1. We evaluated the specificity of 15 substrates and 14 inhibitors of the cytochrome P450s using nine human P450 forms expressed in HepG2 cells using a recombinant vaccinia virus and also in human liver microsomes. 2. Coumarin, 7-ethoxyresorufin, 7-benzyloxyresorufin, tolbutamide, aniline and diazepam were form-selective substrates towards CYP2A6, the CYP1A subfamily, CYP2B6, the CYP2C subfamily, CYP2E1 and the CYP3A subfamily respectively. However, a selective substrate for CYP2D6 was not found among the chemicals tested. 3. SKF-525A inhibited > 40% of the metabolic activity of all substrates tested, and the inhibitory effects differed among P450 forms. Sulphaphenazole, 7,8-benzoflavone, quinidine and troleandomycin were selective inhibitors of the CYP2C subfamily (except CYP2C19), the CYP1A subfamily, CYP2D6 and the CYP3A subfamily respectively. Methoxsalen (CYP2A6 inhibitor) inhibited the metabolic activity of CYP1A2 as well as that of CYP2A6. Diethyldithiocarbamate (CYP2E1 inhibitor) inhibited the metabolic activities of CYP2A6 and CYP2C19 in addition to that of CYP2E1. 4. Our results indicated that substrates and inhibitors reported as P450 selective probes are not necessarily specific for individual human P450 forms. These results may provide useful information regarding human P450 substrates and inhibitors in vitro using human liver microsomal samples.
Reactions of oxaziridines 1 with a ketene, isocyanates, and a carbodiimide are studied, and the results are quite different from those of oxiranes, aziridines, or thiiranes. With diphenylketene (2), 2-n-alkylor sec-alkyloxaziridines give 3-alkyl-5,5-diphenyl-2-diphenylmethylidene-l,3-oxazolidin-4-ones (3), but 2-tert-butyloxaziridine If rearranges to N-tert-butylbenzamide. In the reactions with isocyanates, cycloadditions forming 1,2,4oxadiazolidin-5-ones 10 are exclusively observed. The reactions similar to that with the ketene 2 occur between 2-n-alkyloxaziridines and diphenylcarbodiimide, giving hexahydro-l,3,5-triazine derivatives 17 as a result of hydride shift. The oxaziridine If undergoes 1:1 cycloaddition with the carbodiimide.
The rate of the ferrous oxidation at 150°C is 6.10×10−4sec−1 for sulfate, and 2.78×10−4sec−1 for chloride at the oxygen pressure of 30 atm. The precipitation reaction of iron species is through hydrolyzed ferric ions even in the ferrous solution. The rate of precipitation for ferric sulfate is given in Fig. 7, with the activation energy of 12.5 kcal./mol. The precipitate is amorphous at 100°C and completely α-Fe2O3 at 200°C.
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