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1.
7-Deoxy-7-iodohept-1-enitols react intramolecularly to give 5-carba analogues of pyranoses (pseudo sugars) by the action of tributyltin hydride, which generates a radical at C-7. The configuration at the new chiral centre depends on the relative orientation of the oxygen functions in the starting material and the pattern of substitution. 相似文献
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不同耕作措施对冬小麦-夏玉米复种连作系统土壤有机碳和水分利用效率的影响 总被引:1,自引:1,他引:1
在连续8年田间定位试验的基础上,分析了关中平原冬小麦 夏玉米复种连作系统2008—2009年连续两个生长季期间不同耕作措施(结合秸秆还田和不还田)对土壤有机碳和水分利用率的影响.结果表明: 相对于传统耕作,保护性耕作有利于土壤有机碳、水分利用效率和作物产量的提高,其中在“深松+秸秆还田”耕作模式下的增幅最高,土壤有机碳含量在0~30 cm土层增幅达到19.5%,水分利用效率和作物产量提高了16.9%和20.5%,而免耕模式则有效提高了0~10 cm土层有机碳含量.在该地区土壤和气候条件下,深松结合秸秆粉碎还田是最理想的耕作模式,最有利于土壤有机碳累积,并提高水分利用效率和作物产量. 相似文献
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Wyatt PG Allen MJ Borthwick AD Davies DE Exall AM Hatley RJ Irving WR Livermore DG Miller ND Nerozzi F Sollis SL Szardenings AK 《Bioorganic & medicinal chemistry letters》2005,15(10):2579-2582
This paper covers efforts to discover orally active potent and selective oxytocin antagonists. Screening pooled libraries identified a novel series of 2,5-diketopiperazine derivatives with antagonist activity at the human oxytocin receptor. We report the initial structure-activity relationship investigations and the determination of the stereochemistry of the most potent compounds. 相似文献
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Shi Yu Tillmann Falck Anneleen Daemen Leon-Charles Tranchevent Johan AK Suykens Bart De Moor Yves Moreau 《BMC bioinformatics》2010,11(1):309
Background
This paper introduces the notion of optimizing different norms in the dual problem of support vector machines with multiple kernels. The selection of norms yields different extensions of multiple kernel learning (MKL) such as L ∞, L 1, and L 2 MKL. In particular, L 2 MKL is a novel method that leads to non-sparse optimal kernel coefficients, which is different from the sparse kernel coefficients optimized by the existing L ∞ MKL method. In real biomedical applications, L 2 MKL may have more advantages over sparse integration method for thoroughly combining complementary information in heterogeneous data sources. 相似文献8.
The Indian black berry (Syzygium cumini Skeels) has a great nutraceutical and medicinal properties. As in other fruit crops, the
fruit characteristics are important attributes for differentiation were also determined for different accessions of S. cumini. The fruit
weight, length, breadth, length: breadth ratio, pulp weight, pulp content, seed weight and pulp: seed ratio significantly varied in
different accessions. Molecular characterization was carried out using PCR based RAPD technique. Out of 80 RAPD primers, only
18 primers produced stable polymorphisms that were used to examine the phylogenetic relationship. A sum of 207 loci were
generated out of which 201 loci found polymorphic. The average genetic dissimilarity was 97 per cent among jamun accessions.
The phylogenetic relationship was also determined by principal coordinates analysis (PCoA) that explained 46.95 per cent
cumulative variance. The two-dimensional PCoA analysis showed grouping of the different accessions that were plotted into four
sub-plots, representing clustering of accessions. The UPGMA (r = 0.967) and NJ (r = 0.987) dendrogram constructed based on the
dissimilarity matrix revealed a good degree of fit with the cophenetic correlation value. The dendrogram grouped the accessions
into three main clusters according to their eco-geographical regions which given useful insight into their phylogenetic
relationships. 相似文献
9.
K Michałek M Laszczyńska AK Ciechanowicz A Herosimczyk I Rotter M Oganowska 《Biotechnic & histochemistry》2014,89(5):342-347
Aquaporin 2 (AQP2) is a small, integral tetrameric plasma membrane protein that is expressed in mammalian kidneys. The specific constitution of this protein and its selective permeability to water means that AQP2 plays an important role in hypertonic urine production. Immunolocalization of AQP2 has been studied in humans, monkeys, sheep, dogs, rabbits, rats, mice and adult cattle. We analyzed the expression of AQP2 in kidneys of 7-month-old Polish-Friesian var. black and white male calves. AQP2 was localized in the principal cells of collecting ducts in medullary rays penetrating the renal cortex and in the collecting ducts of renal medulla. AQP2 was expressed most strongly in the apical plasma membrane, but expression was observed also in the intracellular vesicles and basolateral plasma membrane. Our study provides new information concerning the immunolocalization of AQP2 in calf kidneys. 相似文献
10.
Robert Ietswaart Florian Szardenings Kenn Gerdes Martin Howard 《PLoS computational biology》2014,10(12)
Low copy number plasmids in bacteria require segregation for stable inheritance through cell division. This is often achieved by a parABC locus, comprising an ATPase ParA, DNA-binding protein ParB and a parC region, encoding ParB-binding sites. These minimal components space plasmids equally over the nucleoid, yet the underlying mechanism is not understood. Here we investigate a model where ParA-ATP can dynamically associate to the nucleoid and is hydrolyzed by plasmid-associated ParB, thereby creating nucleoid-bound, self-organizing ParA concentration gradients. We show mathematically that differences between competing ParA concentrations on either side of a plasmid can specify regular plasmid positioning. Such positioning can be achieved regardless of the exact mechanism of plasmid movement, including plasmid diffusion with ParA-mediated immobilization or directed plasmid motion induced by ParB/parC-stimulated ParA structure disassembly. However, we find experimentally that parABC from Escherichia coli plasmid pB171 increases plasmid mobility, inconsistent with diffusion/immobilization. Instead our observations favor directed plasmid motion. Our model predicts less oscillatory ParA dynamics than previously believed, a prediction we verify experimentally. We also show that ParA localization and plasmid positioning depend on the underlying nucleoid morphology, indicating that the chromosomal architecture constrains ParA structure formation. Our directed motion model unifies previously contradictory models for plasmid segregation and provides a robust mechanistic basis for self-organized plasmid spacing that may be widely applicable. 相似文献