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671.
Jocelyn Hung Dennis J. Mcnamara Leslie M. Werbel 《Journal of heterocyclic chemistry》1983,20(6):1575-1580
7-Chloro-3-(2,4-dichlorophenyl)-3,4-dihydro-1H-thioxanthene-1,9 (2H)-dione (10), and a variety of analogs and derivatives were prepared as sulfur isosteric analogs of the acridinedione antimalarial agent, floxacrine. The compounds were devoid of antimalarial activity against P. berghei in mice. 相似文献
672.
The First Heteropentanuclear Extended Metal‐Atom Chain: [Ni+Ru25+Ni2+Ni2+(tripyridyldiamido)4(NCS)2] 下载免费PDF全文
Dr. Min‐Jie Huang Dr. Shao‐An Hua Dr. Ming‐Dung Fu Dr. Gin‐Chen Huang Prof. Caixia Yin Chih‐Hung Ko Dr. Ching‐Kuo Kuo Chia‐Hung Hsu Dr. Gene‐Hsiang Lee Kuan‐Yi Ho Dr. Chia‐Hsin Wang Prof. Yaw‐Wen Yang Prof. I‐Chia Chen Prof. Shie‐Ming Peng Prof. Chun‐hsien Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4526-4531
This study develops the first heteropentametal extended metal atom chain (EMAC) in which a string of nickel cores is incorporated with a diruthenium unit to tune the molecular properties. Spectroscopic, crystallographic, and magnetic characterizations show the formation of a fully delocalized Ru25+ unit. This [Ru2]‐containing EMAC exhibits single‐molecule conductance four‐fold superior to that of the pentanickel complex and results in features of negative differential resistance (NDR), which are unobserved in analogues of pentanickel and pentaruthenium EMACs. A plausible mechanism for the NDR behavior is proposed for this diruthenium‐modulated EMAC. 相似文献
673.
Flagella, comprising flagellin proteins, are essential virulence factors for Helicobacter pylori to colonize human stomach mucosa. The flagellin‐associated flaG operon of H. pylori consists of the flaG, fliD, and fliS genes under the control of a σ28‐dependent promoter. The flaG gene is involved in chemotaxis and motility. We cloned, expressed, and purified the H. pylori flaG gene encoding the flagellin protein HpFlaG. Sequence alignment revealed that HpFlaG exhibits low sequence identity with other FlaG proteins. Overall, N‐terminal sequences of FlaG proteins are mostly divergent, and C‐terminal regions might be important for dimer interactions between protein subunits. Here, we report the crystal structure of the N‐terminal truncated protein (NT‐HpFlaG), as determined by multiwavelength anomalous dispersion at a resolution of 2.7 å. The overall structure of NT‐HpFlaG consists of two helices and three strands, folded into a palm‐like conformation. Two monomers strongly interact as a dimer by hydrophobic coiled‐coil interactions. Based on our structure, we suggest that the functional state of HpFlaG is as a dimer. 相似文献
674.
Taxane diterpenoids from seeds of Taxus mairei 总被引:3,自引:0,他引:3
A new 2(3-->20) abeotaxane, taxumairone A (1), and a new cis-p-coumaroyl myo-inositol have been isolated from the seeds of Taxus mairei in addition to taxin B (2), taxinine A, taxuspine X, decinnamoyltaxinine E, 5alpha-cinnamoyloxy-9alpha,10beta,13alpha- triacetoxy-taxa-4(20)11-diene and 5alpha-cinnamoyloxy-2alpha,9alpha,10beta,+ ++13alpha-tetraacetoxy-taxa-4(20)11-diene. The structure of 1 was determined by 2D-NMR spectral analysis and chemical correlation with taxin B (2). Compound 1 exhibited potent cytotoxicity against human colon carcinoma cells with an ED50 of 0.1 microg/ml. 相似文献
675.
Wong KM Zhu X Hung LL Zhu N Yam VW Kwok HS 《Chemical communications (Cambridge, England)》2005,(23):2906-2908
A novel class of luminescent cyclometalated gold(III) alkynyl complexes has been demonstrated to possess EL properties and has been employed in the roles of electrophosphorescent emitters or dopants of organic light-emitting diodes (OLEDs) with high brightness and efficiency. 相似文献
676.
Conversion of Nitric Oxide into Nitrous Oxide as Triggered by the Polarization of Coordinated NO by Hydrogen Bonding 下载免费PDF全文
Chuan‐Hung Chuang Prof. Wen‐Feng Liaw Prof. Chen‐Hsiung Hung 《Angewandte Chemie (International ed. in English)》2016,55(17):5190-5194
Reduction of the {Co(NO)}8 cobalt–nitrosyl N‐confused porphyrin (NCP) [Co(CTPPMe)(NO)] ( 1 ) produced electron‐rich {Co(NO)}9 [Co(CTPPMe)(NO)][Co(Cp*)2] ( 2 ), which was necessary for NO‐to‐N2O conversion. Complex 2 was NO‐reduction‐silent in neat THF, but was partially activated to a hydrogen‐bonded species 2 ??? MeOH in THF/MeOH (1:1, v/v). This species coupling with 2 transformed NO into N2O, which was fragmented from an [N2O2]‐bridging intermediate. An intense IR peak at 1622 cm?1 was ascribed to ν(NO) in an [N2O2]‐containing intermediate. Time–course ESI(?) mass spectra supported the presence of the dimeric [Co(NCP)]2(N2O2) intermediate. Five complete NO‐to‐N2O conversion cycles were possible without significant decay in the amount of N2O produced. 相似文献
677.
