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1.
Cp #2Yb (Cp #=C 5H 4(CH 2) 2NMe 2) has been obtained by reaction of YbI 2(THF) 2 with 2 equiv. of C 5H 4(CH 2CH 2NMe 2)K in THF. The X-ray structure analysis shows a bent structure with intramolecular coordination of both nitrogen atoms to ytterbium. The reaction of C 60-fullerene with Cp #2Yb leads to the formation of the fullerenide derivative [Cp #2Yb] 2C 60, which shows an ESR signal in the solid state and in THF solution at room temperature (solid: Δ H = 50 G, G = 1.9992; solution: Δ H = 10 G, G = 2.0001) and a magnetic moment of 3.6 BM. The lutetium fullerenides CpLu(C 60)(DME) (3) and Cp *Lu(C 60)(DME)(C 6H 5CH 3) (4), (Cp = η 5−C 5H 5, Cp * = η 5−C 5Me 5), were obtained by reaction of C 60 with CpLu(C 10H 8) (DME) and Cp *Lu(C 10H 8) (DME) in toluene. Both complexes are paramagnetic (μ eff = 1.4 and 0.9 BM) and exhibit temperature-dependent ESR signals (293 K: g = 1.992 and 2.0002 respectively). 相似文献
2.
The complex C 60Pt[P(OPh) 3] 2 displays C 60 ππ * intraligand bands in the UV-Vis region and a long-wavelength absorption at λ max = 770 nm which is assigned to a metal-to-ligand charge transfer (MLCT) transition from platinum to fullerene. The irradiation of the complex leads to the population of the reactive MLCT state and subsequently to the dissociation (C 60Pt[P(OPh) 3] 2 → C 60 + Pt[P(OPh) 3] 2) in the primary photochemical step. Product formation takes place by the interception of Pt[P(OPh) 3] 2 with suitable scavengers such as CHCl 3 or O 2. 相似文献
3.
The reversible equilibrium conversion under H 2 of [RuCl(dppb) (μ-Cl)] 2 (1) to generate (η 2-H 2) (dppb) (μ-Cl) 3RuCl(dppb) in CH 2Cl 2 (dppb = Ph2P( CH2) 4PPh2) has been studied at 0–25 °C by UV-Vis and 31P{ 1H} NMR spectroscopy, and by stoppe kinetics; the equilibrium constant and corresponding thermodynamic parameters, and the forward and reverse rate constants at 25 °C have been determined. A measured Δ H° value of 0 kJ mol −1 allows for an estimation of an exothermicity of 60 kJ mol −1 for binding an η 2-H 2 at an Ru(II) centre; a Δ S° value of 60 J mol −1 K −1 indicates that in solution 1 contain s coordinated CH 2Cl 2. The kinetic and thermodynamic data are compared to those obtained from a previously studied hydrogenation of styrene catalyzed by 1. Preliminary findings on related systems containing Ph 2P(CH 2) 3PPh 2 and (C 6H 11) 2P(C 6H 11) 2 are also noted. 相似文献
4.
磷酸烯醇式丙酮酸羧化酶(PEPC)通过固定二氧化碳参与光合作用, 是关键的C 4植物光合作用酶。为了揭示高光效转C 4 PEPC基因水稻(Oryza sativa)对干旱胁迫的适应机理, 以高表达转C 4 PEPC水稻(PC)和野生型水稻Kitaake (WT)为供试材料, 在植株的4-5叶期, 使用不同浓度外源CaCl 2溶液处理, 测定在15%聚乙二醇6000 (polyethylene glycol-6000, PEG-6000)胁迫下叶片相对含水量、光合参数、内源钙总含量、叶片总蛋白激酶活性、PEPC酶活性以及相关基因表达和蛋白质含量。结果表明, 0.5 mmol∙L -1 CaCl 2明显提高PC叶片相对含水量(P<0.05), 2 mmol∙L -1和10 mmol∙L -1 CaCl 2则作用不显著, 对WT则影响不显著。不同浓度钙处理对PEG处理PC的净光合速率影响不显著, 而通过维持气孔导度减少水分胁迫。内源总钙浓度的数据显示, 在PEG6000处理下, PC具有维持稳定内源Ca 2+浓度的能力, 过高浓度(10 mmol∙L -1 CaCl 2)钙处理反而降低了PEPC酶活性、PEPC基因表达和可溶性蛋白的含量。 相似文献
5.
