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The isozymic nature and kinetic properties of glutamate dehydrogenase from safflower seedlings 总被引:1,自引:0,他引:1
Levels of glutamate dehydrogenase (GDH) [L-glutamate: NAD oxidoreductase(deaminating), EC 1.4.1.2
[EC]
] from safflower roots and cotyledonsincreased (?2.7) and decreased ( ?5.7), respectively, as a functionof seedling age. No significant changes in enzyme levels weredetected during hypocotyl development. GDH preparations of thedifferent organs were resolved by polyacrylamide gel electrophoresisinto 2 to 4 isozymes. The isozymic pattern was influenced byseedling age and organ tested. The slowest moving isozyme (No.1) appears to be responsible for the changes in GDH levels observedin cotyledons and roots. We isolated isozyme 1 and GDH fractionchiefly containingisozyme 2, by DEAE-cellulose chromatography. GDH was purified approximately 53-fold from the particulatefraction of cotyledons. The pH optima for NADH and NAD activitieswere 8.2 and 8.9, respectively. Michaelis constants were foundto be: -ketoglutarate, 8mM; glutamate, 4 mM; ammonium, 35.4mM; NAD, 0.26 mM; NADH, 0.065 mM. Km values of isozymes 1 and2 were similar. The binding order of substrates in die reductiveamination reaction was NADH, -ketoglutarate and NH4+. (Received July 17, 1972; ) 相似文献
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Kristen M. Reifel Brandon K. Swan Errel Olivo James M. Watts Charles C. Trees Stuart H. Hurlbert 《Hydrobiologia》2007,576(1):167-183
The influence of river inflows (2.5–5 g l−1) on phytoplankton and zooplankton was assessed with samples collected at 17 sites around the 50 km perimeter of the southern
basin of the Salton Sea (41–45 g l−1) along the 5 m isobath on 2 September and 11 December 2000. Phytoplankton generally increased in abundance downcurrent of
the points of inflow, but patterns in downcurrent abundance varied widely among species. Several diatom species showed large
increases; Chaetoceros muelleri var subsalsum, Cylindrotheca closterium and Thalassionema sp. increased up to 800-fold in abundance by ca. 20 km downcurrent from inflow points in September. In contrast, the dinoflagellates
Gyrodinium uncatenum and Prorocentrum minimum increased 6- and 4-fold, respectively, in December, and Gonyaulax grindleyi actually decreased downcurrent of the rivers in September. In September, patterns in downcurrent abundance were correlated
with the ratio of cell surface area to cell biovolume, with species with high ratios showing the largest increases. Zooplankton
abundances did not show regular trends downcurrent of river inflows except for the larvae of Balanus amphitrite, which increased in density ca. 100-fold. This increase most likely reflected the abundance of adult-colonized rocky substrates
near river inflow points. The strong upcurrent trends documented for some species seemed to have been due to the injection
of nutrient-rich water from central to nearshore areas and near-site mortality due to the presence of hydrogen sulfide. This
study gives a first glimpse of the complexity of the responses of nearshore plankton to river inflow and provides evidence
for how changes in factors such as current speed, nutrient supply and salinity stratification may influence plankton dynamics.
Guest Editor: John M. Melack
Saline Waters and their Biota 相似文献
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