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1.
A nitrite reductase was identified and purified 11 -fold from the cytoplasmic fraction of Salmonella typhimurium grown anaerobically with nitrite as the sole nitrogen source. The enzyme required NADH as a cofactor and showed maximum in vitro reductase activity at pH 8.0.
S. typhimurium, grown anaerobically in glucose-limited minimal medium containing peptone and nitrite, showed shorter generation times and increased cell yields in comparison to nitrite-free cultures. The presence of nitrite had no effect on aerobic cultures. The nitrite reductase functions in a dissimilatory manner and appears to be primarily involved in physiological energy generation during anaerobic growth. The nitrite reductase may function to remove excess reducing power in the form of NADH from the cell thus increasing ATP production during the anaerobic fermentation of glucose. The formation and subsequent assimilation of ammonia from nitrite is of secondary importance to the organism. 相似文献
S. typhimurium, grown anaerobically in glucose-limited minimal medium containing peptone and nitrite, showed shorter generation times and increased cell yields in comparison to nitrite-free cultures. The presence of nitrite had no effect on aerobic cultures. The nitrite reductase functions in a dissimilatory manner and appears to be primarily involved in physiological energy generation during anaerobic growth. The nitrite reductase may function to remove excess reducing power in the form of NADH from the cell thus increasing ATP production during the anaerobic fermentation of glucose. The formation and subsequent assimilation of ammonia from nitrite is of secondary importance to the organism. 相似文献
2.
Harvesting experiments revealed that immature whole mushrooms with closed veils had higher 1-octen-3-0l levels than more mature whole mushrooms with open veils. The l-octen-3-01 content of the gills was higher in immature mushrooms with closed veils, gradually decreased with maturity as the veil opened, and finally increased after the gills were well exposed. Postharvest experiments demonstrated that storage temperature influenced the activity of lipoxygenase-hydroperoxide lyase, but no differences in 1-octen-3-01 content were observed. Enzyme activity as well as 1-octen-3-01 content decreased during storage. Addition of calcium chloride to irrigation water, employed to improve quality and shelf life of fresh mushrooms, increased the amount of l-octen-3-01 immediately after harvest. 相似文献
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This paper develops an electrical analogue for a gearbox suitable for use in the time-domain modelling of many electromechanical systems, with tensor methods being used to define the changing conditions in the gearbox brought about by backlash. Unlike most existing models it is compatible with the time-varying and discontinuous models often used to describe the electrical items of a typical system, and it allows for the effects of these items of mechanical non-linearities and discontinuities such as friction and backlash. 相似文献
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Tillman JA Lu F Goddard LM Donaldson ZR Dwinell SC Tittiger C Hall GM Storer AJ Blomquist GJ Seybold SJ 《Journal of chemical ecology》2004,30(12):2459-2494
7.
Hydroxylation of the C-6 position of pyridoxine has been described recently as a mechanism for the degradation of vitamin B6 in foods. The nutritional properties of the resulting 6-hydroxypyridoxine in mammals have not been previously evaluated. 6-Hydroxypyridoxine was synthesized and its structure confirmed by UV and NMR spectroscopy. A rat bioassay with multiple dose levels was conducted to compare the vitamin B6 activity of pyridoxine and 6-hydroxypyridoxine with respect to a variety of indices of vitamin B6 metabolism. By all criteria employed, 6-hydroxypyridoxine exhibited neither vitamin B6 nor antivitamin B6 activity and, thus, is nutritionally inert. 相似文献
8.
The carotenoids of red bell peppers were analyzed without saponifi-cation by high performance liquid chromatography using octadecyl silica as stationary and methanol-ethyl acetate as mobile phases. The red bell peppers contained 280 ug/gm total carotenoids. Capsanthin accounted for 60% of the total carotenoids. Also present were 11%beta-carotene and 20% capsorubin. Capsanthin was acylated with C12 to C18 saturated fatty acids. 相似文献
9.
Network Access Pricing and Deregulation 总被引:3,自引:0,他引:3
The paper addresses the question of pricing access to the networkfacilities of an incumbent firm after deregulation. Networkaccess pricing continues to be regulated in such industriesas telecommunications, railroads, eletric power and naturalgas. We emphasize that access prices should be set such thatthey satisfy an individual rationality condition for the incumbentfirm so that access is granted voluntarily. We examine the effectsof the voluntary access condition incentives for entry and showthat properly chosen access prices incentives for efficiententry using several alternative competition models: BertrandNash,CournotNash and competition Chamberlin with differentiatedproducts. 相似文献
10.
Dry whole-milk powders containing 0, 30, 50 and 70% nominal lactose prepared by spray-drying alone, or followed by post-drying crystallization, were incorporated into milk chocolate to give 0–50% substitution of lactose for sucrose. Increasing the concentration of amorphous lactose from spray-dried powders in the chocolates decreased viscosity, increased particle size of refined chocolate mass, and lowered the concentration of surface-active agents at which a minimum in Casson yield value was observed. Increasing the concentration of crystalline lactose from milk powders in the chocolates increased viscosity, decreased particle size, and increased the concentration of surface-active agents at which a minimum in Casson yield value was observed. Conditions which affect lactose crystallinity in milk powders, such as improper storage and handling prior to use in chocolate production, could be responsible for variations in chocolate viscosity noted sometimes by processors. 相似文献