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Chandra Sekhar Gahan Jan‐Eric Sundkvist Mark Dopson Åke Sandström 《Biotechnology and bioengineering》2010,106(3):422-431
Biomining is the use of microorganisms to catalyze metal extraction from sulfide ores. However, the available water in some biomining environments has high chloride concentrations and therefore, chloride toxicity to ferrous oxidizing microorganisms has been investigated. Batch biooxidation of Fe2+ by a Leptospirillum ferriphilum‐dominated culture was completely inhibited by 12 g L?1 chloride. In addition, the effects of chloride on oxidation kinetics in a Fe2+ limited chemostat were studied. Results from the chemostat modeling suggest that the chloride toxicity was attributed to affects on the Fe2+ oxidation system, pH homeostasis, and lowering of the proton motive force. Modeling showed a decrease in the maximum specific growth rate (µmax) and an increase in the substrate constant (Ks) with increasing chloride concentrations, indicating an effect on the Fe2+ oxidation system. The model proposes a lowered maintenance activity when the media was fed with 2–3 g L?1 chloride with a concomitant drastic decrease in the true yield (Ytrue). This model helps to understand the influence of chloride on Fe2+ biooxidation kinetics. Biotechnol. Bioeng. 2010; 106: 422–431. © 2010 Wiley Periodicals, Inc. 相似文献
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Ely F Pedroso MM Gahan LR Ollis DL Guddat LW Schenk G 《Journal of inorganic biochemistry》2012,106(1):19-22
OpdA is a binuclear metalloenzyme that can hydrolyze organophosphate pesticides and nerve agents. In this study the crystal structure of the complex between OpdA and phosphate has been determined to 2.20 Å resolution. The structure shows the phosphate bound in a tripodal mode to the metal ions whereby two of the oxygen atoms of PO4 are terminally bound to each metal ion and a third oxygen bridges the two metal ions, thus displacing the μOH in the active site. In silico modelling demonstrates that the phosphate moiety of a reaction product, e.g. diethyl phosphate, may bind in the same orientation, positioning the diethyl groups neatly into the substrate binding pocket close to the metal center. Thus, similar to the binuclear metallohydrolases urease and purple acid phosphatase the tripodal arrangement of PO4 is interpreted in terms of a role of the μOH as a reaction nucleophile. 相似文献
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Two cytochemical methods for the localization of acid and alkaline invertases are given. The first is based upon the reduction of a silver complex at two different pH ranges, whilst the second is based upon the tetrazolium reaction and permits quantification of the rate of activity of alkaline invertase activity. The distribution of alkaline invertase activity throughout the root apex of Pisum sativum and the cell wall localization of acid invertase for material excised from tuber tissue of Helianthus tuberosus are both confirmed. 相似文献
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The chromatin extracted from rat hepatocytes of different ages has been shown to contain a phospholipid fraction representing 0.47-0.59 per cent of total chromatin in newborn animals and 0.22 per cent in 45-day-old animals. No such age-related differences are observed in the nuclei. The phospholipid composition of the nuclei at different ages shows a higher level of sphingomyelin and a lower level of phosphatidylserine in newborn than in adult animals. Chromatin phospholipids have a completely different composition from that of nuclei with respect to age, particularly in newborn rats, where there is a decrease in phosphatidylcholine and an increase in phosphatidylserine. 相似文献
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