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《Geobios》1999,32(3):482
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Measurements of the 1H NMR spectra of the diastereoisomers of 1-(tetrahydro-2-furanyl)-5-fluorouracil, 3-(tetrahydro-2-furanyl)-5-fluorouracil, and 1,3-bis(tetrahydro-2-furanyl)-5-fluorouracil in the presence of tris[3-(2,2,2-trifluoro-1-hydroxyethylidene)-d-camphorato]europium(Eu(TFC)3) as a chiral shift reagent showed differences between the isomers in the chemical shift changes of the protons of C2'-H and C6-H etc.  相似文献   

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Several rate constants for one-electron reduction of cytochrome P450 are more rapid in the absence than in the presence of the specific substrate. The respective values for methyl viologen, nicotinamide adenine dinucleotide and the 1-methyl-4-(and -3-)carbamidopyridinium radicals are 2.6, 3.4, 6 and 35 × 107 M?1 s?1 without camphor, and 0.15, 0.1, 1.8 and 110 × 107 M?1 s?1 for the camphor complex. Hydrated electrons react with cytochrome P450 with a rate constant of 3.0 × 1010 M?1 s?1 whether camphor is bound or not, but little of the reduction takes place at the haem iron. No reduction of the haem iron by CO2?- or O2?- could be detected, whether camphor is bound or not.  相似文献   

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A crude preparation of 2-phenyladenosine was found to be mutagenic in the Ames Salmonella assay. In the purification of this preparation, it was revealed that 2-phenyladenosine itself was nonmutagenic but that 2-(m- and p-nitrophenyl)-adenosines (5m,p) contaminating the sample were the mutagenic principles. A structure-activity relationship study was carried out, and it was found that 5p, 2-(p-nitrophenyl)-adenine (7p), and 2-(p-nitrophenyl)-2'-deoxyadenosine (15p) were strongly mutagenic toward S. typhimurium TA98 and TA100 without metabolic activation, the potency being in the order 15p greater than 7p greater than 5p. The potency of 15p in TA98 was one order of magnitude greater than that of 4-nitroquinoline N-oxide. 15p also showed mutagenicity in the mouse cell line FM3A in culture.  相似文献   

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The 2- and 8-azido trimer 5'-triphosphate photoprobes of 2-5A have been enzymatically synthesized from [gamma-32P]2-azidoATP and [alpha-32P]8-azidoATP by 2-5A synthetase from rabbit reticulocyte lysates. Identification and structural determination of the 2- and 8-azido adenylate trimer 5'-triphosphates were accomplished by enzymatic hydrolyses with T2 RNase, snake venom phosphodiesterase, and bacterial alkaline phosphatase. Hydrolysis products were identified by HPLC and PEI-cellulose TLC analyses. The 8-azido photoprobe of 2-5A displaces p3A4[32P]pCp from RNase L with affinity equivalent to p3A3 (IC50 = 2 X 10(-9) M in radiobinding assays). The 8-azido photoprobe also activates RNase L to hydrolyze poly(U) [32P]pCp 50% at 7 X 10(-9) M in core-cellulose assays. The 2- and 8-azido photoprobes and authentic p3A3 activate RNase L to cleave 28S and 18S rRNA to specific cleavage products at 10(-9) M in rRNA cleavage assays. The nucleotide binding site(s) of RNase L and/or other 2-5A binding proteins in extracts of interferon-treated L929 cells were investigated by photoaffinity labeling. Dramatically different photolabeling patterns were observed with the 2- and 8-azido photoprobes. The [gamma-32P]2-azido adenylate trimer 5'-triphosphate photolabels only one polypeptide with a molecular weight of 185,000 as determined by SDS gel electrophoresis, whereas the [alpha-32P]8-azido adenylate trimer 5'-triphosphate covalently photolabels six polypeptides with molecular weights of 46,000, 63,000, 80,000, 89,000, 109,000, and 158,000. Evidence that the photolabeling by 2- and 8-azido 2-5A photoprobes was highly specific for the p3A3 allosteric binding site was obtained as follows.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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《Carbohydrate research》1986,147(2):247-264
l-(1-13C, 5-2H)Arabinose (6D) and l-(2-13C, 5-2H)arabinose (8D) have been synthesized by degradation of 2,3-O-isopropylidene-α-l-rhamnofuranose (2) to l-(4-2H)erythrose (,D), with subsequent chain elongation to 6D plus l-(1-13C, 5-2H)ribose (7D), the latter being converted into 8D. Intermediates were identified by complete assignment of the 13C chemical shifts employing carbon-carbon and carbon-deuterium coupling constants, deuteration shifts, differential isotope-shifts, and deuterium spectra. The anomeric carbon atoms of 2 and 2,3-O-isopropylidene-l-(1-2H) erythrose (4D) gave only single 13C resonances, suggesting that these two compounds exists in only one major anomeric configuration, clarifying previously reported work. The synthesis of 2,3-O-isopropylidene-l-(1-2H)rhmanitol (3D) facilitated the assignment of the signals in the 13C spectra of the nondeuterated analog. Specific deuterium-enrichment and the observed carbon-deuterium coupling (1JC,D ∼22 Hz) not only served to identify the deuterated carbon atom unambiguously in 3 but also permitted assignment of closely spaced resonances. The deuterium spectrum of 2,3-O-isopropylidene-l-(1-2H)erythrofuranose (4D) showed only a single resonance, indicating preponderance of one anomer, in accord with the observation of a single C-1 resonance in the 13C spectrum.  相似文献   

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The two hydrazone-compounds 2-(phenylethylhydrazono)-propionic acid (PEHP) and 2-(2-cyclohexyl-ethylhydrazono)-propionic acid (CHEHP) significantly lowered the blood glucose level in several laboratory animals fasted 48 hours (guinea pigs, mice, hamsters and rats). In the guinea pig, PEHP produced a three times stronger hypoglycemic effect than phenelzine, its corresponding hydrazine. Conversely both hydrazono compounds decreased the monoamine oxidase activity much less, than phenelzine. CHEHP (145 mumol/kg) inhibited this enzyme by less than 14%. After oral administration both hydrazones (200 mumol/kg) also produced a distinct hypoglycemic effect. The blood glucose lowering properties of the two hydrazones were most manifest in fasted guinea pigs, diabetic mice and rats with streptozotozin diabetes.  相似文献   

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