| 1. |
- Chen, Wenhua, et al.
(författare)
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Reduction of NO by C4 hydrocarbons on platinum in the presence of oxygen : influence of sulfur dioxide
- 1997
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 172:1, s. 3-12
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of NO, in the presence of i-C4H10or i-C4H8and O2, catalyzed by a platinum foil, was studied in order to understand better the catalytic activity of platinum metal, free of any support or dispersion effects. The reaction products were analyzed by mass spectrometry, and the surface was characterized by X-ray photoelectron spectroscopy at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates is demonstrated. The role of oxygen is interpreted as twofold: formation of active intermediates and deactivation of the surface. The effect of traces of sulfur dioxide in the reacting phase on the reduction of NO by isobutene was investigated. The influence of SO2is very much dependent upon its initial concentration in the gas phase. Low concentrations (<15 ppm) promote the reduction of NO, whereas higher levels poison the reaction by a surface site blocking effect.
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| 2. |
- Leroy, Marie-Josephe, et al.
(författare)
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Characterization of two recombinant PDE3 (cGMP-inhibited cyclic nucleotide phosphodiesterase) isoforms, RcGIP1 and HcGIP2, expressed in NIH 3006 murine fibroblasts and Sf9 insect cells
- 1996
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 35:31, s. 10194-10202
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Tidskriftsartikel (refereegranskat)abstract
- cDNAs encoding PDE3 [cGMP-inhibited cyclic nucleotide phosphodiesterase (cGI PDE)] isoforms, cGIP1 and cGIP2, have been cloned from rat (R) and human (H) cDNA libraries. The deduced amino acid sequences of RcGIP1 and HcGIP2 are very similar in their conserved catalytic domains but differ in their N-terminal regulatory domains [Meacci, E., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 3721-3725; Taira, M., et al. (1993) J. Biol. Chem. 268, 18573-18579]. cDNAs encoding both rat adipocyte RcGIP1 and human myocardial HcGIP2 (full-length forms and truncated forms lacking much of the putative N-terminal domain) were expressed in NIH 3006 fibroblasts and in Sf9 insect cells. The recombinant proteins exhibited the expected subunit molecular mass, immunologic reactivities, and characteristics of native membrane-associated forms of the enzymes, e.g., high affinity for cAMP (Km), sensitivity to the selective cGI PDE inhibitors OPC 3689 and OPC 3911 and to cGMP. The full-length recombinants were predominantly particulate, whereas the truncated HcGIP2 forms were cytosolic suggesting that N-terminal domains contain structural determinants important for membrane association. Both fibroblast RcGIP1 and authentic adipocyte cGI PDE were phosphorylated in vitro by cAMP-dependent protein kinase; tryptic [32P]peptides released from rat adipocyte 32P-cGI PDE and 32P-RcGIP1 exhibited identical electrophoretic profiles suggesting that the same peptides are phosphorylated in both.
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| 3. |
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| 4. |
- Zhao, Cheng Hua, et al.
(författare)
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Substrate specificity of acetyltransferase and reductase enzyme systems used in pheromone biosynthesis by Asian corn borer, Ostrinia furnacalis
- 1995
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Ingår i: Journal of Chemical Ecology. - 0098-0331. ; 21:10, s. 1495-1510
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Tidskriftsartikel (refereegranskat)abstract
- The substrate specificity of the acetyltransferase and the reductase enzyme systems used by Ostrinia furnacalis (Lepidoptera: Pyralidae) in pheromone biosynthesis was studied in vivo by topical application of precursors to pheromone glands. Each of the tetradecenols, varying in double bond position (from 7 to 13) and geometry of the double bond, was converted to the corresponding acetate by the acetyltransferase. The similarity in the conversion rates of all tested fatty alcohols indicated that the acetyltransferase has a low substrate specificity. Most of the corresponding tetradecenoic acids could also be converted to the respective acetates. However, very different conversion rates among the tested fatty acids demonstrated that the reductase system has a higher substrate specificity than the acetyltransferase. The conversion rates of most E isomers were higher than those of the corresponding Z isomers, except for the (Δ)-11-tetradecenoic acids, in which much more Z isomer was converted to the product. Saturated tetradecanoic acid was converted to the corresponding acetate at a high rate; the shorter homolog, tridecanoic acid, was converted at a lower rate (56%), and conversion to the respective acetates of the longer homolog, pentadecanoic and hexadecanoic acids, was insignificant (<5%). The results from the present study showed that specificity of pheromone production is to a large extent controlled by the pheromone gland reductase system.
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