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排序方式: 共有147条查询结果,搜索用时 15 毫秒
1.
2.
When a new strain of Pseudomonas aeruginosa was grown aerobically and then transferred to anaerobic conditions, cells reduced NO
3
–
quantitatively to NO
2
–
in NO
3
–
-respiration. In the absence of nitrate, NO
2
–
was immediately reduced to NO or N2O but not to N2 indicating that NO
2
–
-reductase but not N2O-reductase was active. The formation of the products NO or N2O depended on the pH in the medium and the concentration of NO
2
–
present. When P. aeruginosa was grown anaerobically for at least three davs N2O-reductase was also active. Such cells reduced NO to N2 via N2O. The new strain generated a H+-gradient and grew by reducing N2O to N2 but not by converting NO to N2O. For comparison, Azospirillum brasilense Sp7 showed the same pattern of NO-reduction. In contrast, Paracoccus denitrificans formed 3.5 H+/NO during the reduction of NO to N2O in oxidant pulse experiments but could not grow in the presence of NO. Thus the NO-reduction pattern in P. denitrificans on one side and P. aeruginosa and A. brasilense on the other was very different. The mechanistic implications of such differences are discussed. 相似文献
3.
A sodium dodecyl sulfate-gradient gel electrophoresis system that separates polypeptides in the molecular weight range of 1500 to 100,000 总被引:1,自引:0,他引:1
A sodium dodecyl sulfate-polyacrylamide gradient gel system is described. It combines a linear gradient in polyacrylamide from 10.2 to 30.2% in the separating gel and the discontinuous ammediol/glycine buffer system suggested by Bury (A. F. Bury, 1981, J. Chromatogr. 213, 491-500). This urea-free electrophoretic system provides high resolution and clean separation patterns of proteins and polypeptides with molecular weights from 1500 to 100,000. It is especially suited for studying complex mixtures of proteins and proteolytic fragments, in particular with regard to immunoelectrotransfer blot techniques. 相似文献
4.
The stoicheiometry of electron transfer by bacterial and plant ferredoxins 总被引:5,自引:1,他引:4 下载免费PDF全文
1. The number of electrons carried by ferredoxins from spinach, the blue-green alga Anacystis nidulans, the anaerobic bacterium Clostridium welchii and the photosynthetic bacterium Chromatium was determined. 2. Ferredoxins were reduced by illuminated chloroplasts, and the stoicheiometry of the reoxidation in the dark of the ferredoxins by NADP and benzyl viologen was measured. 3. Spinach and A. nidulans ferredoxins were found to be one-electron carriers, and Cl. welchii and Chromatium ferredoxins were two-electron carriers. 相似文献
5.
Cyanelles from Cyanophora paradoxa can easily be isolated and assayed for their carrier composition by the silicone oil filtering technique. The present investigation demonstrates a Pi-translocator transferring phosphate, dihydroxyacetone phosphate and 3-phosphoglycerate in a counter exchange mode in cyanelles as in chloroplasts of higher plants. The uptake of Pi is inhibited by dihydroxyacetone phosphate, phosphoglycerate and glucose-6-P, only poorly by phosphoenolpyruvate and not by 2-phosphoglycerate. The inhibitors pyridoxalphosphate and 4,4′diisothiocyanostilbene-2,2K'disulfonic acid at low concentration also affect Pi-uptake. Cyanelles probably transport photosynthate (reductant and ATP) by triosephosphates. This is the first demonstration of a phosphate translocator in an organism of a low evolutionary scale. Cyanelles also transport glucose which proceeds in two phases. In the lower concentration range (≤ 2.5 mM), glucose penetrates by facilitated diffusion, whereas transport follows first-order kinetics at higher amounts (> 2.5 mM). In the low concentration range, glucose-transport is affected by high concentrations of 3-O-methylglucose and fructose. The physiological role of the glucose-transport carrier in Cyanophora is doubtful. It may function in transporting glucose into cyanelles if the carbon level inside them becomes limiting, e.g. in dark periods. 相似文献
6.
Abstract The present communication defines the conditions under which thioredoxin activates glutamine synthetase from Anabaena cylindrica . Effects are obtained at pH values around neutrality, and the activation is affected by Mg2+ in the assays. The thioredoxin systems from A. cylindrica and spinach are functionally interchangeable in the activation of glutamine synthetase. The enzyme is efficiently activated by thioredoxinm and also by thioredoxinf , but at much higher concentrations. Thioredoxinm has previously been shown to activate NADPH-dependent malate dehydrogenase and isocitrate dehydrogenase from cyanobacteria. It is speculated that thioredoxinm plays a role in the differentiation of vegetative cells to heterocysts. 相似文献
7.
