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1.
The absorption spectra of Ru(2,2′-bipyridine)2 (2,2′-bipyridine-4,4′-dicarboxylic acid)2+ (I) and its diethyl ester (II) are closely related and are both significantly different from the spectra of the mono-protonated (Ia) and deprotonated (Ib) complexes. Luminescence polarization measurements show that for I and II the luminescent states have the transferred electron in the bipy-4,4′(COOH)2 and bipy-4,4′(COOEt)2 ligands, respectively, rather than in the unsubstituted bipy ligands. 相似文献
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Crosslinked polymer beads containing regions of acidic and basic groups are the preferred structures for the efficient operation of a thermally regenerable ion-exchange process. Such systems can be prepared by various methods. Here the approach of using polymers and copolymers containing photo-labile groups as grafting sites is described. The polymers studied were polytriallylamine hydrochloride (polyTAA) and copolymers of propyldiallylamine hydrochloride (PDAA) and allyl benzoin methyl ether (ABME), of ABME and acrylic acid (AA), and of ABME and methyl acrylate (MA). The maximum amount of photografting of MA onto polyTAA was 12%. Very little photografting of MA onto PDAA:ABME copolymers was obtained. Photografting of TAA to AA:ABME and to MA:ABME copolymers occurred readily by using radiation of 360 nm wavelength, with the best yields of photografted polymer being about 60% when a MA:ABME copolymer was irradiated in a suspension. The effect of suspending medium, stirring rate, irradiation time, irradiation intensity, solvent, solids concentration, percentage of ABME in the MA:ABME copolymer, additional crosslinkers, surfactants, and the acid:base ratio in the hy-drolyzed resin prepared by photografting TAA onto MA:ABME copolymers on the yield, physical strength, shape, and ion-exchange properties of the resins is reported. 相似文献
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Synthesis and Investigation of Aminosulphur Trifluorides and of a Hydrolysis Product 1-(Fluorooxothio)-2,5-dihydropyrrole The reaction of previously unknown (trimethylsilyl)amines with sulphur tetrafluoride gives some new aminosulphurtrifluorides. Experiments to cleaver 1-(Trifluorothio)-2,5-dihydropyrrole and 1-(trifluorothio)pyrrolidin into butadiene and ethylene respectively and NSF3 by way of a chelotrope cycloelimination were unsuccessful. 1H-NMR and 19F-NMR spectra revealed the nitrogen in the aminosulphur trifluorides must be regarded sp3 hybridized rather than sp2. 相似文献
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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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Atilla-Gokcumen GE Bedigian AV Sasse S Eggert US 《Journal of the American Chemical Society》2011,133(26):10010-10013
Although cells undergo dramatic shape changes during cytokinesis, the role of the plasma membrane and lipids is poorly understood. We report that inactivation of glucosyl ceramide synthase (GCS), either by RNAi or with the small molecule PPMP, causes failure of cleavage furrow ingression. Using mass-spectrometry-based global lipid profiling, we identify individual lipids that are enhanced or depleted due to GCS inhibition. We show that GCS inhibition results in the mislocalization of actin and the ERM proteins, key cytoskeletal proteins that connect the plasma membrane to the actin cortex. Our data suggest that ceramides participate in mediating the interactions between the membrane and the cortex. 相似文献
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Singlet and triplet energy transfer processes in [Ru(bipy)2(4-methyl-4′-(2-arylethyl)-2,2′-bipyridine)]2+ have been investigated, where ARYL = 2-naphthyl (Ru-Naph), 9-anthryl (Ru-Anth) and 1-pyrenyl (Ru-Pyrene). In each case fluorescence from the aromatic chromophore is quenched by intramolecular energy transfer to Ru(bipy)32+ whereas emission from the Ru(bipy)32+ moiety is controlled by the relative energy of its 3MLCT state and the pendant arene triplet states. Consequently 3MLCT emission is observed for Ru-Naph whereas it is fully quenched for Ru-Anth. When the two states are isoenergetic (e.g. Ru-Pyrene) a long-lived 3MLCT emission is observed which delays with the same lifetime as the pyrene triplet state (5.23 μs). 相似文献
10.
Hans-Eckard Sasse und Ulf König 《Fresenius' Journal of Analytical Chemistry》1984,319(6-7):872-876
Zusammenfassung Oberflächen der Halbleiter InP, GaAs und GaAlAs wurden untersucht. Über naßchemische präparative Einflüsse auf die Belegung von InP und GaAs mit Sauerstoff und Kohlenstoff wird berichtet. Bei GaAs hinterließ eine Reinigung mit Trichlorethylen gefolgt von HCl keine nachweisbaren Oxidationsprodukte. Bei InP ist eine Reinigungsfolge, bestehend aus Chloroform, H2SO4: H2O2:H2O und KOH, empfehlenswert zum Erzielen minimaler Kohlenstoffbelegung. Wenig Sauerstoff ist nachweisbar nach einer HF-Behandlung. Außerdem wird die Wirksamkeit von Passivierungsschichten zum Schutz der Halbleiter GaAs und GaAlAs gegen Umwelteinflüsse geprüft. Bei höheren Temperaturen diffundiert Sauerstoff durch die Passivierung und oxidiert den Halbleiter. Es bilden sich Zwischenschichten aus Ga2O3 bzw. Al2O3 und As. Vermeidbar ist dies nur durch eine reduzierende (H2) oder inerte (Ar) Atmosphäre.
ESCA investigation of the oxidation of III-V semiconductors
Summary Surfaces of the semiconductors InP, GaAs and GaAlAs are investigated. Influences of the wet chemical preparation of InP and GaAs on the surface contamination by oxygen and carbon are reported. After treatment with trichloroethylene followed by HCl, no oxidation products could be detected on GaAs. In the case of InP, a successive treatment with CHCl3, H2SO4:H2O2:H2O and KOH is recommended for obtaining a minimum carbon contamination. A low amount of oxygen is found after a prolonged dip in HF. Furthermore, the efficiency of a passivation layer for the protection of the semiconductors GaAs and GaAlAs against the influences of the atmosphere is investigated. At elevated temperatures oxygen diffuses through the passivation layer and oxidizes the semiconductor. Intermediate layers consisting of Ga2O3 or, respectively Al2O3 and As are formed. These layers can only be avoided by employing a reductive (H2) or an inert (Ar) atmosphere.相似文献