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1.
KL Britton HF Rogers Y Asano T Dairi Y Kato TJ Stillman DW Rice 《Acta crystallographica. Section D, Biological crystallography》1998,53(4):124-126
The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres. 相似文献
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Yi-Ming Pai William P. Weber Kenneth L. Servis 《Journal of organometallic chemistry》1985,288(3):269-273
29Si NMR spectra of polymethylhydrosiloxanes, Me3SiO[MeHSiO]nSiMe3 from n = 3 to 8 and 35, have been determined. Both chemical shifts and spin-lattice relaxation times (T1) have been measured. The stereochemistry at the adjacent chiral MeHSiO unit influences the nearest neighbor 29Si chemical shift. The effect of chain length and position of MeHSiO units on T1 values for Me3SiO[MeHSiO]nSiMe3 systems are discussed. 相似文献
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LUDVÍK BENEŠ KLÁRA MELÁNOVÁ JAN SVOBODA VÍTĚZSLAV ZIMA 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):289-293
Intercalates of o-, m-, and p-toluidine into α-Zr(HPO4)2 · H2O were prepared and characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. As follows from IR, toludine molecules are protonated in the interlayer space. Toluidine molecules are arranged in a bimolecular way in the intercalates containing more than 1.5 toluidine molecules per Zr atom. On the other hand, a monolayer of the toluidine molecules is supposed in the intercalates with less than one toluidine molecule per Zr atom. 相似文献
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The free energy as a function of the reaction coordinate (rc) is the key quantity for the computation of equilibrium and kinetic quantities. When it is considered as the potential of mean force, the problem is the calculation of the mean force for given values of the rc. We reinvestigate the PMCF (potential of mean constraint force) method which applies a constraint to the rc to compute the mean force as the mean negative constraint force and a metric tensor correction. The latter allows for the constraint imposed to the rc and possible artefacts due to multiple constraints of other variables which for practical reasons are often used in numerical simulations. Two main results are obtained that are of theoretical and practical interest. First, the correction term is given a very concise and simple shape which facilitates its interpretation and evaluation. Secondly, a theorem describes various rcs and possible combinations with constraints that can be used without introducing any correction to the constraint force. The results facilitate the computation of free energy by molecular dynamics simulations. 相似文献
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Dae-Ki Kang Kenneth L. Servis Anton B. Burg 《Magnetic resonance in chemistry : MRC》1971,3(1):101-112
Both the diphosphine CH3CF3PPCH3CF3 and the thio-bisphosphine CH3CF3PSPCH3CF3 show 19F and 31P NMR spectra indicative of diastereomeric mixtures of d,l and meso isomers. The temperature-dependent reversible interconversions of the isomers have been attributed to the inversion at the phosphorus atom. The equilibrium constants for the isomerization reactions have been measured at various temperatures. The fluorine NMR spectra of the meso and d,l isomers of CD3CF3PSPCD3CF3 have been analyzed as M3XX′M3′ spin systems. Good agreement is found between the observed and calculated spectra. The five-bond fluorine-fluorine coupling constant of the low-field isomer is larger than that of the high-field isomer. The 19F NMR spectra of (CF3)2PP(CF3)2, (CF3)2POP(CF3)2, (CF3)2PSP(CF3)2, CH3CF3PPCH3CF3 and CH3CF3PSPCH3CF3 have been examined over a wide range of temperatures in an attempt to correlate the data to the geometries of these compounds. 相似文献
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The carbon-13 chemical shifts and coupling constants (J[13C? 199Hg]) have been determined for a series of eleven symmetrically substituted organomercurials. Empirical substituent parameters can be calculated which correlate observed and predicted chemical shifts for dialkylmercurials. 相似文献
9.
Kenneth L. Servis Joseph Casanova Manfred Geisel 《Magnetic resonance in chemistry : MRC》1969,1(3):209-212
The two stereochemically distinct two-bond carbon-13- hydrogen coupling constants J(13C? CH), for α-chlorostyrene-α-13C have been shown to be of similar magnitude but opposite sign (?6.3 and +5.6 Hz). A simple additivity relationship which adequately reproduces all the reported J(13C? CH) values for chloroethylenes has been found. 相似文献
10.
Fran?oise Vuadens David Crettaz Corinne Scelatta Catherine Servis Manfredo Quadroni Willy-Vincent Bienvenut Philippe Schneider Patrick Hohlfeld Lee A Applegate Jean-Daniel Tissot 《Electrophoresis》2003,24(7-8):1281-1291
In order to gain insight into the biology of fetal skin during culture, cellular proteins were studied during four culture passages (P00, P01, P04 as well as P10) using high-resolution two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS). Bioinformatic analyses were focused on a region of each gel corresponding to pI between 4 and 8 and M(r) from 8000 to 35 000. In this area, 373 +/- 42 spots were detected (N = 18). Twenty-six spots presented an integrated intensity that increased in the higher passages, whereas five spots showed a progressively lower intensity in subsequent passaging. MS analysis was performed on spots that were unambiguously identified on preparative 2-D gels. Among the 26 spots showing an increased size between P00 and P10, 9 were identified, and corresponded to 3 proteins: (i) peptidyl-prolyl cis-trans isomerase A (P05092; cyclophilin A or cyclosporin A-binding protein), (ii) triosephosphate isomerase (P00938), and (iii) enoyl-CoA hydratase (P30084). Among these nine identified spots, three were absent at P00, but were present at P10. They corresponded to isoforms of peptidyl-prolyl cis-trans isomerase and triosephosphate isomerase, respectively. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses of the acidic isoforms of triosephosphate isomerase showed modifications of cysteine residues to cysteic acid. All these isoforms were clearly present in the skin cells of a 4-year-old child, as well as in skin cells from a 80-year-old man, at P00. These observations probably reflect either an oxidative stress related to cell culture, or, alternatively, maturation, differentiation and the aging of the cells. 相似文献