By reacting [(C 5Me 5)M(SR F) 2] (forM = Ir, Rf = C 6F 5 (1a) or C 6F 4H- p (1b); for M = Rh, Rf = C 6F 5 (2a) or C 6F 4H- p (2a)) in toluene with Na[AuCl 4], ionic binuclear compounds with the general formula [(C 5Me 5)M(μ-SR F) 2AuCl 2]Cl for M = Ir, R = C 6F 5 (3a) or C 6F 4H- p (3a); for M = Rh, R F = C 6F 5 (4a) or C 6F 4H- p (4b) can be obtained, together with small amounts of [(C 5Me 5) 2Rh 2(μ-SR F)(μ-Cl) 2]Cl (R F = C 6F 5 (5a) or C 6F 4H- p (5b)) as by-products when 2a and 2b were used. 相似文献
6.
A series of borane and monoiodoborane derivatives of bis(diphenylphosphino)alkanes. (C 6H 5) 2P--- (CH 2) n---P(C 6H 5) 2 in which n has values of 2 through 4 has been synthesized. Only compounds with the formulae [(C 6H 5) 2P] 2(CH 2) n · (BH 3) 2 and (C 6H 5) 2P] 2CH 2) n · BH 2I were isolable, the latter being boronium iodides. The compounds were characterized by their melting points, elemental analyses, molar conductivities, infrared spectroscopy, and 1H and 11B nuclear magnetic resonance spectroscopy. The relationship between the length of the carbon chain and the 11B NMR chemical shift is discussed. 相似文献
7.
Panicum milioides, a naturally occurring species with C 4-like Kranz leaf anatomy, is intermediate between C 3 and C 4 plants with respect to photorespiration and the associated oxygen inhibition of photosynthesis. This paper presents direct evidence for a limited degree of C 4 photosynthesis in this C 3-C 4 intermediate species based on: 1. (a) the appearance of 24% of the total 14C fixed following 4 s photosynthesis in 14CO2-air by excised leaves in malate and aspartate and the complete transfer of label from the C4 acids to Calvin cycle intermediates within a 15 s chase in 12CO2-air; 2. (b) pyruvate- or alanine-enhanced light-dependent CO2 fixation and pyruvate stimulation of oxaloacetate- or 3-phosphoglycerate-dependent O2 evolution by illuminated mesophyll protoplasts, but not bundle sheath strands; and 3. (c) NAD-malic enzyme-dependent decarboxylation of C4 acids at the C-4 carboxyl position, C4 acid-dependent O2 evolution, and 14CO2 donation from [4-14C]C4 acids to Calvin cycle intermediates during photosynthesis by bundle sheath strands, but not mesophyll protoplasts.
However, P. milioides differs from C4 plants in that the activity of the C4 cycle enzymes is only 15 to 30% of a C4 Panicum species and the Calvin cycle and phosphoenolpyruvate carboxylase are present in both cell types. From these and related studies (Rathnam, C.K.M. and Chollet, R. (1979) Arch. Biochem. Biophys. 193, 346–354; (1978) Biochem. Biophys. Res. Commun. 85, 801–808) we conclude that reduced photorespiration in P. milioides is due to a limited degree of NAD-malic enzyme-type C4 photosynthesis permitting an increase in pCO2 at the site of bundle sheath, but not mesophyll, ribulosebisphosphate carboxylase-oxygenase. 相似文献
8.
