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11.
Cytochrome and alternative pathway respiration in green algae : measurements using inhibitors and o(2) discrimination
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Inhibitor titration curves and discrimination against 18O2 by mitochondrial respiration in three strains of green algae (Selenastrum minutum [Naeg.] Collins, and two strains of Chlamydomonas reinhardtii Dangeard) with differing respiratory capabilities were determined. Discrimination for cytochrome pathway respiration ranged from 19.89 to 20.43%. Discrimination for alternative pathway respiration by wild-type C. reinhardtii (measured in the presence of KCN) was 25.46%, while discrimination values for a cytochrome oxidase deficient mutant of C. reinhardtii ranged from 24.24 to 24.96%. In the absence of KCN, the alternative pathway was not engaged in wild-type C. reinhardtii, the only algal strain that possessed both cytochrome and alternative pathway capacities. 相似文献
12.
High residual arylsulfatase A (ARSA) activity in a patient with late-infantile metachromatic leukodystrophy. 总被引:1,自引:0,他引:1
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J Kreysing W Bohne C Bsenberg S Marchesini J C Turpin N Baumann K von Figura V Gieselmann 《American journal of human genetics》1993,53(2):339-346
We identified a patient suffering from late-infantile metachromatic leukodystrophy (MLD) who has a residual arylsulfatase A (ARSA) activity of about 10%. Fibroblasts of the patient show significant sulfatide degradation activity exceeding that of adult MLD patients. Analysis of the ARSA gene in this patient revealed heterozygosity for two new mutant alleles: in one allele, deletion of C 447 in exon 2 leads to a frameshift and to a premature stop codon at amino acid position 105; in the second allele, a G-->A transition in exon 5 causes a Gly309-->Ser substitution. Transient expression of the mutant Ser309-ARSA resulted in only 13% enzyme activity of that observed in cells expressing normal ARSA. The mutant ARSA is correctly targeted to the lysosomes but is unstable. These findings are in contrast to previous results showing that the late-infantile type of MLD is always associated with the complete absence of ARSA activity. The expression of the mutant ARSA protein may be influenced by particular features of oligodendrocytes, such that the level of mutant enzyme is lower in these cells than in others. 相似文献
13.
In Vivo Nitrogenase Regulation by Ammonium and Methylamine and the Effect of MSX on Ammonium Transport in Anabaena flos-aquae 总被引:2,自引:2,他引:0
Ammonium suppresses nitrogenase activity in Anabaena flos-aquae (Lyng) Breb. at all pH values tested. l-Methionine-dl-sulfoximine at 1 millimolar totally inhibited glutamine synthetase, and 10 micromolar partially inhibited. Both concentrations protected nitrogenase activity from ammonium-induced suppression at pH 7.1 and 8.1. At pH 9.3 and 10.2, methionine sulfoximine did not alleviate the suppression of nitrogenase by ammonium. This pH-dependent protection of nitrogenase activity is a result of the noncompetitive inhibition of the ammonium transporter by methionine sulfoximine. At pH 7.1 and 8.2, ammonium is protonated and methionine sulfoximine inhibits its entry into the cell. At pH 9.3 and 10.2, unprotonated ammonia is abundant and may enter the cell independent of the transport system. The effects of ammonium are closely mimicked by the ammonium analog methylamine. These results suggest that ammonium per se is an important in vivo regulator of nitrogen fixation and its function can be mimicked by methylamine. Previous studies employing methionine sulfoximine may have to be re-evaluated in light of the inhibitory effects of methionine sulfoximine on the ammonium transporter. 相似文献
14.
An ammonia limited chemostat culture of Gymnodinium simplex (Lohm.) Kofoid & Swezy was perturbed with ammonia and fluctuations in the free intracellular amino acid pools were followed 80 min. The steady-state value of glutamate was 2.07 ± 10-15 mol cell-1 and of glutamine was 0.31 ± 10-15 mol cell-1. Five minutes after the perturbation, a substantial rise in glutamine was observed with a corresponding decrease in glutamate. This is considered a result of glutamine synthetase acting as the primary ammonia assimilating enzyme. The level of ammonia and the major free amino acids reached a maximum 10 min after the perturbation and then slowly decreased. 相似文献
15.
