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1.
Manuela Grotjahn Norbert Jäger Hans-Joachim Drexler Hans-Jürgen Holdt Erich Kleinpeter 《Journal of molecular modeling》1999,5(3):72-77
Maleonitrile-dithiacrown ethers mn-12S2O2 - mn-21S2O5 (mn = maleonitrile) are preorganized S2On+1-coronands (n = 1–4) which force B, AB and A class metal ions into mixed S/O coordination spheres. Moreover, they form chelate complexes with MX2 salts (M = Pd, Pt; X = Cl, Br), which were studied in this paper. The structures of mn-S2On+1 and [PtCl2(mn-S2On+1)] (n = 2, 3) were investigated theoretically by empirical and semiempirical methods using SYBYL (TRIPOS force field) and MSI/DISCOVER97 (ESFF force field). mn-12S2O2 was investigated experimentally by X-ray analysis and 1D and 2D NMR spectroscopy in solution and the complex formation was studied by 1H, 13C and 195Pt NMR titration experiments, respectively. S-inversion was also investigated in order to determine the ring corresponding interconversional barriers. Different orientations of the macrocyclic ring system mn-18S2O4 and of its transition states are shown.Electronic Supplementary Material available. 相似文献
2.
The cathodic electrochemiluminescence (ECL) of peroxydisulphate (S2O82?)–ciprofloxacin (CPF) system at a wax‐impregnated graphite electrode was studied. When CPF was absent, S2O82? was electrochemically reduced to sulphate free radical (SO4??), and dissolved oxygen absorbed on the electrode surface was reduced to protonated superoxide anion radical (HO2?). The HO2? was oxidized by SO4?? to produce molecular oxygen in both singlet and triplet states. Some of the singlet molecular oxygen (1O2) further combined through collision to be an energy‐rich precursor singlet molecular oxygen pair (1O2)2. A weak ECL was produced when 1O2 or (1O2)2 was converted to ground‐state molecular oxygen (3O2). When CPF was present, a stronger ECL was produced, which originated from two emitting species. The main emitting species was excited state CPF (CPF*), which was produced by accepting energy from (1O2)2. The other emitting species was excited singlet molecular oxygen pair [(1O2)2*], which originated from the chemical oxidation of CPF by SO4?? and dissolved oxygen. Based on the stronger ECL phenomenon, an ECL method for the determination of either S2O82? or CPF was proposed. The proposed ECL method has been applied to the determination of CPF in pharmaceutical preparations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
3.
Maxim A. Ivanov Vladimir V. Sharutin Antonya P. Pakusina Willis Forsling 《Inorganica chimica acta》2007,360(9):2897-2904
O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C6H5)4{S2P(OR)2}] (R = C3H7, i-C4H9) were prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate ligands in their molecular structures (i.e., S,S′-bidentate chelating and S-unidentately coordinated, respectively). To characterise quantitatively phosphorus sites in both species of dithiophosphate ligands, 31P chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in MAS NMR spectra. The 31P chemical shift tensors for the bidentate chelating and unidentately coordinated dithiophosphate ligands display a profoundly rhombic and nearly axially symmetric characters, respectively. 相似文献
4.
