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511.
Fadong Li Yaosen Ye Ruirui Cui Jun Zhang Cong Xu Hui Xu Gangyi Zhang Chaoyong Deng 《Luminescence》2023,38(9):1562-1571
A series of Mn4+-doped and Mn4+,K+-co-doped Ba2LaTaO6 (BLT) double-perovskite phosphors was synthesized using a high-temperature solid-state reaction. The phase purity and luminescence properties were also studied. The optimum doping concentration of Mn4+ and K+ was obtained by investigating the photoluminescence excitation spectra and photoluminescence emission spectra. The comparison of BLT:Mn4+ phosphors with and without K+ ions shows that the photoluminescence intensity of K+-doped phosphors was greatly enhanced. This is because there was a charge difference when Mn4+ ions were doped with Ta5+ ions in BLT. Mn4+–K+ ion pairs were formed after doping K+ ions, which hinders the nonradiative energy transfer between Mn4+ ions. Therefore, the luminescence intensity, quantum yield, and thermal stability of phosphors were enhanced. The electroluminescence spectra of BLT:Mn4+ and BLT:Mn4+,K+ were measured. The spectra showed that the light emitted from the phosphors corresponded well with chlorophyll a and phytochrome PR. The results show that the BLT:Mn4+,K+ phosphors had good luminescence properties and application prospects and are ideal materials for plant-illuminated red phosphors. 相似文献
512.
Atom-centered partial charges are calculated for the Fe-heme in cytochrome P450cam for use in molecular dynamics simulations of polar substrates bound in the active site of the enzyme. Charges are fit to the electrostatic potential produced by ab initio UHF wavefunctions for an Fe-porphine model. Basis set dependence of these charges is observed using the LANL1DZ, LANL2DZ and augmented 6–31G levels of theory. Upon geometry optimization of the enzyme, these charge sets cause varying degrees of distortion of the porphyrin from its crystallographically observed conformation. Scaling the charges calculated from the augmented 6–31G basis by 75% reduces the heme distortion while preserving reasonable interactions with a polar substrate. A comparison of the calculated charges with other published values is presented. 相似文献
513.
沙棘(Hippophae rhamnoides)是重要的雌雄异株人工林防护树种,但对其环境胁迫的性别响应差异研究不足,性别竞争与胁迫因子的交互效应响应特征尚不清楚。为了探讨锰胁迫和性别竞争交互处理下沙棘雌雄植株的生理响应特征和耐受能力,旨在为沙棘修复土壤重金属污染提供实践指导,该文研究了锰胁迫(4 000 mg·kg-1)和3种不同性别组合模式(雌雄、雌雌、雄雄)处理下沙棘的生理响应,分别测定雌雄沙棘叶片中叶绿素、过氧化物酶(peroxidase,POD)、超氧化物歧化酶(superoxide dismutase,SOD)、丙二醛(malondialdehyde,MDA)、总酚(total phenols, TP)、游离脯氨酸(free proline,Pro)、可溶性糖(soluble sugar,SS)、甜菜碱(glycine betaine, GB)以及锰含量。结果表明:(1)锰胁迫下,在所有竞争组合中,性间竞争的雄株(M/FM)SOD活性最高,而MDA含量与对照相比未有明显升高,表明雄株的抗氧化能力更好,膜氧化损伤程度更小。(2)锰胁迫时M/FM积累了更多的游离脯氨酸,表现出更好的渗透调节能力和耐受能力。(3)交互效应分析显示性别互作和锰胁迫交互处理显著影响了沙棘雌雄叶片的光合色素、抗氧化酶活性和渗透调节能力; 主成分分析显示SOD、POD、MDA、叶绿素b(chlorophyll b, Chlb)、SS、Pro可作为重要的生理响应指示参数。该研究结果对于利用沙棘修复土壤重金属污染可提供一定的参考。 相似文献
514.
Ruthenium red (RR) is known to be an inhibitor that binds to Ca2+ sites. It releases Ca2+ and Cl? together with the extrinsic polypeptide of 17 kDa associated with the oxygen evolving complex of photosystem II. In this work we used thermoluminescence to study S2/3QB? and S2QA? charge recombination. It is shown that RR produced a deeper inhibition of oxygen evolution compared with the effect of extrinsic polypeptide or Ca2+/Cl? depletion. Even though Mn is not released, the Mn cluster is disorganized by RR and the S1 → S2 transition is inhibited. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
515.
Culturing geranium at different doses of Zn from 0–1.0 g m–3 (Zn0 to Zn1.000) revealed that Zn is an antioxidant promoter, apart from its micronutrient essentiality. Zn0.250 was the critical concentration for maximum content (0.21 %) of total essential monoterpene oil(s). At Zn0.005-Zn0.250, net photosynthetic rate, and contents of chlorophyll and essential monoterpene oil(s) were affected. The maximum peroxidase activity was obtained at Zn0.250, with the production of biomolecule geraniol. We found an oxido-reducible reaction of Zn in the formation of monoterpene essential oil(s) and possibly major constituents of geraniol. 相似文献
516.