The natural abundance of C 3 and C 4 plants is affected by multiple environmental factors including temperature, moisture balance and atmospheric pCO 2. The relative importance of these factors is a subject of considerable debate, and may vary in different natural ecosystems. Previous studies generally focus on single loess sequences in the Chinese Loess Plateau, and conflicting conclusions on C 4/C 3 have been reached when studying carbon isotope ratios in carbonate and organic matter. In this paper we report a comprehensive carbon isotopic characterization of total organic carbon (TOC) and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the Chinese Loess Plateau (CLP). The five coring sites encompass large gradients of annual mean temperature (9.2–13.9 °C) and precipitation (402–673 mm), allowing us to assess the controlling mechanisms on C 4/C 3 plant ratios. Glacial–interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility. Our results demonstrate that increased C 4/C 3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites. We conclude C 4 abundance increases from the last glacial to the Holocene in response to greater monsoon activity and that the C 4 expression is suppressed in the cold and drier intervals. 相似文献
9.
As part of an investigation to generate optimized drug leads from marine natural pharmacophores for the treatment of neoplastic and infectious diseases, a series of novel isoaaptamine analogs were prepared by coupling acyl halides to the C9 position of isoaaptamine (2) isolated from the Aaptos sponge. This library of new semisynthetic products was evaluated for biological activity against HIV-1, Mtb, AIDS-OI, tropical parasitic diseases, and cancer. Compound 4 showed potent activity against HIV-1 (EC 50 0.47 μg/mL), compound 19 proved to possess remarkable activity against Mycobacterium intracellulare with an IC 50 and MIC value of 0.15 and 0.31 μg/mL, while compounds 4 and 17 possessed anti-leishmanial activity with IC 50 values of 0.1 and 0.4 μg/mL, respectively. Compounds 16 and 17 showed antimalarial activity with EC 50 values of 230 and 240 ng/mL, respectively, and compound 14 exhibited an EC 50 of 0.05 μM against the Leukemia cell line K-562. 相似文献
10.
利用正相硅胶、葡聚糖凝胶Sephadex LH-20和反相C18柱层析等方法,从海绵共附生疣孢菌FIM06031的发酵菌丝体提取液中分离到三个化合物(1~3)。通过波谱方法鉴定其中一个化合物harrucomicin C(1)为新倍半萜,另外两个已知化合物为cyperusol C(2)和Nb-乙酰色胺(3)。活性研究表明harrucomicin C对肿瘤细胞株HepG2、EC109和HeLa具显著增殖抑制活性,其IC50值分别为16.99、25.33μM和34.64μM;cyperusol C对肿瘤细胞HeLa和HepG2增殖抑制作用的IC50值分别为149.99μM和167.78μM。 相似文献
11.
高等植物大多为C 3植物, C 4植物和景天酸代谢(Crassulacean acid metabolism, CAM)植物是由C 3植物进化而来的。C 4途径的多源进化表明, 光合途径由C 3途径向C 4途径的转变相对简单。该文分析研究了植物光合途径的进化前景, 指出C 4植物是从C 3植物进化而来的高光效种类, 且地质时期以来降低的大气CO 2浓度和升高的大气温度以及干旱和盐渍化是C 4途径进化的外部动力。C 3植物的C 4途径的发现说明植物的光合途径并非是一成不变的, C 3和C 4植物的光合特征具有极大的可塑性, 某些环境的变化会引起植物光合途径在C 3和C 4途径之间转变。C 3植物具有的C 4途径是环境调控的产物, 是对逆境的适应性进化结果, 因而光合途径的转变也适用于干旱地区植被的适应性生存机理研究。该文还利用国外最新的C 4光合进化模型介绍了植物在进化C 4途径中所经历的7个重要时期(从分子基础到形态基础、结构基础, 再到物质代谢水平、光合酶活水平, 直到C 3和C 4途径协调运转时期, 最后达到形态与功能最优化阶段), 并结合全球气候变化的特点对国内外相关领域的研究进行了分析, 总结了植物光合途径的适应性转变和进化的研究成果, 为今后的相关工作提出建议。 相似文献
12.