A remediation process for heavy metal polluted sediment has previously been developed in which the heavy metals are removed from the sediment by solid‐bed bioleaching using elemental sulfur (S0): the added S0 is oxidized by the indigenous microbes to sulfuric acid that dissolves the heavy metals which are finally extracted by percolating water. In this process, the temperature is a factor crucially affecting the rate of S0 oxidation and metal solubilization. Here, the effect of temperature on the kinetics of S0 oxidation has been studied: oxidized Weiße Elster River sediment (dredged near Leipzig, Germany) was mixed with 2 % S0, suspended in water and then leached at various temperatures. The higher the temperature was, the faster the S0 oxidized, and the more rapid the pH decreased. But temperatures above 35 °C slowed down S0 oxidation, and temperatures above 45 °C let the process – after a short period of acidification to pH 4.5 – stagnate. The latter may be explained by the presence of both neutrophilic to less acidophilic thermotolerant bacteria and acidophilic thermosensitive bacteria. Within 42 days, nearly complete S0 oxidation and maximum heavy metal solubilization only occurred at 30 to 45 °C. The measured pH(t) courses were used to model the rate of S0 oxidation depending on the temperature using an extended Arrhenius equation. Since molecular oxygen is another factor highly influencing the activity of S0‐oxidizing bacteria, the effect of dissolved O2 (controlled by the O2 content in the gas supplied) on S0 oxidation was studied in suspension: the indigenous S0‐oxidizing bacteria reacted quite tolerant to low O2 concentrations; the rate of S0 oxidation – measured as the specific O2 consumption – was not affected until the O2 content of the suspension was below 0.05 mg/L, i.e., the S0‐oxidizing bacteria showed a high affinity to O2 with a half‐saturation constant of about 0.01 mg/L. Stoichiometric coefficients describing the relationship between the mass of S0, O2 and CO2 consumed are scarcely available. The growth of S0‐oxidizing, obligate aerobic, autotrophic bacteria was, therefore, stoichiometrically balanced (by using a yield coefficient of YX/S = 0.146 g cells/g S0, calculated with data from the literature): 24.14 S0 + 29.21 O2 + 27.14 H2O + 5 CO2 + NO3–→ C5H7O2N + 24.14 SO42– + 47.28 H+, which resulted in Y = 1.21 g O2/g S0 and Y = 0.28 g CO2/g S0. 相似文献
5.
Se Wang Ce Hao Zhanxian Gao Jingwen Chen Jieshan Qiu 《Journal of molecular modeling》2013,19(4):1913-1918
Intramolecular and intermolecular hydrogen bonding in electronic excited states of calixarene building blocks bis(2-hydroxyphenyl)methane (2HDPM) monomer and hydrogen-bonded 2HDPM-H2O complex were studied theoretically using the time-dependent density functional theory (TDDFT). Twenty-four stable conformations (12 pairs of enantiomers) of 2HDPM monomer have been found in the ground state. From the calculation results, the conformations 1a and 1b which both have an intramolecular hydrogen bond are the most stable ones. The infrared spectra of 2HDPM monomer and 2HDPM-H2O complex in ground state and S1 state were calculated. The stretching vibrational absorption band of O2???H3 group in the monomer and complex disappeared in the S1 state. At the same time, a new strong absorption band appeared at the C=O stretching region. From the calculation of bond lengths, it indicates that the O2???H3 bond is significantly lengthened in the S1 state. However, the C1???O2 bond is drastically shortened upon electronic excitation to the S1 state and has the characteristics of C=O band. Furthermore, the intramolecular hydrogen bond O2???H3?·?·?·?O4 of the 2HDPM monomer and the intermolecular hydrogen bonds O2???H3?·?·?·?O7 and O7???H9?·?·?·?O4 of 2HDPM-H2O complex are all shortened and strengthened in the S1 state. Figure
Intramolecular and intermolecular hydrogen bonding in electronic excited states of calixarene building blocks bis(2-hydroxyphenyl)methane (2HDPM) monomer and hydrogen-bonded 2HDPM-H2O complex were studied by TDDFT method 相似文献
6.
Bazylinski DA Dean AJ Williams TJ Long LK Middleton SL Dubbels BL 《Archives of microbiology》2004,182(5):373-387
Magnetite-producing magnetotactic bacteria collected from the oxic–anoxic transition zone of chemically stratified marine environments characterized by O2/H2S inverse double gradients, contained internal S-rich inclusions resembling elemental S globules, suggesting they oxidize reduced S compounds that could support autotrophy. Two strains of marine magnetotactic bacteria, MV-1 and MV-2, isolated from such sites grew in O2-gradient media with H2S or thiosulfate (S2O32–) as electron sources and O2 as electron acceptor or anaerobically with S2O32– and N2O as electron acceptor, with bicarbonate (HCO3–)/CO2 as sole C source. Cells grown with H2S contained S-rich inclusions. Cells oxidized S2O32– to sulfate (SO42–). Both strains grew microaerobically with formate. Neither grew microaerobically with tetrathionate (S4O62–), methanol, or Fe2+ as FeS, or siderite (FeCO3). Growth with S2O32– and radiolabeled 14C-HCO3– showed that cell C was derived from HCO3–/CO2. Cell-free extracts showed ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity. Southern blot analyses indicated the presence of a form II RubisCO (cbbM) but no form I (cbbL) in both strains. cbbM and cbbQ, a putative post-translational activator of RubisCO, were identified in MV-1. MV-1 and MV-2 are thus chemolithoautotrophs that use the Calvin–Benson–Bassham pathway. cbbM was also identified in Magnetospirillum magnetotacticum. Thus, magnetotactic bacteria at the oxic–anoxic transition zone of chemically stratified aquatic environments are important in C cycling and primary productivity. 相似文献
7.