Ochiai T Asaoka T Kato T Osaka S Dewa T Yamashita K Gardiner AT Hashimoto H Nango M 《Photosynthesis research》2008,95(2-3):353-361
Synthetic single α-helix hydrophobic polypeptides, which have similar amino acid sequences to the hydrophobic core in the
native light-harvesting 1-β polypeptide from Rhodobacter sphaeroides, formed Zn porphyrin complexes on a gold electrode, as well as in n-octyl-β-glucoside micelles: this process is dependent on the structure of the pigments and the polypeptides. Interestingly,
an enhanced photoelectric current was observed when Zn mesoporphyrin monomer complexed with the synthetic light-harvesting
model polypeptide in an α-helical configuration was assembled with a defined orientation onto the electrode. Analog of these
light-harvesting model complexes are also useful in providing insights into the effect of polypeptide structure on the formation
of light-harvesting complexes on and off electrodes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
517.
Two water-soluble ferric porphyrins, sodium 5α,10β,15α,20β-tetrakis(2-(sulfonatoacetamido)phenyl)porphyrinatoiron(III) (FeIIITanP) and 5α,10β,15α,20β-tetrakis(2-(N,N,N-trimethylammoniumacetamido)phenyl)porphyrinatoiron(III) chloride (FeIIITcatP), were synthesized. The pKa values of the coordinated H2O of FeIIITanP and FeIIITcatP were evaluated to be 8.0 and 4.1, respectively. Reactions of NO with the ferric porphyrins were examined spectrophotometrically in aqueous solution. Porphyrin FeIIITanP binds NO reversibly to give the corresponding ferric NO species at pH 1.3 and pH 3.0, and FeIIITcatP reacts similarly with NO at pH 1.3. The thermodynamic data for the NO binding were estimated from van't Hoff plots. At pH 3.0, visible and ESR spectral data indicated that FeIIITcatP binds NO reversibly to produce ferrous NO species depending on NO partial pressures. These results were discussed based on through-space intramolecular interactions between the coordinated H2O or NO and the ionic substituents of the porphyrins. 相似文献
518.
519.
Rice tolerance to excess Mn: Implications in the chloroplast lamellae and synthesis of a novel Mn protein 总被引:1,自引:0,他引:1
Rice (Oryza sativa L. cv. Safari) plants were grown over a 21-d period in nutrient solutions containing Mn concentrations varying between 0.125 and 32 mg·L–1. The plant shoots and the thylakoid membranes showed similar overall Mn increases for this range of treatments, but different accumulation kinetics. It was found that the highest Mn treatment were associated to the synthesis of a new thylakoid protein with an average molecular mass of 36.5 kDa and a Mn:protein ratio of about 1. This protein exhibited superoxide dismutase activity, as well as a high content of Gln, Asp, Glu, Leu and Gly. Its EPR spectrum is characteristic of high-spin Mn(II), in a S=5/2 ground state. A comparative study of SDS polyacrylamide gel profiles of thylakoid polypeptides from the various treatments disclosed quantitative changes, as well as a new 37/36-kDa polypeptide band in the two highest Mn treatments. The photosynthetic electron transport rates coupled to PSII and PSI showed a significant increase until the 8-mg·L–1 Mn treatment. The related superoxide production of thylakoids (monitored by EPR spectroscopy) showed minimum values from the 0.5-mg·L–1 Mn treatment onwards, which, as shown by the thiobarbituric acid reaction was coupled to a non-significant variation of the acyl lipid peroxidation. It was concluded that Oryza sativa L. cv. safari has a high internal tolerance to Mn as it synthesises a new manganese protein that mimics superoxide dismutase functioning. 相似文献
520.
Experiments were performed on the freshwater amphipod Paramelita nigroculus to determine the route of uptake for Al, Cu and Mn. The extent of correlation between the concentrations of Al, Cu and Mn and those of macro-cations Na, Ca and Mg was investigated in order to determine appropriate strategies of water quality management. Indeed, active uptake of toxicants can be controlled by disturbing the active pump used. After 21 days of exposure to different combined concentrations, survivors were analysed chemically by ICP-S after depuration, drying, ashing and digestion with concentrated nitric acid.The results showed significant correlations between the concentrations of major cations and the three metals under study (i.e. Al, Cu and Mn) at p < 0.05. These are Ca vs Al, Ca vs Mg, Na vs Mg, Na vs Mn, Al vs Mg, Al vs Cu, and Mg vs Mn. No other combination showed significant correlation. High r-values for Na vs Mg (r=0.7194) and for Na vs Mn (r=0.6253), as well as low concentrations of Mg and Mn, suggest interactions between the active uptake of Mn and Mg, although there may be interferences due to the use of Na pump. Additional experiments examined the type of interaction occurring when Mn and Mg were present in 1:1 mixtures in water. The Student's t test showed that observed differences in bioaccumulation of Mn, when alone and when combined, were not statistically significant at p < 0.05. These differences may be attributed to chance but not to the presence of Mg in the medium; while differences in bioaccumulation of Mg, when alone and when combined, were statistically significant at p < 0.002. These were attributed to Mn, which lowers Mg uptake by P. nigroculus. 相似文献