Aims Elevated atmospheric CO 2 has the potential to enhance the net primary productivity of terrestrial ecosystems. However, the role of soil microorganisms on soil C cycling following this increased available C remains ambiguous. This study was conducted to determine how quality and quantity of plant litter inputs would affect soil microorganisms and consequently C turnover. Methods Soil microbial biomass and community structure, bacterial community-level physiological profile, and CO 2 emission caused by different substrate C decomposition were investigated using techniques of biological measurements, chemical and stable C isotope analysis, and BIOLOG-ECO microplates in a semiarid grassland ecosystem of northern China in 2006 and 2007 by mixing three contrasting types of plant materials, C 3 shoot litter (SC 3), C 3 root litter (RC 3), and C 4 shoot litter (SC 4), into the 10- to 20-cm soil layer at rates equivalent to 0 (C 0), 60 (C 60), 120 (C 120) and 240 g C m ?2 (C 240). Important findings Litter addition significantly enriched soil microbial biomass C and N and resulted in changes in microbial structure. Principal component analysis of microbial structure clearly differentiated among zero addition, C 3 -plant-derived litter, and C 4 -plant-derived litter and among shoot- and root-derived litter of C 3 plants; soil microorganisms mainly utilized carbohydrates without litter addition, carboxylic acids with C 3 -plant-derived litter addition and amino acids with C 4 -plant-derived litter addition. We also detected stimulated decomposition of older substrate with C 4 -plant-derived litter inputs. Our results show that both quality and quantity of belowground litter are involved in affecting soil microbial community structure in semiarid grassland ecosystem. 相似文献
13.
[NBu n4] 2[W(C 3Se 5) 3] (C 3Se 52− = 1,3-diselenole-2-selone-4,5- diselenolate(2−)) was prepared by the reaction of Na 2[C 3Se 5] with WCl 6 in ethanol, followed by addition of [NBu n4]Br. The cyclic voltammogram in dichloromethane exhibits two oxidation peaks at −0.04 and +0.03 V (versus SCE). The complex reacted with [Fe(C 5Me 5) 2][BF 4], iodine or [TTF] 3[BF 4] 2 (TTF ·+ = the tetrathiafulvalenium radical cation) in acetonitrile to afford the oxidized complexes [Fe(C 5Me 5) 2] 0.5[W(C 3Se 5) 3], [NBu n4] 0.1[W(C 3Se 5) 3] and [TTF] 0.5[W(C 3Se 5) 3], respectively. Current-controlled electrochemical oxidation of the complex in acetonitrile gave [NBu n4] 0.6[W(C 3Se 5) 3]. The oxidized complexes exhibit electrical conductivities of 4.7×10 −5−1.5×10 −3 S cm −1 at room temperature measured for compacted pellets. Electronic absorption, IR and ESR spectra of these complexes are discussed. 相似文献
14.
The triglyceride compositions of extracts and cornicle secretions of specimens from a range of aphid families were examined by mass spectrometry and found to support earlier evidence that there is little correlation between taxonomic position and chemical constitution. Parasites developing within Myzus persicae preferentially consumed the typical aphid triglycerides which contain hexanoic (C6), sorbic (C6:2), myristic (C14), and palmitic (C16) acid moieties, so that when parasitism was advanced, only triglycerides with three long-chain fatty acids per molecule remained. The adult parasites themselves contained very little triglyceride. Triglycerides of Aphis evonymi and Aphis fabae were similar and varied in composition regularly throughout the year. In the apterous and alate (summer) viviparae, there were equal amounts of myristoyl (C14) and palmitoyl (C16) triglycerides, while in fundatrices and fundatrigeniae (spring forms) myristoyl was predominant. Males collected in autumn resembled the spring forms. However, oviparae and eggs of these and other species differed considerably from the other seasonal forms, in having more hexenoic (C6:1), sorbic (C6:2), and myristoleic (C14:1) acid moieties. 相似文献
15.
