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1.
Stephen F. Lincoln Andrea M. Hounslow Bruce G. Doddridge John M. Coates 《Inorganica chimica acta》1985,100(2):207-210
Proton NMR studies of N,N-diethylformamide (def) exchange on [M(Me6tren)def]2+ where M = Co and Cu yield: kex (298.2K) = 26.3 ± 2.2, 980 ± 70 s−1; ΔH≠ = 58.3 ± 1.7, 36.3 ± 0.9 kJ mol−1; ΔS≠= −22.2 ± 4.6, −65.9 ± 2.5 J K−1 mol−1; and ΔV≠ = −1.3 ± 0.2, 5.3 ± 0.3 cm3 mol−1 respectively. These data which are consistent with a and d activation modes operating when M = Co and Cu respectively are compared with data for related systems. 相似文献
2.
Exchange of fluorinated glucose across the red-cell membrane measured by 19F-n.m.r. magnetization transfer. 总被引:1,自引:0,他引:1
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The 19F n.m.r. spectrum of 3-fluoro-3-deoxy-D-glucose (3FG) in a red-cell suspension was observed to contain separate resonances from the intra- and extra-cellular populations of both the alpha- and beta-anomers. This phenomenon was used with an n.m.r. spin-transfer procedure to measure the rate of exchange of the anomers across the human red-cell membrane under equilibrium-exchange conditions at 37 degrees C. The beta-anomer crossed the membrane significantly more quickly than the alpha-anomer. At a total 3FG concentration of 9.3 mM; the first-order rate constants for the efflux of the alpha- and beta-anomers were 0.41 +/- 0.15 and 0.88 +/- 0.20 s-1 respectively. The measurable 3FG exchange was inhibited by 75 and 100% respectively by the glucose-transport inhibitors cytochalasin B and phloretin. Glucose inhibited the exchange of 3FG, and the results were consistent with glucose and 3FG binding to the hexose-transport protein with similar affinity. 相似文献
3.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
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AB Zarafi AM Emechebe AD Akpa O Alabi 《Archives Of Phytopathology And Plant Protection》2013,46(4):261-268
Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight. 相似文献
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Marchal LM van de Laar AM Goetheer E Schimmelpennink EB Bergsma J Beeftink HH Tramper J 《Biotechnology and bioengineering》1999,63(3):344-355
The hydrolysis of starch to low-molecular-weight products (normally characterised by their dextrose equivalent (DE), which is directly related to the number-average molecular mass) was studied at different temperatures. Amylopectin potato starch, lacking amylose, was selected because of its low tendency towards retrogradation at lower temperatures. Bacillus licheniformis alpha-amylase was added to 10% [w/w] gelatinised starch solutions. The hydrolysis experiments were done at 50, 70, and 90 degrees C. Samples were taken at defined DE values and these were analysed with respect to their saccharide composition. At the same DE the oligosaccharide composition depended on the hydrolysis temperature. This implies that at the same net number of bonds hydrolysed by the enzyme, the saccharide composition was different. The hydrolysis temperature also influenced the initial overall molecular-weight distribution. Higher temperatures led to a more homogenous molecular weight distribution. Similar effects were observed for alpha-amylases from other microbial sources such as Bacillus amyloliquefaciens and Bacillus stearothermophilus. Varying the pH (5.1, 6.2, and 7.6) at 70 degrees C did not significantly influence the saccharide composition obtained during B. licheniformis alpha-amylase hydrolysis. The underlying mechanisms for B. licheniformis alpha-amylase were studied using pure linear oligosaccharides, ranging from maltotriose to maltoheptaose as substrates. Activation energies for the hydrolysis of individual oligosaccharides were calculated from Arrhenius plots at 60, 70, 80, and 90 degrees C. Oligosaccharides with a degree of polymerisation exceeding that of the substrate could be detected. The contribution of these oligosaccharides increased as the degree of polymerisation of the substrate decreased and the temperature of hydrolysis increased. The product specificity decreased with increasing temperature of hydrolysis, which led to a more equal distribution between the possible products formed. Calculations with the subsite map as determined for the closely related alpha-amylase from B. amyloliquefaciens reconfirmed this finding of a decreased substrate specificity with increased temperature of hydrolysis. Copyright 1999 John Wiley & Sons, Inc. 相似文献
10.
Here we present POCUS (prioritization of candidate genes using statistics), a novel computational approach to prioritize candidate disease genes that is based on over-representation of functional annotation between loci for the same disease. We show that POCUS can provide high (up to 81-fold) enrichment of real disease genes in the candidate-gene shortlists it produces compared with the original large sets of positional candidates. In contrast to existing methods, POCUS can also suggest counterintuitive candidates. 相似文献