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991.
Summary The chromium(V) complex [bipyH2][CrOCl5] reacts with MeCN to yield the octahedral chromium(III) complex [CrCl3(bipy)(NCMe)], the nitrile ligand of which can be replaced by other ligands to give [CrCl3(bipy)L] complexes (L = py, pyO, and Ph3PO). However, reactions of [bipyH2]-[CrOCl5] with higher nitriles RCN (R = Et, n-Pr, Ph, or PhCH2) or with MeNO2 all lead to the isolation of [CrCl3(bipy)]n (n most probably being 2), which may also be prepared by thermal decomposition of [CrCl3(bipy)(NCMe)]. 相似文献
992.
We perform ab initio molecular dynamics simulations of the aqueous formate ion. The mean number of water molecules in the first solvation shell, or the hydration number, of each formate oxygen is found to be consistent with recent experiments. Our ab initio pair correlation functions, however, differ significantly from many classical force field results and hybrid quantum mechanics/molecular mechanics predictions. They yield roughly one less hydrogen bond between each formate oxygen and water than force field or hybrid methods predict. Both the BLYP and PW91 exchange correlation functionals give qualitatively similar results. The time dependence of the hydration numbers are examined, and Wannier function techniques are used to analyze electronic configurations along the molecular dynamics trajectory. 相似文献
993.
Weitzer M Schindler S Brehm G Schneider S Hörmann E Jung B Kaderli S Zuberbühler AD 《Inorganic chemistry》2003,42(6):1800-1806
At low temperatures, the mononuclear copper(I) complex of the tetradentate tripodal aliphatic amine Me(6)tren (Me(6)tren = tris(2-dimethylaminoethyl)amine) [Cu(I)(Me(6)tren)(RCN)](+) first reversibly binds dioxygen to form a 1:1 Cu-O(2) species which further reacts reversibly with a second [Cu(I)(Me(6)tren)(RCN)](+) ion to form the dinuclear 2:1 Cu(2)O(2) adduct. The reaction can be observed using low temperature stopped-flow techniques. The copper superoxo complex as well as the peroxo complex were characterized by resonance Raman spectroscopy. The spectral characteristics and full kinetic and thermodynamic results for the reaction of [Cu(I)(Me(6)tren)(RCN)](+) with dioxygen are reported. 相似文献
994.
THE EFFECT OF IRON ON THE DISTRIBUTION OF SUPEROXIDE AND HYDROXYL RADICALS AS SEEN BY SPIN TRAPPING AND ON THE SUPEROXIDE DISMUTASE ASSAY 总被引:8,自引:0,他引:8
Garry R. Buettner Larry W. Oberley Susan W. H. Chan Leuthauser 《Photochemistry and photobiology》1978,28(4-5):693-695
Abstract— Using the spin trap 5,5-dimethyl-1-pyrroline-1-oxide we have demonstrated the presence of OH in the xanthine-xanthine oxidase system when iron and/or iron-EDTA (ethylenediamine-tetraacetic acid) is present. With increasing iron (or iron-EDTA) concentration the intensity of the O2 - spin adduct decreased while that of OH increased. However, use of diethylenetriaminepentaacetic acid (DETAPAC) as a metal chelator in the reaction mixture suppressed the OH spin adduct signal while maintaining the intensity of the signal from the O2 - spin adduct.
Use of EDTA to eliminate the interfering effects of metal ions in the superoxide dismutase assay employing xanthine oxidase and nitroblue tetrazolium introduces an artifact from the iron present. The interference in the assay from metal ions, including iron, can be eliminated with use of DETAPAC as a metal chelator. Thus, it is possible to make comparisons of measured superoxide dismutase activities even when there are variations in the amount of iron present in the samples. 相似文献
Use of EDTA to eliminate the interfering effects of metal ions in the superoxide dismutase assay employing xanthine oxidase and nitroblue tetrazolium introduces an artifact from the iron present. The interference in the assay from metal ions, including iron, can be eliminated with use of DETAPAC as a metal chelator. Thus, it is possible to make comparisons of measured superoxide dismutase activities even when there are variations in the amount of iron present in the samples. 相似文献
995.
Agapie T Schofer SJ Labinger JA Bercaw JE 《Journal of the American Chemical Society》2004,126(5):1304-1305
A system for catalytic trimerization of ethylene utilizing CrCl3(THF)3 and a diphosphine ligand PNPOMe [= (o-MeO-C6H4)2PN(Me)P(o-MeO-C6H4)2] has been investigated. The coordination chemistry of chromium with PNPOMe has been explored, and (PNPOMe)CrCl3 and (PNPOMe)CrPh3 (3) have been synthesized by ether displacement from chromium(III) precursors. Salt metathesis of (PNPOMe)CrCl3 with o,o'-biphenyldiyl Grignard affords (PNPOMe)Cr(o,o'-biphenyldiyl)Br (4). Activation of 3 with H(Et2O)2B[C6H3(CF3)2]4 or 4 with NaB[C6H3(CF3)2]4 generates a catalytic system and trimerizes a 1:1 mixture of C2D4 and C2H4 to give isotopomers of 1-hexene without H/D scrambling (C6D12, C6D8H4, C6D4H8, and C6H12 in a 1:3:3:1 ratio). The lack of crossover supports a mechanism involving metallacyclic intermediates. The mechanism of the ethylene trimerization reaction has also been studied by the reaction of trans-, cis-, and gem-ethylene-d2 with 4 upon activation with NaB[C6H3(CF3)2]4. 相似文献
996.