Two new dicyanamide bridged 1D polynuclear copper(II) complexes [Cu(L 1){μ 1,5-N(CN) 2}] n (1) [L 1H = C 6H 5C(O)NHNC(CH 3)C 5H 4N] and [Cu(L 2){μ 1,5-N(CN) 2}] n (2) [L 2H=C 6H 5C(O)CHC(CH 3)NCH 2CH 2N(CH 3) 2] have been synthesised and structures of both the complexes and their crystal packing arrangements have been established by X-ray crystallography. For complex 1, a tridentate hydrazone ligand (L 1H) obtained by the condensation of benzhydrazide and 2-acetylpyridine is used, whereas a tridentate Schiff base (L 2H) derived from benzoylacetone and 2-dimethylaminoethylamine is employed for the preparation of complex 2. Variable temperature magnetic susceptibility measurement studies indicate there are weak antiferromagnetic interactions with J values −0.10 and −1.41 cm −1 for 1 and 2, respectively. 相似文献
16.
We have previously shown that azelaic acid, a C 9 dicarboxylic acid, as disodium salt (C 92Na) is capable of inhibiting significantly the hydroxylation of aromatic compounds and the peroxidation of arachidonic acid due to reactive hydroxyl radicals (HO'). In this paper we have investigated the ability of C 92Na to inhibit the oxyradical induced toxicity towards two tumoral cell lines (Raji and IRE 1) and normal human fibroblasts (HF). Oxyradicals were generated either by the addition of polyphenols to the medium, or by direct irradiation of phosphate buffered-saline in which cells were incubated from 15min prior to incubation in normal medium. The effects of C 92Na were compared with those obtained by mannitol (MAN), superoxide dismutase (SOD) and catalase (CAT). C 92Na, MAN, SOD and CAT significantly decreased the polyphenol toxicity towards cell lines cultured up to 24 h. After 48 h of incubation the above compounds lost the capability of protecting cells from polyphenol toxicity. This suggests that the toxic role of oxyradicals (O 2-, H 2O 2, HO .) persists for about 24h and, subsequently other toxic mechanisms must be involved, which are not affected by oxyradical scavengers. SOD and CAT did not show any protective effect on UV induced cytotoxicity, while both C 92Na and MAN were capable of reducing significantly the UV damage towards cell lines, even after 48 h incubation. This can be explained by the fact that UV cytotoxicity depends mainly on the generation of HO', that can be “scavenged” by C 92Na or MAN, but not by SOD or CAT. C 92Na and MAN were not significantly degraded in the period during which they afford protection against HO .. 相似文献
17.
New mixed metal complexes SrCu 2(O 2CR) 3(bdmap) 3 (R = CF 3 (1a), CH 3 (1b)) and a new dinuclear bismuth complex Bi 2(O 2CCH 3) 4(bdmap) 2(H 2O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF 2 and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi 2O 3 at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2 J = 34.0(8) cm −1. Crystal data for 1a: C 27H 51N 6O 9F 9Cu 2Sr/THF, monoclinic space group P2 1/ m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) Å 3, Z = 2; for 1b: C 27H 60N 6O 9Cu 2Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) Å 3, Z = 8; for 2: C 22H 48O 11N 4Bi 2, monoclinic space group P2 1/ c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) Å 3, Z = 4. 相似文献
18.
Photostimulation of N 2 fixation in the blue-green alga Anabaena cylindrica was investigated using monochromatic light and by comparing action spectra of C 2H 2 reduction with that of photosynthetic O 2 evolution. Maximum nitrogenase activity per unit energy was measured at a wavelength which corresponds to the maximum light absorption of chlorophyll a. The action spectrum of C 2H 2 reduction indicates a primary involvement of Photosystem I in N 2 fixation by blue-green algae. 相似文献
19.