Qi-An Sun Benlian Wang Masaru Miyagi Douglas T. Hess Jonathan S. Stamler 《The Journal of biological chemistry》2013,288(32):22961-22971
In mammalian skeletal muscle, Ca2+ release from the sarcoplasmic reticulum (SR) through the ryanodine receptor/Ca2+-release channel RyR1 can be enhanced by S-oxidation or S-nitrosylation of separate Cys residues, which are allosterically linked. S-Oxidation of RyR1 is coupled to muscle oxygen tension (pO2) through O2-dependent production of hydrogen peroxide by SR-resident NADPH oxidase 4. In isolated SR (SR vesicles), an average of six to eight Cys thiols/RyR1 monomer are reversibly oxidized at high (21% O2) versus low pO2 (1% O2), but their identity among the 100 Cys residues/RyR1 monomer is unknown. Here we use isotope-coded affinity tag labeling and mass spectrometry (yielding 93% coverage of RyR1 Cys residues) to identify 13 Cys residues subject to pO2-coupled S-oxidation in SR vesicles. Eight additional Cys residues are oxidized at high versus low pO2 only when NADPH levels are supplemented to enhance NADPH oxidase 4 activity. pO2-sensitive Cys residues were largely non-overlapping with those identified previously as hyperreactive by administration of exogenous reagents (three of 21) or as S-nitrosylated. Cys residues subject to pO2-coupled oxidation are distributed widely within the cytoplasmic domain of RyR1 in multiple functional domains implicated in RyR1 activity-regulating interactions with the L-type Ca2+ channel (dihydropyridine receptor) and FK506-binding protein 12 as well as in “hot spot” regions containing sites of mutation implicated in malignant hyperthermia and central core disease. pO2-coupled disulfide formation was identified, whereas neither S-glutathionylated nor sulfenamide-modified Cys residues were observed. Thus, physiological redox regulation of RyR1 by endogenously generated hydrogen peroxide is exerted through dynamic disulfide formation involving multiple Cys residues. 相似文献
8.
《Saudi Journal of Biological Sciences》2019,26(4):849-853
The K2S2O8 assisted photocatalytic system was applied for treating refractory petrochemical wastewater. Co-TiO2/zeolite catalyst synthesized by sol-gel method was demonstrated to possess a good activity towards mineralization of the refractory petrochemical wastewater in the K2S2O8 assisted photocatalytic system. Orthogonal design was employed to optimize the reaction parameters, according to the results, K2S2O8 dosage was the most prominent impact factor. More experiments were conducted to further enhance the COD removal efficiency. In consideration of both efficiency and costs, the petrochemical wastewater was treated in the K2S2O8 assisted photocatalytic system at pH 4, K2S2O8 dosage 2.03 g/L, catalyst amount 250 g/L with irradiation by 1 lamp and aeration. The COD removal efficiency reached up to 93.4% with a rate constant of 1.14 × 10−2 per min, and Co-TiO2/zeolite showed a good stability towards the K2S2O8 assisted photocatalytic degradation of petrochemical wastewater. 相似文献
9.
We studied the composition of molecular forms of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in normal and streptozotocin-induced diabetic rat retinas. Tissues were sequentially extracted with saline (S1) and saline-detergent buffers (S2). 50% decrease in the amphiphilic G4 and G1 AChE molecular forms was observed in the diabetic retina compared to the controls. Less than 5% of the cholinesterase activity was due to BChE. 60% of the BChE activity in normal retina was brought into solution and evenly distributed between S1 and S2. In spite of the low BChE activity in the retina it was possible to detect globular forms (GA
1, GA
2, GA
4, GH
4) and a small proportion of an asymmetric form (A12) in the S1 extract. The GA
4 and GA
1 forms were found in the S2 extract. In the diabetic retina the activity of GA
4 and GA
1 BChE molecular forms was reduced 60% and 40% respectively. Our results indicate that diabetes caused a remarkable decrease in the activity of cholinesterase molecular forms in the retina. These decrease might participate in the alterations observed in the diabetic retina. 相似文献
10.