The crystal structures of diamagnetic dichloro(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N')-tin(IV) methanol solvate [Sn(2-NCH 3NCTPP)Cl 2.2(0.2MeOH); 6.2(0.2MeOH)] and paramagnetic bromo(2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N',N')-manganese(III) [Mn(2-NCH 3NCTPP)Br; 5] were determined. The coordination sphere around Sn (4+) in 6.2(0.2MeOH) is described as six-coordinate octahedron ( OC-6) in which the apical site is occupied by two transoid Cl (-) ligands, whereas for the Mn (3+) ion in 5, it is a five-coordinate square pyramid ( SPY-5) in which the unidentate Br (-) ligand occupies the axial site. The g value of 9.19 (or 10.4) measured from the parallel polarization (or perpendicular polarization) of X-band EPR spectra at 4 K is consistent with a high spin mononuclear manganese(III) ( S = 2) in 5. The magnitude of axial ( D) and rhombic ( E) zero-field splitting (ZFS) for the mononuclear Mn(III) in 5 were determined approximately as -2.4 cm (-1) and -0.0013 cm (-1), respectively, by paramagnetic susceptibility measurements and conventional EPR spectroscopy. Owing to weak C(45)-H(45A)...Br(1) hydrogen bonds, the mononuclear Mn(III) neutral molecules of 5 are arranged in a one-dimensional network. A weak Mn(III)...Mn(III) ferromagnetic interaction ( J = 0.56 cm (-1)) operates via a [Mn(1)-C(2)-C(1)-N(4)-C(45)-H(45A)...Br(1)-Mn(1)] superexchange pathway in complex 5. 相似文献
678.
Handcuffed designs are a particular case of block designs on graphs. A handcuffed design with parameters v, k, λ consists of a system of ordered k-subsets of a v-set, called handcuffed blocks. In a block {A1, A2,…, Ak} each element is assumed to be handcuffed to its neighbors and the block contains k ? 1 handcuffed pairs (A1, A2), (A2, A1), …, (Ak?1, Ak). These pairs are considered unordered. The collection of handcuffed blocks constitutes a handcuffed design if the following are satisfied: (1) each element of the v-set appears amongst the blocks the same number of times (and at most once in a block) and (2) each pair of distinct elements of the v-set are handcuffed in exactly λ of the blocks. If the total number of blocks is b and each element appears in r blocks the following conditions are necessary for the handcuffed design to exist. (1) λv (v ? 1) = (k ? 1)b. (2) rv = kb. In this paper it is shown that the necessary conditions are also sufficient. 相似文献
679.
H.H. Hung 《Topology and its Applications》2011,158(15):1997-2004
We identify some remnants of normality and call them rudimentary normality, generalize the concept of submetacompact spaces to that of a weakly subparacompact space and that of a weakly? subparacompact space, and make a simultaneous generalization of collectionwise normality and screenability with the introduction of what is to be called collectionwise σ-normality. With these weak properties, we show that,1) on weakly subparacompact spaces, countable compactness = compactness, ω1-compactness = Lindelöfness;2) on weakly subparacompact Hausdorff spaces with rudimentary normality, regularity = normality = countable paracompactness; and3) on weakly subparacompact regular T1-spaces with rudimentary normality, collectionwise σ-normality = screenability = collectionwise normality = paracompactness.The famous Normal Moore Space Conjecture is thus given an even more striking appearance and Worrell and Wicke?s factorization of paracompactness (over Hausdorff spaces) along with Krajewski?s are combined and strengthened. The methodology extends itself to the factorization of paracompactness on locally compact, locally connected spaces in the manner of Gruenhage and on locally compact spaces in that of Tall, and to the factorization of subparacompactness and metacompactness in the genre of Katuta, Chaber, Junnila and Price and Smith and that of Boone, improving all of them. 相似文献
680.
A path cover of a graph G=(V,E) is a set of pairwise vertex-disjoint paths such that the disjoint union of the vertices of these paths equals the vertex set V of G. The path cover problem is, given a graph, to find a path cover having the minimum number of paths. The path cover problem contains the Hamiltonian path problem as a special case since finding a path cover, consisting of a single path, corresponds directly to the Hamiltonian path problem. A graph is a distance-hereditary graph if each pair of vertices is equidistant in every connected induced subgraph containing them. The complexity of the path cover problem on distance-hereditary graphs has remained unknown. In this paper, we propose the first polynomial-time algorithm, which runs in O(|V|9) time, to solve the path cover problem on distance-hereditary graphs. 相似文献