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Rosalie Tran Jan Kern Johan Hattne Sergey Koroidov Julia Hellmich Roberto Alonso-Mori Nicholas K. Sauter Uwe Bergmann Johannes Messinger Athina Zouni Junko Yano Vittal K. Yachandra 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2014,369(1647)
The structure of photosystem II and the catalytic intermediate states of the Mn4CaO5 cluster involved in water oxidation have been studied intensively over the past several years. An understanding of the sequential chemistry of light absorption and the mechanism of water oxidation, however, requires a new approach beyond the conventional steady-state crystallography and X-ray spectroscopy at cryogenic temperatures. In this report, we present the preliminary progress using an X-ray free-electron laser to determine simultaneously the light-induced protein dynamics via crystallography and the local chemistry that occurs at the catalytic centre using X-ray spectroscopy under functional conditions at room temperature. 相似文献
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Srinivasa T. Reddy Mohamad Navab G.M. Anantharamaiah Alan M. Fogelman 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2014,1841(1):162-167
Despite strong evidence that HDL-cholesterol levels predict atherosclerotic events in a population, attempts at using an HDL-based treatment strategy have not yet been successful. Most of the efforts to date have focused on raising plasma HDL-cholesterol levels. This brief review focuses on a different strategy, which is based on the use of 18-amino acid apoA-I mimetic peptides. The story of these peptides spans decades and illustrates the remarkable complexity of HDL-based treatment strategies, but suggests that such a strategy may still be successful. 相似文献
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锰胁迫对杠板归细胞超微结构的影响 总被引:1,自引:0,他引:1
锰是植物生长必需的微量元素,然而锰含量过高将影响酶活性、造成植物毒害,不同植物的锰耐性差异很大。杠板归(Polygonum perfoliatum L.)是一种生长在锰尾矿废弃地的耐性植物。通过温室培养,应用透射电子显微镜-能谱联用仪研究不同锰处理条件下(5,1000,10 000μmol/L)杠板归根、茎和叶细胞超微结构的变化和锰在叶细胞内可能的存在形式,结果表明:(1)生长介质锰含量为5μmol/L时,杠板归细胞超微结构未见异常;即使锰处理浓度为1000μmol/L时,杠板归根、茎和叶细胞结构依然完整,细胞器清晰可见,未见明显损伤;(2)当锰处理浓度为10000μmol/L时,杠板归细胞器未见缺失现象,但根细胞内线粒体数量减少,茎细胞叶绿体开始受损,叶细胞叶绿体膜结构出现破损,基粒片层结构减少,嗜锇颗粒数量明显减少;(3)与对照相比,1000μmol/L或10000μmol/L锰处理30 d,植物细胞内出现黑色团聚物。10000μmol/L锰处理条件下,杠板归叶细胞内和细胞间隙出现类似针状物质,这可能是杠板归体内锰积累和分布的形态之一。研究成果有助于阐明植物的锰耐性机制,为锰耐性植物筛选和废弃锰尾矿库生态重建提供科学参考。 相似文献
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Petr Martinek Josef Hedbávný Tomáš Kudláček Michal Šťasta Emanuel Kula 《Entomologia Experimentalis et Applicata》2020,168(8):635-643
The adaptation of insects to environmental changes can constitute a crucial factor in their development and activity. The response of Cabera pusaria L. (Lepidoptera: Geometridae) caterpillars to high manganese (Mn) concentrations in the diet was studied. Birch leaves were treated by dipping in MnCl2·4H2O solutions, thereby achieving Mn contents of 370 (T0), 695 (T1), 3 198 (T2), and 6 302 mg kg−1 (T3). The reactions were determined by observing caterpillar mortality, development time, food consumption, and pupal weight. Manganese concentrations in larval excrement, pupae, and food were determined. Manganese in the diet at unnaturally increased concentrations caused great stress for caterpillars. All individuals in the treatment with the highest Mn concentration (T3) died during rearing and successful pupation occurred in only four individuals in T2. Even in the case of caterpillars from T1 (twofold higher than T0) a negative reaction (increased food consumption and prolonged development) was recorded. We also determined significantly increased Mn concentration in pupae from T1 (T2 and T3 were not included in this evaluation due to mortality) and excrement (T1‒T3) compared with T0 having a natural Mn concentration. Caterpillars were seen to eliminate negatively acting dietary Mn by its translocation to excrement. However, the highest mortality rate in T2 and T3 and negative reactions of individuals in T1 very likely demonstrate energy insufficiency and the high energy requirements of Mn elimination mechanisms. 相似文献
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农田生态系统中 ,营养元素循环与平衡的研究已经受到许多学者的广泛关注 ,主要集中于N ,P ,K三要素的研究[1 ,2 ] 。微量元素养分循环的研究虽有一些报道[3 ,4] ,但主要集中于B和Zn元素 ,而对Mn的研究尚未见报道。微量元素Mn具有植物营养和污染危害双重作用。在我国 ,Mn肥的应用研究 ,包括肥效、施肥技术、丰缺诊断等已取得较大进展 ,Mn对环境污染及危害影响研究也取得了一些成果。随着Mn肥应用面积日益扩大 ,研究其在土壤 植物系统中循环与平衡 ,以维持Mn肥对作物适量供应 ,促进农田生态系统Mn肥的良性循环以及控制土… 相似文献
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Kirstie H. Stansfield Terry Jo Bichell Aaron B. Bowman Tomás R. Guilarte 《Journal of neurochemistry》2014,131(5):655-666
High levels of manganese (Mn) exposure decrease striatal medium spiny neuron (MSN) dendritic length and spine density, but the mechanism(s) are not known. The Huntingtin (HTT) gene has been functionally linked to cortical brain‐derived neurotrophic factor (BDNF) support of striatal MSNs via phosphorylation at serine 421. In Huntington's disease, pathogenic CAG repeat expansions of HTT decrease synthesis and disrupt transport of cortical–striatal BDNF, which may contribute to disease, and Mn is a putative environmental modifier of Huntington's disease pathology. Thus, we tested the hypothesis that changes in MSN dendritic morphology Mn due to exposure are associated with decreased BDNF levels and alterations in Htt protein. We report that BDNF levels are decreased in the striatum of Mn‐exposed non‐human primates and in the cerebral cortex and striatum of mice exposed to Mn. Furthermore, proBDNF and mature BDNF concentrations in primary cortical and hippocampal neuron cultures were decreased by exposure to Mn confirming the in vivo findings. Mn exposure decreased serine 421 phosphorylation of Htt in cortical and hippocampal neurons and increased total Htt levels. These data strongly support the hypothesis that Mn‐exposure‐related MSN pathology is associated with decreased BDNF trophic support via alterations in Htt.