《Inorganica chimica acta》1988,147(1):27-31
The electrochemistry for the reduction of tetrakis(dialkyl- and diphenyldithiocarbamato)-μ-oxodioxodirhenium complexes trans-Re2O3(S2CNR2)4 (R = methyl, ethyl, propyl, butyl and phenyl) was investigated in seven nonaqueous solvents. The complexes underwent a reversible reduction involving one- electron at a platinum electrode to [Re2O3(S2CNR2)4]−, which decomposed with the cleavage of the μ-oxo bridge to form ReO(S2CNR2)2, R2CNS2− and other rhenium complexes. The redox potential Eo′ of [Re2O3(S2CNR2)4]0/− couples and the stability of the reduction product [Re2O3(S2CNR2)4]− depend on the R group. The Eo′ are appreciably solvent-dependent. The difference in Eo′ with solvents could be interpreted in terms of the solubility parameters. 相似文献
11.
《BBA》1986,850(1):21-32
Wheat O2-evolving Photosystem II (PS II) membranes having a PS II unit of approx. 200 chlorophylls (Chl), approx. 4 Mn/200 Chl, less than 1 P-700/3000 Chl and an electron-acceptor pool of approx. 2.5 equiv./PS II were analyzed and compared with wheat PS II membranes depleted (at least 90%) of the 17 and 23 kDa proteins by NaCl extraction during Triton X-100 isolation of membranes. Extraction of these proteins caused approx. 50% decrease in O2 evolution in any light regime and an increase of approx. 2 equiv./PS II of the electron-acceptor pool, but affected neither Mn abundance, photoreduction of DCIP by tetraphenylboron, or N2 yield (from NH2OH) from a single flash. Mass spectrometric analyses of O2 flash yields in the presence of potassium ferricyanide showed that both chloroplasts and the unextracted PS II membranes yielded oscillations compatible with S0/S1/S2/S3 of 25:75:0:0 and α (0.1) and β (0.05). Depletion of 17 and 23 kDa proteins resulted in a two-fold increase in α, approx. 25–40% disconnection of the S state complex from the PS II trap complex but with no change in β. Preincubation of control or extracted PS II membranes with potassium ferricyanide permitted a significant double-hit on the first flash. In the absence of an added electron acceptor, N2 flash yields were more sustained with 17 and 23 kDa depleted than with 17 and 23 kDa sufficient PS II membranes. In contrast, no significant O2 flash yields were observed with extracted PS II preparations under these conditions (control PS II membranes showed a predictable O2 pattern before damping after only 5–6 flashes). These results suggest that extraction of the 17 and 23 kDa proteins results in an increase of pool size on the PS II acceptor side (seen as unmasking ‘Component C’). ‘Component C’ can mediate electron transfer from Q− to Z+ (S2). 相似文献
12.
Heparin inhibition and polyamine stimulation of a glycogen synthase kinase (PC0.7) from rabbit skeletal muscle 总被引:3,自引:0,他引:3
Molecular motion of 1,6-diphenyl-1,3,5-hexatriene embedded in intact guinea pig alveolar macrophage membranes was investigated by using techniques of nanosecond timeresolved fluorescence anisotropy measurements in the temperature range of 0–50 °C, and as a function of benzyl alcohol concentration. It was shown that molecular arrangement and microheterogeneity of the hydrocarbon region surrounding 1,6-diphenyl-1,3,5-hexatriene molecules are dependent on the temperature and benzyl alcohol concentration. The lipid orientation order parameter, Sv, showed a discontinuity in the temperature range 12–40 °C, which may indicate a phase transition. N-Formylmethionylphenylalanine-stimulated production of O2? from macrophages increased with temperature parallel with changes in Sv. Benzyl alcohol decreases the magnitude of the lipid order parameter at all temperatures studied. In the same concentration range of benzyl alcohol, stimulated O2? production by macrophages was inhibited. These data show the complex relationship between lipid integrity in macrophage membranes and a physiological function of these cells. In addition, the results indicate that benzyl alcohol influences the integrity of both the protein and lipid hydrophobic regions of the membrane. 相似文献
13.