Evidence for Activation of the Oxidative Pentose Phosphate Pathway during Photosynthetic Assimilation of NO(3) but Not NH(4) by a Green Alga
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Addition of NO3− to N-limited Selenastrum minutum during photosynthesis resulted in an immediate drop in the NADPH/NADP ratio and a slower increase of the NADH/NAD ratio. These changes were accompanied by a rapid decrease in glucose-6-phosphate and increase in 6-phosphogluconate, indicating activation of glucose-6-phosphate dehydrogenase and a role for the oxidation pentose phosphate pathway during photosynthetic NO3− assimilation. In contrast, the short-term changes in pyridine nucleotides and metabolites during photosynthetic assimilation of NH4+ were not consistent with a stimulation of the oxidative pentose phosphate pathway. 相似文献
16.
Raman spectra of AMP, UTP, GMP, and CMP, and of their bromo-derivatives (8 Br-ATP, 8-bromo-adenosine, 8-bromo-guanosine, 5-bromo-deoxyuridine, 5-bromo-cytidine), are reported. They are obtained using excitation wavelengths of 457.9 nm (ionized continuous argon laser) and of 300 nm (tunable pulsed dye laser). Comparison of spectra leads to the following observations: (1) preresonances Raman effects on nucleotides spectra at 300 nm; (2) resonance Raman effects on bromoderivatives spectra at 300 nm; (3) in dilute solution (10?4M), shifts and enhancements of Raman lines of the bromo-derivatives with respect to the corresponding lines of nucleoctides. On the basis of these comparisons, the assignments of the Raman lines are discussed, This provide the necessary background for the understanding of the properties of selected groups in DNA in dilute solution. The new experimental set-up for measurements of Raman spectra using excitation in the uv regions is described. It is specially designed to incorporate the pulsed feature of the excitation laser and for correcting of the instabilities of the sourse. 相似文献
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18.
Adriana Vergs Alexandra H. Campbell Georgina Wood Lana Kajlich Aaron M. Eger Derrick Cruz Madelaine Langley Damon Bolton Melinda A. Coleman Jennifer Turpin Michaelie Crawford Nigel Coombes Adam Camilleri Peter D. Steinberg Ezequiel M. Marzinelli 《Ecological Management & Restoration》2020,21(2):74-85
Operation Crayweed focuses on the restoration of underwater forests that disappeared from the coastline of Sydney, Australia’s largest city, 40 years previously. We show how a combination of science, hands‐on restoration, community engagement and art has helped the project to reach its goals as well as raise awareness about the importance of underwater kelp forests that are experiencing global decline. 相似文献
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OLIVIER PIERRE GILBERT ENGLER JULIE HOPKINS FRÉDÉRIC BRAU ERIC BONCOMPAGNI DIDIER HÉROUART 《Plant, cell & environment》2013,36(11):2059-2070
Legumes form a symbiotic interaction with Rhizobiaceae bacteria, which differentiate into nitrogen‐fixing bacteroids within nodules. Here, we investigated in vivo the pH of the peribacteroid space (PBS) surrounding the bacteroid and pH variation throughout symbiosis. In vivo confocal microscopy investigations, using acidotropic probes, demonstrated the acidic state of the PBS. In planta analysis of nodule senescence induced by distinct biological processes drastically increased PBS pH in the N2‐fixing zone (zone III). Therefore, the PBS acidification observed in mature bacteroids can be considered as a marker of bacteroid N2 fixation. Using a pH‐sensitive ratiometric probe, PBS pH was measured in vivo during the whole symbiotic process. We showed a progressive acidification of the PBS from the bacteroid release up to the onset of N2 fixation. Genetic and pharmacological approaches were conducted and led to disruption of the PBS acidification. Altogether, our findings shed light on the role of PBS pH of mature bacteroids in nodule functioning, providing new tools to monitor in vivo bacteroid physiology. 相似文献