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排序方式: 共有541条查询结果,搜索用时 390 毫秒
521.
Solanky KS Bailey NJ Holmes E Lindon JC Davis AL Mulder TP Van Duynhoven JP Nicholson JK 《Journal of agricultural and food chemistry》2003,51(14):4139-4145
Flavonoid consumption via tea drinking has been attributed a number of potential health benefits including cancer prevention, anti-inflammatory action, and cardioprotectant activity. Although the predominant flavonoids in fresh leaf and green tea are known to be flavan-3-ols and flavan-3-O-gallates ("the catechins"), the biochemical effects of tea polyphenol consumption on living systems are generally poorly understood. Metabonomic methods utilizing (1)H NMR spectroscopy of biofluids and principal component analysis (PCA) have been applied to investigate the bioavailability and metabolic responses of rats to a single dose of 22 mg of epicatechin (EC) dissolved in water. Urine samples were collected twice daily (0-8 and 8-24 h) from male Sprague-Dawley rats (n = 10) prior to dosing and for 2 days after dosing. A series of subtle urinary biochemical effects were evident from the (1)H NMR spectra showing that EC was both bioavailable and biochemically active. The identifiable biochemical effects associated with EC dosing included decreased urinary concentrations of taurine, citrate, dimethylamine, and 2-oxoglutarate. These effects were predominately seen within the first 8 h after dosing. EC metabolites were also observed in the urine during this time period. PCA of later time points after dosing (24-32 and 32-48 h) showed that the effects of EC were reversible. This is the first in vivo study demonstrating the overall endogenous metabolic effects of EC consumption and shows the bioavailability of EC via metabolic effects and excretion of EC metabolites. 相似文献
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Evidence has been found that the earth is immersed in a large volume of glowing helium ions. This ionic glow, at 304 angstroms, is similar to the geocoronal hydrogen glow in that it extends to very high altitudes, but it is unique in that it is largely confined to the closed field line portion of the magnetosphere. Because of its magnetic containment, this ionic radiation is called the "magnetoglow." Observations of the magnetoglow from inside and outside the magnetospheric cavity promise to provide a valuable means of studying the structural dynamics of the magnetosphere. 相似文献
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Alpha 2-antiplasmin Enschede: alanine insertion and abolition of plasmin inhibitory activity 总被引:8,自引:0,他引:8
W E Holmes H R Lijnen L Nelles C Kluft H K Nieuwenhuis D C Rijken D Collen 《Science (New York, N.Y.)》1987,238(4824):209-211
An abnormal alpha 2-antiplasmin that is associated with a serious bleeding tendency has been found in a Dutch family and is referred to as alpha 2-antiplasmin Enschede. This abnormal alpha 2-antiplasmin is converted from an inhibitor of plasmin to a substrate. The molecular defect of alpha 2-antiplasmin Enschede, as revealed by sequencing of cloned genomic DNA fragments, consists of an alanine insertion near the active site region of the molecule. Substitution of this fragment into complementary DNA for a wild-type alpha 2-antiplasmin yields a translation product with physical and functional properties typical of the abnormal alpha 2-antiplasmin Enschede. The naturally occurring mutant may serve as a model for investigating the structures that determine the properties of an inhibitor versus those of a substrate in serine protease inhibitors. 相似文献
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Holmes SJ 《Science (New York, N.Y.)》1925,61(1569):77-79
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Holmes SJ 《Science (New York, N.Y.)》1914,40(1025):271-272
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Sanvitto D Pulizzi F Shields AJ Christianen PC Holmes SN Simmons MY Ritchie DA Maan JC Pepper M 《Science (New York, N.Y.)》2001,294(5543):837-839
We report transport of electron-hole complexes in semiconductor quantum wells under applied electric fields. Negatively charged excitons (X-), created by laser excitation of a high electron mobility transistor, are observed to drift upon applying a voltage between the source and drain. In contrast, neutral excitons do not drift under similar conditions. The X- mobility is found to be as high as 6.5 x 10(4) cm2 V-1 s-1. The results demonstrate that X- exists as a free particle in the best-quality samples and suggest that light emission from opto-electronic devices can be manipulated through exciton drift under applied electric fields. 相似文献