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61.
The stability constants of the binary and the ternary complexes of Pu4+ have been measured for certain carboxylate and aminocarboxylate ligands in aqueous solution of I = 5.0 M (1 M perchloric acid + 4 M ionic strength perchlorate media) and temperatures of 0-45 °C by the solvent extraction technique. The stability constants of the binary and the ternary complexes increased with increased temperature. The complexation enthalpy and entropy of the binary Pu-Ox and the ternary Pu-EDTA-Ox and DGA complexes indicated the stability of these complexes is due to the highly favorable entropy contribution while complexation enthalpies either oppose complexation or are weakly favorable. 相似文献
62.
Eco-physiological responses of linseed (Linum usitatissimum) to salt and alkali stresses 总被引:1,自引:0,他引:1 下载免费PDF全文
《植物生态学报》2016,40(1):69
63.
We studied block of the internal pore of the ROMK1 inward-rectifier K+ channel by Mg2+ and five quaternary ammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrapentylammonium). The apparent affinity of these blockers varied as a function of membrane voltage. As a consequence, the channel conducted K+ current more efficiently in the inward than the outward direction; i.e., inward rectification. Although the size of some monovalent quaternary ammoniums is rather large, the zδ values (which measure voltage dependence of their binding to the pore) were near unity in symmetric 100 mM K+. Furthermore, we observed that not only the apparent affinities of the blockers themselves, but also their dependence on membrane voltage (or zδ), varied as a function of the concentration of extracellular K+. These results suggest that there is energetic coupling between the binding of blocking and permeating (K+) ions, and that the voltage dependence of channel blockade results, at least in part, from the movement of K+ ions in the electrical field. A further quantitative analysis of the results explains why the complex phenomenon of inward rectification depends on both membrane voltage and the equilibrium potential for K+. 相似文献
64.
An advanced electro-active dry adhesive,which was composed of a mushroom-shaped fibrillar dry adhesive array actuated by an Ionic Polymer Metal Composite (IPMC) artificial muscle reinforced with nitrogen-doped carbon nanocages (NCNCs),was developed to imitate the actuation of a gecko's toe.The properties of the NCNC-reinforced Nafion membrane,the electromechanical properties of the NCNC-reinforced IPMC,and the related electro-active adhesion ability were investigated.The NCNCs were uniformly dispersed in the 0.1 wt% NCNC/Nafion membrane,and there was a seamless connection with no clear interface between the dry adhesive and the IPMC.Our 0.1 wt% NCNC/Nafion-IPMC actuator shows a displacement and force that are 1.6-2 times higher than those of the recast Nafion-IPMC.This is due to the increased water uptake (25.39%) and tensile strength (24.5 MPa) of the specific 3D hollow NCNC-reinforced Nafion membrane,as well as interactions between the NCNCs and the sulfonated groups of the Nafion.The NCNC/Nafion-IPMC was used to effectively actuate the mushroom-shaped dry adhesive.The normal adhesion forces were 7.85 mN,12.1 mN,and 51.7 mN at sinusoidal voltages of 1.5 V,2.5 V,and 3.5 V,respectively,at 0.1 Hz.Under the bionic leg trail,the normal and shear forces were approximately 713.5 mN (159 mN·cm-2) and 1256.6 mN (279 mN·cm-2),respectively,which satisfy the required adhesion.This new electro-active dry adhesive can be applied for active,distributed actuation and flexible grip in robots. 相似文献
65.
脂肪酶在离子液体/超临界流体体系中的结构稳定性是影响其活性的重要因素。本文采用分子动力学方法分别研究了南极假丝酵母脂肪酶B(CALB)在离子液体CYPHOS IL-201/极性超临界流体CHF_3两相体系和离子液体CYPHOS IL-201/非极性超临界流体CO_2两相体系中的结构稳定性,揭示影响CALB结构稳定性的因素。研究结果表明,在超临界CHF_3中,CHF_3破坏蛋白维持α螺旋结构的氢键是蛋白结构不稳定的主要原因;在超临界CO_2中,CALB蛋白的结构紧密性降低,有序二级结构发生了变化,导致稳定性下降。离子液体和两种超临界流体均形成了两相体系,蛋白处于离子液体相中,离子液体不溶于超临界流体,但超临界流体部分进入离子液体相,降低了离子液体相的黏度。其中,相比于CYPHOS IL-201/CO_2体系,CYPHOS IL-201/CHF_3体系的黏度降低多。在离子液体CYPHOS IL-201与超临界流体(CHF_3、CO_2)形成的两相体系中,离子液体CYPHOS IL-201具有保护蛋白结构的作用,使CALB蛋白结构更加稳定。 相似文献
66.
Ion-exchange chromatography is the standard technique used for plasmid DNA purification, an essential molecular biology procedure. Non-ionic detergents (NIDs) have been used for plasmid DNA purification, but it is unclear whether Hofmeister series salts (HSS) change the solubility and phase separation properties of specific NIDs, enhancing plasmid DNA purification. After scaling-up NID-mediated plasmid DNA isolation, we established that NIDs in HSS solutions minimize plasmid DNA contamination with protein. In addition, large-scale NID/HSS solutions eliminated lipopolysaccharides (LPS) contamination of plasmid DNA more effectively than Qiagen ion-exchange columns. Large-scale NID isolation/NID purification generated increased yields of high-quality DNA compared to alkali isolation/column purification. This work characterizes how HSS enhance NID-mediated plasmid DNA purification, and demonstrates that NID phase transition is not necessary for LPS removal from plasmid DNA. Specific NIDs such as IGEPAL CA-520 can be utilized for rapid, inexpensive, and efficient laboratory-based large-scale plasmid DNA purification, outperforming Qiagen-based column procedures. 相似文献
67.
