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71.
Tirapazamine (1) is a promising antitumor agent that selectively causes DNA damage in hypoxic tumor cells, following one-electron bioreductive activation. Surprisingly, after more than 10 years of study, the products arising from bioreductive metabolism of tirapazamine have not been completely characterized. The two previously characterized metabolites are 3-amino-1,2,4-benzotriazine 1-oxide (3) and 3-amino-1,2,4-benzotriazine (5). In this work, 3-amino-1,2,4-benzotriazine 4-oxide (4) is identified for the first time as a product resulting from one-electron activation of the antitumor agent tirapazamine by the enzymes xanthine/xanthine oxidase and NADPH:cytochrome P450 oxidoreductase. As part of this work, the novel N-oxide (4) was unambiguously synthesized and characterized using NMR spectroscopy, UV-vis spectroscopy, LC/MS, and X-ray crystallography. Under conditions where the parent drug tirapazamine is enzymatically activated, the metabolite 4 is produced but readily undergoes further reduction to the benzotriazine (5). Thus, under circumstances where extensive reductive metabolism occurs, the yield of the 4-oxide (4) decreases. In contrast, the isomeric two-electron reduction product 3-amino-1,2,4-benzotriazine 1-oxide (3) does not readily undergo enzymatic reduction and, therefore, is found as a major bioreductive metabolite under all conditions. Finally, the ability of the 4-oxide metabolite (4) to participate in tirapazamine-mediated DNA damage is considered. 相似文献
72.
O. Gates L. Silverman P. G. Wercholanzew I. P. Alimarin und R. E. Aresst-Jakubowitsch 《Fresenius' Journal of Analytical Chemistry》1941,121(3-4):136-137
Ohne Zusammenfassung 相似文献
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74.
Single‐Site Zeolite‐Anchored Organoiridium Carbonyl Complexes: Characterization of Structure and Reactivity by Spectroscopy and Computational Chemistry 下载免费PDF全文
Claudia Martinez‐Macias Dr. Mingyang Chen Prof. David A. Dixon Prof. Bruce C. Gates 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11825-11835
A family of HY zeolite‐supported cationic organoiridium carbonyl complexes was formed by reaction of Ir(CO)2(acac) (acac=acetylacetonate) to form supported Ir(CO)2 complexes, which were treated at 298 K and 1 atm with flowing gas‐phase reactants, including C2H4, H2, 12CO, 13CO, and D2O. Mass spectrometry was used to identify effluent gases, and infrared and X‐ray absorption spectroscopies were used to characterize the supported species, with the results bolstered by DFT calculations. Because the support is crystalline and presents a nearly uniform array of bonding sites for the iridium species, these were characterized by a high degree of uniformity, which allowed a precise determination of the species involved in the replacement, for example, of one CO ligand of each Ir(CO)2 complex with ethylene. The supported species include the following: Ir(CO)2, Ir(CO)(C2H4)2, Ir(CO)(C2H4), Ir(CO)(C2H5), and (tentatively) Ir(CO)(H). The data determine a reaction network involving all of these species. 相似文献
75.
Inside Cover: Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies (Chem. Eur. J. 14/2015) 下载免费PDF全文
76.
D. J. Gates 《Journal of statistical physics》1988,52(1-2):245-257
A Markov rate process whose transitions are captures and escapes of single atoms from the edge of a two-dimensional crystal is introduced. The stochastic equilibrium states of this process describe steady crystal growth, crystal-fluid equilibrium, and steady crystal decrescence. Exact and asymptotic growth rates are found. This extends recent results which dealt only with capture events. One application is to the growth of lamellar crystals from polymers. 相似文献
77.
We construct all on-shell, massless, supersymmetric multiplets with maximum field spin three-halves. The supergeometry of these theories is developed. We study the off-shell N = 1 matter gravitino multiplet and exhibit the supergeometries of the known theories. Explicit superfield constructions for two new off-shell theories are presented. 相似文献
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Multiple reaction pathways are available to a polyatomic molecule interacting with a solid surface. Delineation of exact temperature regions in which the various pathways are either active or inactive is accomplished using a new method, Scanning Kinetic Spectroscopy (SKS). SKS uses a calibrated and collimated beam of reactant molecules incident upon a clean single crystal surface in UHV. A multiplexed quadrupole mass spectrometer (QMS) is enclosed inside a differentially pumped random flux shield, in line of sight to the crystal surface. The crystal temperature is programmed with a linear ramp (dT/dt = 2K/s.) and reactant consumption, product evolution, and desorption of stable surface species are simultaneously measured in one experiment. SKS data are presented here which characterize the reactions of methanol with the single crystal surfaces Ni(111), Cu(111), and Cu(111) plus preadsorbed oxygen. Application of the SKS method as an efficient probe of surface reaction pathways is illustrated by the contrasting chemistry of these surfaces. The methanol plus Ni(111) system is examined in detail in order to relate the observed SKS features to specific molecular reaction pathways on the Ni(111) surface. 相似文献
80.