferase (AAT) and branched chain aminotransferase (BCAT), respectively

Chemo-enzymatic synthesis of a series of 2,4-syn-functionalized (S)-glutamate analogues: new insight into the structure-activity relation of ionotropic glutamate receptor subtypes 5, 6, and 7.

International audience(S)-Glutamic acid (Glu) is the major excitatory neurotransmitter in the central nervous system (CNS) activating the plethora of ionotropic Glu receptors (iGluRs) and metabotropic Glu receptors (mGluRs). In this paper, we present a chemo-enzymatic strategy for the enantioselective synthesis of five new Glu analogues 2a−f (2d is exempt) holding a functionalized substituent in the 4-position. Nine Glu analogues 2a−j are characterized pharmacologically at native 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), kainic acid (KA), and N-methyl-D-aspartic acid (NMDA) receptors in rat synaptosomes as well as in binding assays at cloned rat iGluR5−7 subtypes. A detailed in silico study address as to why 2h is a high-affinity ligand at iGluR5−7 (Ki = 3.81, 123, 57.3 nM, respectively), while 2e is only a high affinity ligand at iGluR5 (Ki = 42.8 nM). Furthermore, a small series of commercially available iGluR ligands are characterized in iGluR5−7 bindin

Chronic exposure to glufosinate-ammonium induces spatial memory impairments, hippocampal MRI modifications and glutamine synthetase activation in mice

International audienceGlufosinate-ammonium (GLA), the active compound of a worldwide-used herbicide, acts by inhibiting the plant glutamine synthetase (GS) leading to a lethal accumulation of ammonia. GS plays a pivotal role in the mammalian brain where it allows neurotransmitter glutamate recycling within astroglia. Clinical studies report that an acute GLA ingestion induces convulsions and memory impairment in humans. Toxicological studies performed at doses used for herbicidal activity showed that GLA is probably harmless at short or medium range periods. However, effects of low doses of GLA on chronically exposed subjects are not known. In our study, C57BL/6J mice were treated during 10 weeks three times a week with 2.5, 5 and 10 mg/kg of GLA. Effects of this chronic treatment were assessed at behavioral, structural and metabolic levels by using tests of spatial memory, locomotor activity and anxiety, hippocampal magnetic resonance imaging (MRI) texture analysis, and hippocampal GS activity assay, respectively. Chronic GLA treatments have effects neither on anxiety nor on locomotor activity of mice but at 5 and 10 mg/kg induce (1) mild memory impairments, (2) a modification of hippocampal texture and (3) a significant increase in hippocampal GS activity. It is suggested that these modifications may be causally linked one to another. Since glutamate is the main neurotransmitter in hippocampus where it plays a crucial role in spatial memory, hippocampal MRI texture and spatial memory alterations might be the consequences of hippocampal glutamate homeostasis modification revealed by increased GS activity in hippocampus. The present study provides the first data that show cerebral alterations after chronic exposure to GLA