P. lanceolata andP. major were grown in culture solutions with nitrate or ammonium as the nitrogen source. Dry matter accumulation in the shoot was
faster with nitrate than with ammonium, whilst that of the roots was not affected by the nitrogen source. As a consequence,
the shoot-to-root ratio was lower with ammonium than with nitrate. InP. lanceolata, dry matter percentage of shoot and root tissue was lower with nitrate nutrition, suggesting better elongation growth than
with ammonium. However, in shoot tissue ofP. major the opposite was found. The rate of root respiration declined with time, and this was almost completely due to a declining
activity of the alternative path, which amounted to about 30–60% of total root respiration. Respiration via the cytochrome
path was for a part of time slightly increased by ammonium, whereas the activity of the alternative path was strongly enhanced.
The concentration of ethanol-soluble carbohydrates (SC) in the roots of both species was higher when nitrate was used, but
no difference in the concentration of starch was found. When the plants were transferred from one nitrogen source to the other,
many parameters, including the concentration of nitrate and chloride, and the shoot to root ratio, adjusted to the new situation
in both species.
Grassland Species Research Group, Publication no. 116. 相似文献
68.
Hyun-Hee Jang Arvind P. Jamakhandi Shane Z. Sullivan Chul-Ho Yun Paul F. Hollenberg Grover P. Miller 《Biochimica et Biophysica Acta - Proteins and Proteomics》2010,1804(6):1285-1293
As a promiscuous redox partner, the biological role of cytochrome P450 reductase (CPR) depends significantly on protein–protein interactions. We tested a hypothesized CPR docking site by mutating D113, E115, and E116 to alanine and assaying activity toward various electron acceptors as a function of ionic strength. Steady-state cytochrome c studies demonstrated the mutations improved catalytic efficiency and decreased the impact of ionic strength on catalytic parameters when compared to wild type. Based on activity toward 7-ethoxy-4-trifluoro-methylcoumarin, CYP2B1 and CPR favored formation of an active CYP2B1•CPR complex and inactive (CYP2B1)2•CPR complex until higher ionic strength whereby only the binary complex was observed. The mutations increased dissociation constants only for the binary complex and suppressed the ionic strength effect. Studies with a non-binding substrate, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) suggest changes in activity toward cytochrome c and CYP2B1 reflect alterations in the route of electron transfer caused by the mutations. Electrostatic modeling of catalytic and binding parameters confirmed the importance of D113 and especially the double mutant E115 and E116 as mediators in forming charge–charge interactions between CPR and complex partners. 相似文献
69.
Recombination Losses Above and Below the Transport Percolation Threshold in Bulk Heterojunction Organic Solar Cells 下载免费PDF全文
Aren Yazmaciyan Martin Stolterfoht Paul L. Burn Qianqian Lin Paul Meredith Ardalan Armin 《Liver Transplantation》2018,8(18)
Achieving the highest power conversion efficiencies in bulk heterojunction organic solar cells requires a morphology that delivers electron and hole percolation pathways for optimized transport, plus sufficient donor:acceptor contact area for near unity charge transfer state formation. This is a significant structural challenge, particularly in semiconducting polymer:fullerene systems. This balancing act in the model high efficiency PTB7:PC70BM blend is studied by tuning the donor:acceptor ratio, with a view to understanding the recombination loss mechanisms above and below the fullerene transport percolation threshold. The internal quantum efficiency is found to be strongly correlated to the slower carrier mobility in agreement with other recent studies. Furthermore, second‐order recombination losses dominate the shape of the current density–voltage curve in efficient blend combinations, where the fullerene phase is percolated. However, below the charge transport percolation threshold, there is an electric‐field dependence of first‐order losses, which includes electric‐field‐dependent photogeneration. In the intermediate regime, the fill factor appears to be limited by both first‐ and second‐order losses. These findings provide additional basic understanding of the interplay between the bulk heterojunction morphology and the order of recombination in organic solar cells. They also shed light on the limitations of widely used transport models below the percolation threshold. 相似文献
70.
A recent experiment on a physical, nonbiological system of ions at room temperature has proved that microscopic ion currents can be induced by applying simultaneously two parallel magnetic fields, one rather weak static field, (-->)B(0) and one much weaker alternating field, (-->) B(ac),[B(ac) approximately 10(-3) B(0)] whose frequency coincides with the cyclotron frequency v = qB(0)/2pim of the selected ion. As a result, ionic bursts lasting up to 20 s and with amplitude up to 10 nA arise. The much larger exchanges of energy induced by thermal agitation (the "kT-problem") appear to play no role whatsoever. We have analyzed this problem in the framework of coherent quantum electrodynamics, reaching the following conclusions: (a) as has been shown in previous articles, water molecules in the liquid and solute ions are involved in their ground state in coherent ordered configurations; (b) ions are able to move without collisions among themselves in the interstices between water coherence domains; (c) because of coherence, ions can follow classical orbits in the magnetic fields. A full quantitative understanding of the experiments is thus reached. 相似文献