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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
2.
Fine structure is reported in the 69,71Ga NQR spectra of GaS and GaSe. The 69Ga (I = 32) and 71Ga (I = 32) spectra are different for each compound. This is attributed to an indirect spin-spin interaction between nearest-neighbour Ga atom pairs. A model giving reasonable quantitative agreement with experiment is presented. 相似文献
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T.J. Bastow M.E. Hobday M.E. Smith H.J. Whitfield 《Solid state nuclear magnetic resonance》1996,5(4):293-303
The NMR interactions of crystalline phases in the system Na2O-ZrO2-SiO2 have been studied by a combination of static and magic angle spinning NMR methods for the first time. A full multinuclear (17O, 23Na, 29Si and 91Zr) approach has been employed that allows the phases to be clearly identified. NMR interactions such as 29Si isotropic chemical shift correlate with the known structural units present. For 23Na the different sites can often be distinguished on the basis of differing quadrupolar interactions. 相似文献
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Pulsed Fourier transform NQR spectroscopy has been used to study polytypism in the monochalcogenides GaS, GaSe and InSe at 77 K. The spectrum of GaS was consistent with a major contribution from the β phase but showed evidence of higher polytypes, possibly due to ? or γ type faulting. The GaSe spectrum is simply interpreted as an equal mixture of ? and γ types. The four InSe spectra (115In), showed a multiplicity of lines. The sharpness of the NQR lines of all spectra suggests the existence of regions with a hitherto overlooked high degree of order. 相似文献
6.
A characterisation by 14N NMR of the binary nitrides AlN and BN is presented. Both the static and magic angle spinning (MAS) lineshapes have been investigated in order to determine, or set upper limits on, the nuclear quadrupole coupling (Cq) at the nitrogen site. Additional data are given for the Cq values at the Al and B sites. A comparison is made with other similar (mainly wurtzite) binary compounds for which Cq is known at each atomic site. 相似文献
7.
T. J. Bastow 《Chemical physics letters》2003,380(5-6):516-520
67Zn NMR has been used as a probe to measure the electric field gradients at the metal site in the zinc halides ZnF2, γ-ZnCl2, ZnBr2 and ZnI2 and Rb2ZnCl4 at room temperature. In addition two hydration states have been detected for ZnSO4. For ZnF2 and γ-ZnCl2 an ab initio calculation of the electric field gradient at the Zn site using the W
97 code agrees well with the experimentally observed values. 相似文献
8.
Peilan Ding Daofeng Chen KennethF. Bastow AlexanderK. Nyarko Xihong Wang Kuo‐Hsiung Lee 《Helvetica chimica acta》2004,87(10):2574-2580
Three new flavonoids, which are isoprenylated by fused 2,2‐dimethyl‐3,4‐dihydro‐2H‐pyran moieties, were isolated from the roots of Sophora flavescens and named flavenochromanes A–C ( 1 – 3 ). Their structures were elucidated by spectroscopic methods, including 2D‐NMR techniques. Flavenochromane C ( 3 ) showed strong cytotoxic activity against A549 (lung carcinoma), 1A9 (ovarian carcinoma), KB (epidermoid carcinoma of the nasopharynx), and KB‐Vin (drug‐resistant variant KB) cell lines with IC50 values ≤1.7 μM , and significant activity against the MCF‐7 (breast adenocarcinoma) cell line with an IC50 value of 3.6 μM . Flavenochromane B ( 2 ) displayed slightly lower inhibitory effects (IC50 3.2–6.9 μM ) as compared with 3 . 相似文献
9.
(1)H, (27)Al, (29)Si and (39)K solid-state NMR are reported from a Hungarian illite 2:1 clay for samples heated up 1600 degrees C. This single-phase sample has a small amount of aluminium substitution in the silica layer and very low iron-content ( approximately 0.4wt%). Thermal analysis shows several events that can be related to features in the NMR spectra, and hence changes in the atomic scale structure. As dehydroxylation occurs there is increasing AlO(4) and AlO(5)-contents. The silica and gibbsite layers become increasingly separated as the dehydroxylation progresses. Between 900 and 1000 degrees C the silica layer forms a potassium aluminosilicate glass. The gibbsite-layer forms spinel/gamma-Al(2)O(3) and some aluminium-rich mullite. Then on heating to 1600 degrees C changes in the (29)Si and (27)Al MAS NMR spectra are consistent with the aluminosilicate glass increasing its aluminium-content, the amount of mullite increasing probably with its silicon-content also increasing, and some alpha-Al(2)O(3) forming. 相似文献
10.
Iris H Hall E Stacy Hall L K Chi M C Miller Iii Ken F Bastow A Sood B F Spielvogel 《应用有机金属化学》1992,6(2):229-239
Studies on the mode of action of two boroncontaining anti-neoplastic agents, ethylamine-carboxyborane and triphenylphosphine-carboxyborane, are reported. The major site of inhibition was in the pyrimidine de nove synthetic pathway at orotidine monophosphate decarboxylase activity. Additional sites which may facilitate the inhibition of cell growth were IMP dehydrogenase, thymidine kinase, TMP kinase and TDP kinase, m-RNA, r-RNA and t-RNA polymerase activities as well as topoisomerase II activity. The reduction in enzyme activities led to sufficient reduction of d(NTP) levels to suppress DNA synthesis and cell growth. DNA strand scission was evident in the presence of drug. Multiple modes of action are common with amine-carboxyboranes. Acute toxicity studies in mice showed that both agents were safe in their therapeutic range based on organ weights, histological tissue sections, clinical chemistry values and hematopoietic parameters. 相似文献