The blue-green alga Anabaena cylindrica is found to consume molecular hydrogen in a hydrogenase dependent reaction. This hydrogen uptake proceeds in the dark and is strictly dependent on oxygen, thus representing a Knallgas reactions. Its rate is almost as high as that of the endogenous respiration in Anabaena. Studies with inhibitors reveal that hydrogen is utilized via the complete respiratory chain providing additional energy for the alga. CO plus C2H2 completely block the Knallgas reaction which explains the previously reported considerable increase in the total H2 formation representing the difference between the nitrogenase-dependent H2-evolution and the reutilization of the gas catalysed by the hydrogenase in intact Anabaena.H2 is able to support the C2H2-reduction in the dark in a reaction again strictly dependent on oxygen. Moreover, H2 is also consumed in experiments carried out under far red light and in the presence of dichlorophenyl-dimenthyl-urea (DCMU) where the energy for nitrogen fixation is no longer provided by respiration but by cyclic photophosphorylation. Under these conditions, H2 is found to supply electrons for the formation of C2H4 from C2H2 in a reaction no longer dependent on the presence of oxygen. Moreover, in these experiments, the presence of H2 stabilizes the C2H2-reduction activity against the deleterious effect of oxygen.Thus, this communication provides evidence for a triplicate function of the H2-uptake catalysed by hydrogenase in intact Anabaena which is (a) to provide energy by the Knallgas reaction, (b) to supply reducing equivalents for nitrogenase, (c) to protect nitrogenase from damage by oxygen.Abbreviations DCMU
N-(3,4-dichlorophenyl)N,N-dimethylurea
- DNP
2-4-dinitrophenol
- FCCP
carbonylcyanid-p-trifluormethoxyphenyl-hydrazone(=p-CF3-CCP)
- Chl
chlorophyll 相似文献
8.
Nitrogen-fixingAnabaena cylindrica cells are found to evolve hydrogen in high quantities in the presence of CO plus C2H2. Studies with the inhibitors dichlorophenyldimethylurea (DCMU), disalicylidenepropanediamine (DSPD), dibromothymoquinone (DBMIB), undecylbenzimidazole (UDB) and chloro-carbonyl-cyanide-phenylhydrazone (CCCP) and also withAnabaena grown on nitrate- and ammonia-nitrogen show that the H2-formation is due to the ATP-dependent H3O+-reduction catalysed by nitrogenase. In control experiments CO plus C2H2 inhibited the activities of a cell-free hydrogenase fromClostridium pasteurianum. It is concluded that Anabaena has a hydrogenase whose natural function is to recycle the H2 lost by the action of nitrogenase.Abbreviations Cl-CCP
m-chloro-carbonyl-cyanide-phenylhydrazone
- DSPD
disalicylidenepropanediamine(1–3)
- DBMIB
dibromothymoquinone
- DCMU
N-(3,4-dichlorophenyl) NN-dimethyl-urea
- UDB
2-undecyl-benzimidazole 相似文献
9.
10.
Element distribution in mycorrhizal and nonmycorrhizal roots of the halophyte Aster tripolium determined by proton induced X-ray emission 总被引:2,自引:0,他引:2
Summary. The salt aster (Aster tripolium L.) colonized by the arbuscular mycorrhizal fungus Glomus intraradices Sy167 and noncolonized control plants were grown in a greenhouse for nine months with regular fertilization by Hoagland nutrient solution supplemented with 2% NaCl. Mycorrhizal roots showed a high degree of mycorrhizal colonization of 60–70% and formed approximately 25% more dry weight and much less aerenchyma than the nonmycorrhizal controls. Cryosectioning essentially preserved the root cell structures and apparently did not cause significant ion movements within the roots during cuttings. The experimental conditions, however, did not allow to discriminate between fungal and plant structures within the roots. Quantification of proton-induced X-ray emission (PIXE) data revealed that in control roots, Na+ was mainly concentrated in the outer epidermal and exodermal cells, whereas the Cl– concentration was about the same in all cells of the roots. Cross sections of roots colonized by the mycorrhizal fungus did not show this Na1 gradient in the concentration from outside to inside but contained a much higher percentage of NaCl among the elements determined than the controls. PIXE images are also presented for the four other elements K, P, S, and Ca. Both in colonized and control roots, the concentration of potassium was high, probably for maintaining homoeostasis under salt stress. This is seemingly the first attempt to localize both Na+ and Cl– in a plant tissue by a biophysical method and also demonstrates the usefulness of PIXE analysis for such kind of investigation. 相似文献