Structural analysis of crystallized peripheral (LH2) and core antenna complexes (LH1) of purple bacteria has revealed circular aggregates of high rotational symmetry (C 8, C 9 and C 16, respectively). Quantum-chemical calculations indicate that in particular the waterwheel-like arrangements of pigments should show characteristic structure-sensitive spectroscopic behavior in the near infrared absorption region. Laser-spectroscopic data obtained with non-crystallized, isolated LH2 of Rhodospirillum molischianum are in line with a highly symmetric (C 8) circular aggregate, but deviations have been found for LH2 of Rhodobacter sphaeroides and Rhodopseudomonas acidophila. For both the latter, C-shaped incomplete circular aggregates (as seen only recently in electron micrographs of crystallized LH1–reaction center complexes) may be a suitable preliminary model. 相似文献
20.
The reactions of complex (C 5Me 5)Ir(Cl) (CO) (Me) (1a) with cyclohexylisocyanide and phosphines (L=CyNC, PHPh 2, PMePh 2, PMe 2Ph) give the products of alkyl migratory insertion (C 5Me 5Ir(Cl) (COMe) (L), in toluence or tetrahydrofuran at 323 K or higher temperature. The phenyl analogue (C 5Me 5)Ir(Cl)(CO)(Ph) or the iodide complexes (C 5Me 5)Ir(I) (CO) (R) (R=Me, Ph_are not reactive under the same conditions. The reaction of (C 5Me 5)Ir(Cl)(CO)(Me) with PMePh 2 and PMe 2Ph in acetonitrile yields the chloride substitution product [(C 5Me 5)Ir(CO)(L)(Me)] +Cl −. Kinetic measurements for the reactions of (C 5Me 5)Ir(Cl)(CO)(Me) in toluene are first order in the iridium complex and exhibit a saturation dependence on the incoming donors L. Analysis of the data suggests a two-step process involving (i) rapid formation of a molecular complex [(C 5Me 5)Ir(Cl)(CO)(Me), (L)], in which the structure of 1a is unperturbed within the limits of spectroscopic analysis, and (ii) rate determining methyl migration. The reaction parameters are K for the pre-equilibrium step ( K = 1.5 (CyNC), 7.3 (PHPh 2), 7.1 (PMePh 2) dm 3 mol −1 at 323 K) and k2 for the slow carbon---carbon bond formation ( k2 (10 5) = 6.9 (CyNC), 1.2 (PHPh 2), 1.0 (PMePh 2) s −1 at 323 K). The activation parameters for the methyl migration step in the reaction with PMePh 2 obtained between 308 and 338 K, are Δ H≠ = 106±16 kJ mol −1 and Δ S≠ = − 14±5 J K −1 mol −1. The reaction of 1a with PMePh 2 proceeds at similar rates in tetrahydrofuran ( K = 3.7 dm 3 mol −1, k2 (10 5) = 1.2 s −1, 323 K). The crystal structure of (C 5Me 5)Ir(Cl)(COMe) (PMe 2Ph) has been determined by X-ray diffraction. C 20H 29ClOPIr: Mr = 544.1, monoclinic, P2 1/ n, A = 8.084 (2), B = 9.030(2), C = 28.715 (3) Å, β = 91.41 (3)°, Z = 4, Dc = 1.71 g cm −3, V = 2095.5 Å 3, room temperatyre, Mo K, γ = 0.71069, μ = 65.55 cm −1, F(000) = 1044, R = 0.037 for 2453 independent observed reflections. The complex shows a deformed tetrahedral coordination assuming the η 5-C 5Me 5 molecular fragment as a single coordination site. The iridium-chlorine bond is staggered with respect to two adjacent C(ring)-methyl bonds, while the Ir---P and the Ir---COMe bonds are eclipsed with respect to C(ring)-methyl bonds. 相似文献
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