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791.
Aiguo Li Zhijun Zhang Yangjie Wu Haoyun An Reed M. Izatt Jerald S. Bradshaw 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(4):317-327
Five new bis(benzo-15-crown-5) derivatives with different connecting groups were synthesized. Potassium ion-selective PVC membrane electrodes based on these bis(crown ether)s were prepared and their selective properties were measured. The results showed that most of these electrodes are stable over a wide pH range and their selectivity coefficients were better than those of an electrode based on natural valinomycin. 相似文献
792.
Amy Avelar Fook S. Tham Christopher A. Reed Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(19):3491-3493
Acid remarks : The anhydrous diprotic boron acids H2(B12X12) (X=Cl, Br; see picture, B orange, X green) are the first examples of diprotic superacids and may be the strongest acids yet isolated. Both protons protonate benzene to give benzenium ion salts that are stable at room temperature. These acids owe their existence to the stability of the icosahedral B12 cluster with its dinegative charge buried beneath a layer of halide substituents.
793.
Yangjie Wu Haoyun An Jingchao Tao Jerald S. Bradshaw Reed M. Izatt 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(3):267-274
Complexes of nine 4'-substituted benzo-15-crown-5 ligands with sodium picrate were prepared. A good linear relationship of the . values from the UV spectra and Hammett [p - m] values was observed. Charge transfer complexes of ten 4'-substituted benzo-l5-crown-5 ligands with picric acid were isolated in crystalline form. The color of the complexes depended on the nature of the substituents. All of the complexes were identified by elemental analyses, UV and IR spectra. 相似文献
794.
Astashkin AV Seravalli J Mansoorabadi SO Reed GH Ragsdale SW 《Journal of the American Chemical Society》2006,128(12):3888-3889
Pyruvate ferredoxin oxidoreductase (PFOR) is central to the anaerobic metabolism of many bacteria and amitochondriate eukaryotes. PFOR contains thiamine pyrophosphate (TPP) and three [4Fe-4S] clusters, which link pyruvate oxidation to reduction of ferredoxin. In the PFOR reaction, TPP reacts with pyruvate to form lactyl-TPP, which undergoes decarboxylation to form a hydroxyethyl-TPP (HE-TPP) intermediate. One electron is then transferred from HE-TPP to one of the three [4Fe-4S] clusters to form an HE-TPP radical and a [4Fe-4S]1+ intermediate. Pulsed EPR methods have been used to measure the distance between the HE-TPP radical and the [4Fe-4S]1+ cluster to which it is coupled. Computational analysis including the PFOR crystal structure and the spin distribution in the HE-TPP radical and in the reduced [4Fe-4S] cluster demonstrates that the distance between the HE-TPP radical and the medial cluster B matches the experimentally determined dipolar interaction, while one of the other two clusters is too close and the other is too far away. These results clearly demonstrate that it is the medial cluster (cluster B) that is reduced. Thus, rapid electron transfer occurs through the electron-transfer chain, which leaves an oxidized proximal cluster poised to accept an electron from the HE-TPP radical in the subsequent reaction step. 相似文献
795.
Didem Sünbül Huceste atalgil‐Giz Wayne Reed Ahmet Giz 《Macromolecular theory and simulations》2004,13(2):162-168
Summary: A new error‐in‐variables method was developed to estimate the reactivity ratios in copolymerization systems. It brings the power of automatic, continuous, on‐line monitoring of polymerization (ACOMP) to copolymerization calculations. In ACOMP systems, monomer and polymer concentrations are measured by the monitoring of two independent properties of the system. The reactivity ratios are found by taking into account errors in the monomer concentrations determined from measurements and from calibration of the instruments. All the error sources are taken into account according to the error‐in‐variables method, and their effects are reflected in determining the confidence intervals of the reactivity ratios by the usual error propagation technique.
796.
The existence of sitting-atop metalloporphyrin complexes, the proposed intermediates in the metalation of free-base porphyrins, has been explored via the microscopic reverse reaction, i.e., protonation of metalloporphyrins with a strong acid. The reaction of M(Tp-TP) (M = Zn, Cu, Ni; Tp-TP = dianion of tetra-p-tolylporphyrin) with mesitylenium carborane salts produced only the demetalated porphyrin in its diprotonated form, [H4Tp-TP][carborane]2 (carborane = CHB11H5Cl6-, CHB11H5Br6-, CHB11Cl11-). In arene solvents, the H4Tp-TP2+ dication shows an unusually upfield shifted 1H NMR resonance at ca. -6 ppm, which X-ray crystallography reveals to arise from N-H- - -pi hydrogen bonding of the acidic protons to arene solvent molecules. 相似文献
797.
Rational design and real time, in-cell detection of the proapoptotic activity of a novel compound targeting Bcl-X(L) 总被引:6,自引:0,他引:6
Becattini B Kitada S Leone M Monosov E Chandler S Zhai D Kipps TJ Reed JC Pellecchia M 《Chemistry & biology》2004,11(3):389-395
Antiapoptotic Bcl-2-family proteins Bcl-2 and Bcl-X(L) have been recently validated as drug discovery targets for cancer. Here, by using a combination of molecular modeling, NMR-based structural analysis, fluorescence polarization assays, and cell-based assays, we have designed and characterized a novel proapoptotic compound targeting these proteins. Our compound, Apogossypol, is capable of binding and inhibiting Bcl-2 and Bcl-X(L) with high affinity and induces apoptosis of tumor cell lines. Mechanistic studies on the action of our compound were also performed via confocal microscopy that provided real-time detection of the interaction with Bcl-X(L) in intact cells. Finally, preliminary data on cells freshly isolated from patients affected by chronic lymphocytic leukemia strongly suggest potential applications of Bcl-2 antagonists as chemosensitizers in cancer therapy. 相似文献
798.
Mathematical Programming - Even and odd pairs are important tools in the study of perfect graphs and were instrumental in the proof of the Strong Perfect Graph Theorem. We suggest that such pairs... 相似文献
799.
B. Cameron Reed 《Annalen der Physik》2018,530(6)
Despite longstanding speculation concerning the harnessing of atomic energy, the prospect of doing so was not a foregone conclusion upon the discovery of fission in late 1938. Many aspects of the new phenomenon such as secondary neutrons, cross‐sections, and energetics had to be investigated before the feasibility of nuclear reactors or explosives could be established. Here, experimental and theoretical developments in the 18 months following the discovery of fission are summarized; these develeopments laid the groundwork for wartime nuclear programs. 相似文献
800.