Chuanming Duan Steven Rosen James Towt Susan Rouse Haleema Subuhi Salvatore J. Salamone 《Applied biochemistry and biotechnology》1998,69(3):217-224
Carbohydrate-deficient transferrin (CDT) molecules are transferrin isoforms that lack one or both of the carbohydrate groups
attached to a normal human transferrin molecule. CDT has been reported to be a sensitive and specific marker for diagnosing
alcoholism. This report demonstrates the in vitro generation of CDT molecules that can potentially be used as the standard
in measuring CDT concentrations. This was achieved by deglycosylation of human transferrin with the enzyme Endo-β-N-acetylglucosaminidase F2 (Endo-F2). The enzyme was immobilized on sepharose beads, which were packed into a column. The immobilization of the enzyme not only
eliminated the Endo-F2 contamination of CDT, but also rendered the enzyme suitable for repetitive use. In this manner, it was possible to obtain
at least 200 mg of CDT over a period of more than 3 mo, without any noticeable decrease of enzyme activity, using only 3.0
μg of enzyme. This proved to be an efficient method for generating CDT. 相似文献
997.
Piña IC Gautschi JT Wang GY Sanders ML Schmitz FJ France D Cornell-Kennon S Sambucetti LC Remiszewski SW Perez LB Bair KW Crews P 《The Journal of organic chemistry》2003,68(10):3866-3873
Four novel bisulfide bromotyrosine derivatives, psammaplins E (9), F (10), G (11), and H (12), and two new bromotyrosine derivatives, psammaplins I (13) and J (14), were isolated from the sponge Pseudoceratina purpurea, along with known psammaplins A (4), B (6), C (7), and D (8) and bisaprasin (5). The structures of psammaplins E (9) and F (10), which each contain an oxalyl group rarely found in marine organisms, were determined by spectroscopic analysis. Compounds 4, 5, and 10 are potent histone deacetylase inhibitors and also show mild cytotoxicity. Furthermore, compounds 4, 5, and 11 are potent DNA methyltransferase inhibitors. The biogenetic pathway previously proposed for the psammaplins class is also revisited. 相似文献
998.
Zhenyu Wang Daniel Fritsch Stefan Berendts Martin Lerch Joachim Breternitz Susan Schorr 《Chemical science》2021,12(24):8493
Ternary II–IV–N2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III–V materials to ternary II–IV–N2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure–property relationships in this emerging class of materials.Combining chemical analyses with detailed structural work, we decipher the reaction pathway in the ammonolysis of Zn2GeO4 towards ZnGeN2. 相似文献
999.
A recently developed commercial rapid test kit (MIST Alert) was assessed for determination of the presence of paralytic shellfish poisoning (PSP) toxins in shellfish. Several commercially important shellfish species obtained from the UK shellfish toxin monitoring program, containing a range of total PSP toxicities as determined by the mouse bioassay (MBA), were tested. The kit detected toxin in all samples containing the European Community tolerance level of 80 microg saxitoxin (STX) equivalents/100 g shellfish flesh as determined by the MBA. With one exception, the kit detected toxin in all samples that contained >40 microg STX equivalents/100 g according to the MBA. Among samples in which the MBA did not detect toxin, the kit disagreed in 25% of the tests, although further analysis by liquid chromatography (LC) and MBA of some samples confirmed the presence of toxins. These results suggest that MIST Alert may be suitable as an initial screen for PSP toxins as part of routine monitoring programs, thereby greatly reducing the number of MBAs. Trials were also performed by nonscientific personnel to evaluate the ease of use and interpretation of results obtained by MIST Alert. The results indicated that the kits could be readily used and accurately interpreted by individuals with no technical or scientific background. 相似文献
1000.
Diego T. Gomez Lawrence R. Pratt David M. Rogers Susan B. Rempe 《Molecules (Basel, Switzerland)》2021,26(11)
With a longer-term goal of addressing the comparative behavior of the aqueous halides F, Cl, Br, and I on the basis of quasi-chemical theory (QCT), here we study structures and free energies of hydration clusters for those anions. We confirm that energetically optimal clusters, with X = Cl, Br, and I, exhibit surface hydration structures. Computed free energies, based on optimized surface hydration structures utilizing a harmonic approximation, typically (but not always) disagree with experimental free energies. To remedy the harmonic approximation, we utilize single-point electronic structure calculations on cluster geometries sampled from an AIMD (ab initio molecular dynamics) simulation stream. This rough-landscape procedure is broadly satisfactory and suggests unfavorable ligand crowding as the physical effect addressed. Nevertheless, this procedure can break down when , with the characteristic discrepancy resulting from a relaxed definition of clustering in the identification of clusters, including ramified structures natural in physical cluster theories. With ramified structures, the central equation for the present rough-landscape approach can acquire some inconsistency. Extension of these physical cluster theories in the direction of QCT should remedy that issue, and should be the next step in this research direction. 相似文献