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排序方式: 共有72条查询结果,搜索用时 31 毫秒
31.
NG-Monoethyl-l-arginine, a putative in vivo product after administration of the potent hepatocarcinogen l-ethionine to rats, has been chemically synthesized by coupling N-ethyl, S-methylthiopseudouronium iodide with α-amino-blocked l-ornithine. The structure of the compound as NG-monoethyl-l-arginine was confirmed by 13C NMR. Its elution time on an automatic amino acid analyzer, Rf values using thin-layer chromatography, and isoelectric point have been compared with those of NG-monomethyl-l-arginine. 相似文献
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Molecular Genetics and Genomics - Glucose represses mitochondrial biogenesis and the fermentation of maltose, galactose and sucrose in yeast. We have analyzed the effect of D-glucosamine on these... 相似文献
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The purpose of this study was to investigate the need for and choice of stratification factors, and the effects of blinding
and placebo in a clinical experiment. Eighty dogs with canine hip dysplasia (CHD) were included in a randomized, placebo-controlled
and double blind clinical trial with stratified parallel group design, in which body weight and degree of CHD were used as
stratification factors. Thirty-eight dogs were allocated to gold bead implantation and 42 to placebo. After six months, 33
of the 42 placebo-treated dogs received gold bead implantation in an open study lasting a further 18 months. The main outcome
variable in the study was change in pain signs of CHD as assessed by the owner. No significant difference in the main outcome
variable, regardless of the treatment given, could be detected in the two chosen stratification factors. The only factor to
influence the main outcome variable significantly was age. The blinding procedure used in the study, in which 60% of the owners
correctly guessed the treatment given, was found sufficient. Of those who guessed the treatment erroneously, 88% believed
the treatment given was gold bead implantation. The treatment efficacy after six months in the blinded treatment group was
found to be significantly larger compared to the efficacy obtained in the open study. A significant placebo effect was therefore
detected. Conclusion and Clinical Relevance: The age of the dogs influenced the outcome of the CHD treatment, and is recommended
as a stratification factor. A significant placebo effect has to be expected and an optimal blinding procedure is necessary
in similar clinical studies. 相似文献
37.
N-ethyl maleimide sensitive factor (NSF) belongs to the AAA family of ATPases and is involved in a number of cellular functions, including vesicle fusion and trafficking of membrane proteins. We present the three-dimensional structure of the hydrolysis mutant E329Q of NSF complexed with an ATP-ADP mixture at 11 A resolution by electron cryomicroscopy and single-particle averaging of NSF.alpha-SNAP.SNARE complexes. The NSF domains D1 and D2 form hexameric rings that are arranged in a double-layered barrel. Our structure is more consistent with an antiparallel orientation of the two rings rather than a parallel one. The crystal structure of the D2 domain of NSF was docked into the EM density map and shows good agreement, including details at the secondary structural level. Six protrusions corresponding to the N domain of NSF (NSF-N) emerge from the sides of the D1 domain ring. The density corresponding to alpha-SNAP and SNAREs is located on the 6-fold axis of the structure, near the NSF-N domains. The density of the N domain is weak, suggesting conformational variability in this part of NSF. 相似文献
38.
Smith AB Favor DA Sprengeler PA Guzman MC Carroll PJ Furst GT Hirschmann R 《Bioorganic & medicinal chemistry》1999,7(1):9-22
The molecular modeling, synthesis, and elucidations of the solid state and solution structures of N-methylated 3,5-linked bispyrrolin-4-ones are described. Prior investigations established that the 3,5-linked pyrrolin-4-one based scaffold can be incorporated into mimics of beta-sheet/beta-strands and into potent, orally bioavailable inhibitors of the HIV-1 protease. To extend the utility of this scaffold beyond that of the initially designed mimics of beta-sheet/beta-strands, we have now explored the structure of N-methylated pyrrolinones. Molecular modeling indicated that N-methylated bispyrrolinones could adopt three low-energy backbone conformations (ca. 165 degrees, 289 degrees, and 320 degrees). Upon their successful synthesis, structural elucidation both in the solid state and in solution revealed the existence of two of the three predicted backbone conformers (ca. 165 degrees and 289 degrees). Two structures were particularly noteworthy and completely unexpected. Mono-N-methyl bispyrrolinone (+)-1 self assembled in the solid state to form a novel helix, while the acetylene-linked dimer of (+)-1, designed to potentiate the observed helical array, instead associated via an intermolecular hydrogen bond in parallel columns. These serendipitous observations led us to speculate that the pyrrolinone moiety may in fact represent a privileged nonpeptide scaffold, able to mimic not only the extended beta-sheet/beta-strand conformation as initially targeted, but also diverse conformations including those analogous to beta-turns and helices. These seemingly unlimited conformations greatly expand the scope of this scaffold for the development of low-molecular weight ligands for biologically important macromolecules. 相似文献
39.
Naomi Eidelman Alan Boyde Andrew J Bushby Peter GT Howell Jirun Sun Dale E Newbury Frederick W Miller Pamela G Robey Lisa G Rider 《Arthritis research & therapy》2009,11(5):R159-21
Introduction
Calcified deposits (CDs) in skin and muscles are common in juvenile dermatomyositis (DM), and less frequent in adult DM. Limited information exists about the microstructure and composition of these deposits, and no information is available on their elemental composition and contents, mineral density (MD) and stiffness. We determined the microstructure, chemical composition, MD and stiffness of CDs obtained from DM patients. 相似文献40.
We calculate the displacement of a single spherical particle from the minimum of a harmonic well positioned near a plane wall and immersed in a uniform flow. A failure to account for the fluctuations in particle position orthogonal to the plane (leading to fluctuations in hydrodynamic drag) results in large discrepancies, with the naive displacement calculated by assuming no fluctuations in the balance of forces. The chief criterion for neglecting such fluctuations is that the stiffness of the harmonic potential exceeds the thermal stresses on the particle by at least two orders of magnitude. For micrometer-diameter particles typically employed in force spectroscopy of DNA, macromolecules, and molecular motors, this can lead to errors of up to 100% in the measured properties. The Supporting Material to the article provides an implementation of this model intended to fit experimental measurements for the stiffness of the harmonic potential constraining the particle. 相似文献