An Open‐Structured Matrix as Oxygen Cathode with High Catalytic Activity and Large Li2O2 Accommodations for Lithium–Oxygen Batteries
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Xiaodong Lin Ruming Yuan Senrong Cai Youhong Jiang Jie Lei San‐Gui Liu Qi‐Hui Wu Hong‐Gang Liao Mingsen Zheng Quanfeng Dong 《Liver Transplantation》2018,8(18)
The nonaqueous lithium–oxygen (Li–O2) battery is considered as one of the most promising candidates for next‐generation energy storage systems because of its very high theoretical energy density. However, its development is severely hindered by large overpotential and limited capacity, far less than theory, caused by sluggish oxygen redox kinetics, pore clogging by solid Li2O2 deposition, inferior Li2O2/cathode contact interface, and difficult oxygen transport. Herein, an open‐structured Co9S8 matrix with sisal morphology is reported for the first time as an oxygen cathode for Li–O2 batteries, in which the catalyzing for oxygen redox, good Li2O2/cathode contact interface, favorable oxygen evolution, and a promising Li2O2 storage matrix are successfully achieved simultaneously, leading to a significant improvement in the electrochemical performance of Li–O2 batteries. The intrinsic oxygen‐affinity revealed by density functional theory calculations and superior bifunctional catalytic properties of Co9S8 electrode are found to play an important role in the remarkable enhancement in specific capacity and round‐trip efficiency for Li–O2 batteries. As expected, the Co9S8 electrode can deliver a high discharge capacity of ≈6875 mA h g?1 at 50 mA g?1 and exhibit a low overpotential of 0.57 V under a cutoff capacity of 1000 mA h g?1, outperforming most of the current metal‐oxide‐based cathodes. 相似文献
14.
Ichiro Hayakawa Akiyuki Ikedo Takumi Chinen Takeo Usui Hideo Kigoshi 《Bioorganic & medicinal chemistry》2012,20(19):5745-5756
Various analogues of glaziovianin A, an antitumor isoflavone, were synthesized, and their biological activities were evaluated. O7-modified glaziovianin A showed strong cytotoxicity against HeLa S3 cells. Compared to glaziovianin A, the O7-benzyl and O7-propargyl analogues were more cytotoxic against HeLa S3 cells and more potent M-phase inhibitors. Furthermore, O7-modified molecular probes of glaziovianin A were synthesized for biological studies. 相似文献
15.
Shinro Mashiko Nobutaka Suzuki Satoshi Koga Minoru Nakano Toshio Goto Toshihiko Ashino Iwao Mizumoto Humio Inaba 《Luminescence》1991,6(2):69-72
The rate constants for [1O2] [MCLA] and [1O2][NaN3] were measured by quenching the near-infrared emission (1Δg→3∑g) in steady state with MCLA and NaN3, respectively. 1O2 was constantly generated by energy transfer to O2 from Ar laser-excited Rose Bengal. The Stern—Volmer plots yielded the second-order rate constants of 2.94 × 109 M?1 S?1 and 3.83 × 108 M?1 S?1 for quenching 1O2 with MCLA and NaN3 in water at pH 5.4, respectively. The 1O2 + MCLA reaction emitted light with maximum at 465 nm at pD 4.5 identical to the O2? + MCLA reaction. 相似文献
16.
Activated persulfate oxidation technologies based on sulfate radicals were first evaluated for defluorination of aqueous perfluorooctanesulfonate (PFOS). The influences of catalytic method, time, pH and K2S2O8 amounts on PFOS defluorination were investigated. The intermediate products during PFOS defluorination were detected by using LC/MS/MS. The results showed that the S2O8
2− had weak effect on the defluorination of PFOS, while the PFOS was oxidatively defluorinated by sulfate radicals in water. The defluorination efficiency of PFOS under various treatment was followed the order: HT (hydrothermal)/K2S2O8 > UV (ultraviolet)/K2S2O8 > Fe2+/K2S2O8 > US (ultrasound)/K2S2O8. Low pH was favorable for the PFOS defluorination with sulfate radicals. Increase in the amount of S2O8
2− had positive effect on PFOS defluorination. However, further increase in amounts of S2O8
2− caused insignificant improvement in PFOS defluorination due to elimination of sulfate radicals under high concentration of S2O8
2−. CF3(CF2)nCOOH (n = 0–6) were detected as intermediates during PFOS defluorination. Sulfate radicals oxidation and hydrolysis were the main mechanisms involved in defluorination process of PFOS. 相似文献
17.
