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81.
Identification and analysis of the core biosynthetic machinery of tubulysin, a potent cytotoxin with potential anticancer activity 总被引:4,自引:0,他引:4
Myxobacteria are well known for their biosynthetic potential, especially for the production of cytotoxic compounds with potential anticancer activities. The tubulysins are currently in preclinical development. They are produced in very low quantities, and genetic manipulation of producing strains has never been accomplished. We report the development of a mariner-based transposon mutagenesis system for Angiococcus disciformis An d48. Extracts from a library of 1200 mutants were analyzed for the presence of tubulysin by a microscopic cell nucleus fragmentation bioassay. The transposition sites of four tubulysin-negative mutants were identified by vector recovery, which led to the identification and the sequencing of the corresponding core biosynthetic gene locus. Sequence analysis of more than 80,000 bp reveals an unusual multimodular hybrid polyketide synthase/peptide synthetase assembly line with a variety of unprecedented features. 相似文献
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83.
The thiotungstate [Et4N]2[OW(WS4)2], [Et4N]2.1, containing the linear [[S2W(VI)(mu-S)2]2W(IV)=O] core, was prepared from [Et4N]2[WS4] in the presence of the sulfide scavenger Cd2+. Addition of 1,2-bis(o-diphenylphosphinophenyl)ethane (diphosphine) and Cu+ or Ag+ to solutions of 1 in MeCN/DMF led to coordination of the (diphosphine)Cu/Ag fragments to the terminal sulfido ligands of 1, yielding novel linear pentanuclear, heterometallic clusters [mu-[OW(IV)(DMF)(W(VI)S4)2][M(diphosphine)]2], 2 (M = Cu) and 3 (M = Ag). Along with 2, the trinuclear cluster [[mu-(W(VI)S4)[Cu(diphosphine)(2)]], 4, was also obtained. The molecular and crystal structures of [Et4N]2.1, 2.MeCN, 3.MeCN, and 4.2MeCN.CH2Cl2 have been determined. 相似文献
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Tumarkin E Nie Z Park JI Abolhasani M Greener J Sherwood-Lollar B Günther A Kumacheva E 《Lab on a chip》2011,11(20):3545-3550
We report a microfluidic (MF) approach to studies of temperature mediated carbon dioxide (CO(2)) transfer between the gas and the liquid phases. Micrometre-diameter CO(2) bubbles with a narrow size distribution were generated in an aqueous or organic liquid and subsequently were subjected to temperature changes in the downstream channel. In response to the cooling-heating-cooling cycle the bubbles underwent corresponding contraction-expansion-contraction transitions, which we term 'bubble breathing'. We examined temperature-controlled dissolution of CO(2) in four exemplary liquid systems: deionized water, a 0.7 M aqueous solution of NaCl, ocean water extracted from Bermuda coastal waters, and dimethyl ether of poly(ethylene glycol), a solvent used in industry for absorption of CO(2). The MF approach can be extended to studies of other gases with a distinct, temperature-dependent solubility in liquids. 相似文献
87.
[PPh(4)][EI(4)] (E=As, Sb, Bi) salts were reacted with four and five equivalents of AgN(3) to form tetraazidopnictates and pentaazidopnictates of the type [PPh(4)][E(N(3))(4)] and [PPh(4)](2)[E(N(3))(5)], respectively. The synthesis of [PPh(4)][P(N(3))(4)] was also attempted from the reaction of P(N(3))(3) with [PPh(4)]N(3), but it yielded only the starting materials. Herein, we report the synthesis and structure elucidation of [PPh(4)][E(N(3))](4) (E=As, Sb) and pentaazidobismuthate, stabilized as the dimethyl sulfoxide (DMSO) anion adduct, [PPh(4)](2)[Bi(N(3))(5)(dmso)]. Successive anion formation along the series E(N(3))(3)+nN(3)(-) (n=1-3) and E(N(3))(5)+N(3)(-) was studied by density functional theory. 相似文献
88.
New Ternary Clathrate Compounds in the Systems Barium–Indium/Zinc/Cadmium–Germanium: Zintl Compounds with Phase Width? By systematic investigations in the systems barium–indium/zinc/cadmium–germanium we found a couple of new electrovalent ternary compounds with A8X46 clathrate (I) type structures. They crystallize cubically in space-group Pm3n. For Ba8In16Ge30 (a = 1 075.8 pm), Ba8Zn8Ge38 (a = 1 082.0 pm) and Ba8Cd8Ge38 (a = 1 096.0 pm) the structures were verified by X-ray single crystal diffraction data. According to valence and bounding distances the new clathrates should be Zintl compounds. Measurements of the temperature dependence of the electrical resistivity proved, that they are indeed semiconductors. A part of the 2B/3B metal atoms can be substituted by germanium. Charge balance will be retained by creation of vacancies in the A8X46 type structures. By phase analysis the limits of the composition range were determined as Ba8In4Ge9[]3Ge30 (a = 1 084.9 pm), Ba8Zn4Ge10[]2Ge30 (a = 1 073.6 pm) and Ba8Cd4Ge10[]2Ge30 (a = 1 082.0 pm). 相似文献
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90.
Waldmann T Künzel D Hoster HE GroSS A Behm RJ 《Journal of the American Chemical Society》2012,134(21):8817-8822
The reaction of O(2) with an adlayer of the oligopyridine 2-phenyl-4,6-bis(6-(pyridine-2-yl)-4-(pyridine-4-yl)-pyridine-2-yl)pyrimidine (2,4'-BTP), adsorbed on the (111) surfaces of silver and gold and on HOPG--which can be considered as a model system for inorganic|organic contacts--was investigated by fast scanning tunneling microscopy (video STM) and dispersion corrected density functional theory (DFT-D) calculations. Only on Ag(111), oxidation of the 2,4'-BTP adlayer was observed, which is related to the fact that under the experimental conditions O(2) adsorbs dissociatively on this surface leading to reactive O adatoms, but not on Au(111) or HOPG . There is a distinct regiospecifity of the oxidation reaction caused by intermolecular interactions. In addition, the oxidation leads to a chiral ordering. The relevance of these findings for reactions involving organic monolayers is discussed. 相似文献