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排序方式: 共有739条查询结果,搜索用时 31 毫秒
41.
The hydrothermal reaction of NiCl2·6H2O, MoO3, 3,4′-bipyridine (3,4′-bpy) and H2O in the mole ratio 1.0:1.0:2.1:1500 yields [Ni(3,4′-bpy)2MoO4]·3H2O (1·3H2O) in 80% yield. The structure of 1·3H2O consists of a three-dimensional coordination polymer {Ni(3,4′-bpy)2}n2n+ with entrained {MoO4}2− tetrahedra and with water molecules of crystallization occupying channels within the bimetallic oxide-ligand framework. Crystal data: C20H16N4O4NiMo·3H2O (1·3H2O), tetragonal P41212, a=13.1866(5) Å, c=29.458(2) Å, V=5122.3(4) Å3, Z=8, Dcalc=1.532 g cm−3. 相似文献
42.
Vladimir B Arion Victor Ch KravtsovJulieta I Gradinaru Yuri A SimonovNicolai V Gerbeleu Janusz LipkowskiJean-Pierre Wignacourt Hervé VezinOlivier Mentré 《Inorganica chimica acta》2002,328(1):123-133
The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H2NNC(SCH3)NH2·HI) in the presence of potassium triflate, followed by addition of M(CH3COO)2·nH2O, where M=Ni, Cu, Zn, afforded [NiLKI3] (2), [NiLK(CF3SO3)] (3), [CuLK(CF3SO3)(CH3OH)] (4) and [(ZnILK)2CH3OH] (5), respectively. Compounds 2-5 have been characterised by X-ray crystallography. IR, electronic, mass, 1H, 13C{1H} and 19F{1H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin-spin interactions, which are mostly dipolar in origin. 相似文献
43.
Hitoshi Kumagai Yoshimi Oka Motoko Akita-TanakaKatsuya Inoue 《Inorganica chimica acta》2002,332(1):176-180
The hydrothermal synthesis, single crystal X-ray structure and magnetic properties of a two-dimensional (2-D) coordination polymer, [Ni4(C6(COO)6)(OH)2(H2O)6] (1), is described. Complex 1 consists of dimer motifs of pseudo octahedral NiO6 linked through μ3-OH to generate one-dimensional (1-D) chains which are further bridged by the mellitate ligands to form non interpenetrated undulating sheet structure. The sheets are further connected by hydrogen bonding interaction to yield a three-dimensional (3-D) structure. The temperature dependence of magnetic susceptibilities revealed the presence of antiferromagnetic interaction between nickel centers. 相似文献
44.
Swiatek-Kozlowska J Brasuń J Łuczkowski M Makowski M 《Journal of inorganic biochemistry》2002,90(3-4):106-112
The study on the binding ability of dehydro-tri- and tetrapeptides has shown that the ,β-double bond has a critical effect on the peptide coordination to metal ions. It may affect the binding of the vicinal amide nitrogens by the electronic effect and stabilize the complex due to steric effects. The (Z) isomer is the most effective in stabilizing of the complexes formed. The presence of large side chain in the dehydroamino acid residue may also be critical for the coordination mode in the metallopeptide systems. 相似文献
45.
Garner B Mellor HR Butters TD Dwek RA Platt FM 《Biochemical and biophysical research communications》2002,290(5):1361-1367
Macrophages synthesize and secrete apolipoprotein E (apoE) constitutively. This process is upregulated under conditions of cholesterol loading. The response to cholesterol is antiatherogenic as it is believed to promote cholesterol efflux from the artery wall. The concentration of lactosyl ceramide (LacCer), a glycosphingolipid recently discovered to regulate cellular signaling, proliferation, and expression of adhesion molecules, is also increased in atherosclerotic tissues. Here we have investigated the effect of exogenous LacCer on macrophage apoE levels. We show that increasing macrophage LacCer levels sevenfold led to reductions in cellular and secreted apoE (15 and 30%, respectively, over a 24-h period) as determined by enzyme-linked immunosorbent assay. A similar effect was also induced by glucosyl ceramide (GlcCer) but not by ganglioside species. When macrophages were converted to cholesterol-loaded foam cells by incubation with acetylated LDL, the resulting increase in cellular apoE levels was inhibited by 26% when the cells were subsequently enriched with LacCer. After metabolic labeling of cellular glycosphingolipids with [14C]palmitate, we also discovered that high-density lipoprotein (HDL) stimulates the efflux of glycosphingolipids from foam cells. These data imply that LacCer and GlcCer may be proatherogenic due to the suppression of macrophage apoE production. Furthermore, the efflux of glycosphingolipids from macrophage foam cells to HDL could indicate a potential pathway for their removal from the artery wall and subsequent delivery to the liver. 相似文献
46.
