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排序方式: 共有73条查询结果,搜索用时 218 毫秒
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.
Robert L Waterland Kerwin D Dobbs Amy M Rinehart Andrew E Feiring Robert C Wheland Bruce E Smart 《Journal of fluorine chemistry》2003,122(1):37-46
In its continuing quest for smaller length scales, the electronics industry plans to introduce 157 nm as the next lithographic wavelength. Accordingly, there is a pressing need to develop photoresists that are more transparent, and pellicles that are both more transparent and more durable. With the advent and popularization of time-dependent density functional theory (TD-DFT), we now have a practical quantum chemical method for calculating excitation energies and transition moments in the vacuum ultraviolet (VUV) which can greatly assist in the scouting of highly transparent materials. We have performed TD-DFT calculations for a broad variety of fluorinated molecules and we will report calculated VUV photoabsorption spectra for a large family of model fluorohexanes. These calculations, which span a range from 1-fluorohexane to CH3CF2CF2CF2CF2CH3, illustrate some of the principles one may use to design low absorption polymeric materials. 相似文献
3.
4.
Kenneth L. Rinehart 《Trends in analytical chemistry : TRAC》1983,2(1):10-14
Fast atom bombardment mass spectrometry (FABMS) is a powerful new structural tool. Ionization is effected by bombarding a glycerol matrix with neon or argon atoms of 5–10 KeV energy. Positive and negative secondary ions are sputtered from the surface and can be detected for inorganic ion clusters to mass 25 800 and biologically important compounds to mass 5 700. FABMS is especially valuable in determining the sequence of amino acids in polypeptides. 相似文献
5.
The structures of two saponins, thyonosides A and B, isolated from the holothurian Thyone aurea collected in Namibia, were elucidated by 1D and 2D NMR (1H, 13C, 1H-1H COSY, 1H-1H J-resolved, TOCSY, HMQC, HMBC and NOESY). The two compounds have the same aglycon but different oligosaccharidic chains. Thyonoside A has a 3-O-methyl-β-d-xylopyranosyl-(1→3)-6-O-sodium sulphate-β-d-glucopyranosyl-(1→4)-β-d-quinovopyranosyl-(1→2)-4-O-sodium sulphate-β-d-xylopyranosyl chain, and thyonoside B a 3-O-methyl-β-d-xylopyranosyl-(1→4)-β-d-xylopyranosyl-(1→4)-β-d-quinovopyranosyl-(1→2)-4-O-sodium sulphate-β-d-xylopyranosyl chain. The holostane-type aglycon features an endocyclic double bond at position 7-8, a double bond at position 25-26 and a β-acetoxy group at C16. 相似文献
6.
Mark L. Proefke Kenneth L. Rinehart 《Journal of the American Society for Mass Spectrometry》1992,3(5):582-589
Fast atom bombardment combined with mass spectrometry (FAB/MS), high resolution FAB/MS, FAB tandem mass spectrometry (MS/MS), and gas chromatography/mass spectrometry (GC/MS) were used to determine the composition of the resinous material recovered from the wrappings of an Egyptian mummy believed to be from the Roman period (100–350 A.D.). FAB/MS and MS/MS studies identified several oxidation products of abietic acid as the principal resin components, indicating that one or more species of coniferous trees were used by the Egyptians as a source of the resin. GC/MS studies also identified several n-alkanes with carbon numbers from C19 to C33 in the sample. The relative amounts of these n-alkanes, along with characteristic trace metals, indicate that bitumen, an asphalt native to the region, was added to the resin. The presence of this ancient source of carbon in this sample explains the inconsistent date assigned to the mummy by carbon-14 analysis. 相似文献
7.
A new nitro-containing metabolite, spectinabilin, was isolated from the crude streptovaricin complex produced by Streptomyces spectabilis. The structure was determined by degradation studies and spectral properties. A possible biosynthetic pathway of the metabolite is discussed in relation to the biosynthesis of the streptovaricins. 相似文献
8.
Dr. Michael Georg Hoesl M. Sc. Stefan Oehm Dr. Patrick Durkin Dr. Elise Darmon Dr. Lauri Peil Dr. Hans‐Rudolf Aerni Prof. Dr. Juri Rappsilber Prof. Dr. Jesse Rinehart Prof. Dr. David Leach Prof. Dr. Dieter Söll Prof. Dr. Nediljko Budisa 《Angewandte Chemie (International ed. in English)》2015,54(34):10030-10034
We have changed the amino acid set of the genetic code of Escherichia coli by evolving cultures capable of growing on the synthetic noncanonical amino acid L ‐β‐(thieno[3,2‐b]pyrrolyl)alanine ([3,2]Tpa) as a sole surrogate for the canonical amino acid L ‐tryptophan (Trp). A long‐term cultivation experiment in defined synthetic media resulted in the evolution of cells capable of surviving Trp→[3,2]Tpa substitutions in their proteomes in response to the 20 899 TGG codons of the E. coli W3110 genome. These evolved bacteria with new‐to‐nature amino acid composition showed robust growth in the complete absence of Trp. Our experimental results illustrate an approach for the evolution of synthetic cells with alternative biochemical building blocks. 相似文献
9.
Howard MD Lu X Rinehart JJ Jay M Dziubla TD 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1964-1971
As the physicochemical characteristics of solid lipid nanoparticles (SLNs) play a critical role in their success, it is important to understand how the materials and process used in their preparation affect these properties. In this study, two stearyl alcohol-based formulations were prepared using nanotemplate engineering technology and characterized. Both formulations were of a small particle size (<100 nm), ellipsoidal shape, and low polydispersity. (1)H NMR spectroscopy confirmed that the SLNs have the expected solid core structure and PEGylated surface. Analysis of the bulk materials indicated that a number of complex interactions are present among the SLN components, including a eutectic between stearyl alcohol and Brij 78. The decreased crystallinity resulting from these interactions may allow for enhanced drug loading. Physiological stability was identified and confirmed as a potential problem due to the low melting point of the eutectic. However, it is expected that with appropriate formulation modifications nanotemplate engineered SLNs will possess the properties necessary for a successful drug delivery system. 相似文献
10.