Hoeks FW Boon LA Studer F Wolff MO van der Schot F Vrabél P van der Lans RG Bujalski W Manelius A Blomsten G Hjorth S Prada G Luyben KCh Nienow AW 《Journal of industrial microbiology & biotechnology》2003,30(2):118-128
Foam disruption by agitation—the stirring as foam disruption (SAFD) technique—was scaled up to pilot and production scale
using Rushton turbines and an up-pumping hydrofoil impeller, the Scaba 3SHP1. The dominating mechanism behind SAFD—foam entrainment—was
also demonstrated at production scale. The mechanistic model for SAFD defines a fictitious liquid velocity generated by the
(upper) impeller near the dispersion surface, which is correlated with complete foam disruption. This model proved to be scalable,
thus enabling the model to be used for the design of SAFD applications. Axial upward pumping impellers appeared to be more
effective with respect to SAFD than Rushton turbines, as demonstrated by retrofitting a 12,000 l bioreactor, i.e. the triple
Rushton configuration was compared with a mixed impeller configuration from Scaba with a 20% lower ungassed power draw. The
retrofitted impeller configuration allowed 10% more broth without risking excessive foaming. In this way a substantial increase
in the volumetric productivity of the bioreactor was achieved. Design recommendations for the application of SAFD are given
in this paper. Using these recommendations for the design of a 30,000 l scale bioreactor, almost foamless Escherichia coli fermentations were realised.
Electronic Publication 相似文献
47.
Nickel uptake and utilization by microorganisms 总被引:19,自引:0,他引:19
Nickel is an essential nutrient for selected microorganisms where it participates in a variety of cellular processes. Many microbes are capable of sensing cellular nickel ion concentrations and taking up this nutrient via nickel-specific permeases or ATP-binding cassette-type transport systems. The metal ion is specifically incorporated into nickel-dependent enzymes, often via complex assembly processes requiring accessory proteins and additional non-protein components, in some cases accompanied by nucleotide triphosphate hydrolysis. To date, nine nickel-containing enzymes are known: urease, NiFe-hydrogenase, carbon monoxide dehydrogenase, acetyl-CoA decarbonylase/synthase, methyl coenzyme M reductase, certain superoxide dismutases, some glyoxylases, aci-reductone dioxygenase, and methylenediurease. Seven of these enzymes have been structurally characterized, revealing distinct metallocenter environments in each case. 相似文献
48.
The complex compound K2[Ni(cit)(H2O)2]2·4H2O (cit = triionized citrate ion) seems to be a good model for the investigation of Ni(II)/citrate interactions that are of
interest in relation to nickel metabolism and bioaccumulation. Its infrared and Raman spectra were recorded and analyzed on
the basis of its structural peculiarities. The magnetic susceptibility, investigated in the temperature range between 1.9
and 300 K, shows the absence of magnetic interactions between the two metal centers present in this structure. 相似文献
49.
The aim of this work was to study the absorption of nickel chloride in rats by means of the intestinal perfusion in situ technique at nickel concentrations of 1, 5, 10, 25, and 100 mg/L. Active transport and facilitated diffusion seem to play
an important role in the intestinal absorption of nickel at concentrations≤10 mg/L. At higher concentrations, the absorption
rate would be limited by saturation of the carriers. The distribution of the absorbed nickel was studied by intestinal perfusion
of a 10-mg Ni/L solution for 30 or 60 min. Both in concentration and amount, the jejunum showed the higher values of absorbed
nickel, followed by the kidneys and liver. When all of the collected organs (brain, heart, liver, lungs, spleen, kidneys,
and testicles) and blood, but not the small intestine, are analyzed following a 60-min perfusion, it was found that 1% of
the initial concentration had passed through the intestinal barrier. 相似文献
50.
J. Štěpánek Jozef Kowalewski J. Lang Peter Mojzeš 《Journal of biological inorganic chemistry》1998,3(5):543-556
The interaction of Ni(II) ions with adenine mononucleotides (5′-AMP, 3′-AMP, 2′-AMP, 2′,3′-cAMP, 3′,5′-cAMP) was studied
in aqueous solution using Raman spectroscopy and 13C and 31P NMR paramagnetic relaxation measurements. Macrochelate structures were observed to form for all non-cyclic AMPs, with increasing
stability in the series: 3′-AMP < 2′-AMP < 5′-AMP. N7 of adenine was found to be the key site of the Ni(II)-adenine interaction
for all non-cyclic AMPs. For 2′-AMP, an alternative binding to the pyrimidine ring may also exist. The dependence of Raman
spectra on AMP and Ni(II) concentration confirmed the existence of a stable 1 : 2 Ni(II)-(5′-AMP) complex, besides the 1 : 1
complexes. In this complex, the adenine moieties of both 5′-AMP molecules are situated close to Ni(II), and their relative
orientations with respect to the cation are very similar. The paramagnetic relaxation enhancements of the carbons indicate
that the nickel ion is not located in the plane of the adenine units, but that the line connecting Ni(II) and N7 deviates
strongly from the adenine planes. Phosphates are outer-sphere coordinated by the cation. Findings from both methods have led
us to propose possible global architectures of the complex.
Received: 26 June 1998 / Accepted: 22 July 1998 相似文献