Peng Wang Caixia Li Shihua Dong Xiaoli Ge Peng Zhang Xianguang Miao Rutao Wang Zhiwei Zhang Longwei Yin 《Liver Transplantation》2019,9(24)
The critical challenges of Li‐O2 batteries lie in sluggish oxygen redox kinetics and undesirable parasitic reactions during the oxygen reduction reaction and oxygen evolution reaction processes, inducing large overpotential and inferior cycle stability. Herein, an elaborately designed 3D hierarchical heterostructure comprising NiCo2S4@NiO core–shell arrays on conductive carbon paper is first reported as a freestanding cathode for Li‐O2 batteries. The unique hierarchical array structures can build up multidimensional channels for oxygen diffusion and electrolyte impregnation. A built‐in interfacial potential between NiCo2S4 and NiO can drastically enhance interfacial charge transfer kinetics. According to density functional theory calculations, intrinsic LiO2‐affinity characteristics of NiCo2S4 and NiO play an importantly synergistic role in promoting the formation of large peasecod‐like Li2O2, conducive to construct a low‐impedance Li2O2/cathode contact interface. As expected, Li‐O2 cells based on NiCo2S4@NiO electrode exhibit an improved overpotential of 0.88 V, a high discharge capacity of 10 050 mAh g?1 at 200 mA g?1, an excellent rate capability of 6150 mAh g?1 at 1.0 A g?1, and a long‐term cycle stability under a restricted capacity of 1000 mAh g?1 at 200 mA g?1. Notably, the reported strategy about heterostructure accouplement may pave a new avenue for the effective electrocatalyst design for Li‐O2 batteries. 相似文献
18.
F.B Jensen T LecklinM Busk N.R BuryR.W Wilson C.M WoodM Grosell 《Journal of experimental marine biology and ecology》2002,274(2):159-174
Blood respiratory, acid-base, and ionic changes in response to hyperosmotic shock were studied in vivo and in vitro in the European flounder. One primary aim was to evaluate regulatory changes in red blood cell (RBC) volume and its interrelationship with blood O2 transporting properties. An acute increase in the ambient salinity from 10 to 30 ppt caused small but significant increases in extracellular osmolality (<20 mosM kg−1), [Na+], and [Cl−], which were corrected within 48 h. RBC volume was not significantly changed 3 h after the in vivo exposure to elevated salinity. A small metabolic acidosis was fully developed within 3 h, and this acidosis seemed responsible for a modest decrease in blood O2 affinity (i.e., increased P50-O2 tension at 50% O2 saturation). RBC organic phosphates were unchanged. In vitro elevation of whole blood extracellular osmolality by 60 mosM kg−1 caused immediate RBC shrinkage. The subsequent regulatory volume increase (RVI) showed a graded dependency on blood O2 saturation (SO2). At SO2 values of 0% and 20%, there were full RBC volume recoveries within 120 min, RVI was partial at SO2 values of 45% and 55%, and RVI was absent at a SO2 of 100%. SO2 and P50 did not change significantly during RBC shrinkage and RVI. Thus, the up-concentration of cellular haemoglobin and organic phosphates in hyperosmotically shrunken RBCs had minimal influence on blood O2 transporting properties. The degree of cell shrinkage and time needed for RVI were positively correlated with the magnitude of the rise in extracellular osmolality. The RVI proceeded via elevation of cellular [Na+], [Cl−], and to some extent also [K+]. Cell volume regulatory mechanisms are only needed to correct minor volume disturbances in vivo, because changes in extracellular osmolality were limited by an efficient osmotic regulation at the epithelial interface between extracellular compartment and environment. 相似文献
19.
Li-Ping Ding Xiao-Yu Kuang Peng Shao Ming-Min Zhong 《Journal of molecular modeling》2013,19(4):1527-1536
The structural, electronic and magnetic properties of neutral and anion Fe2S2, Fe3S4 and Fe4S4 have been investigated with the aid of previous photoelectron spectroscopy and density functional theory calculations. Theoretical electron detachment energies (both vertical and adiabatic) of anion clusters for the lowest energy structure were computed and compared with the experimental results to verify the ground states. The optimized structures show that the ground state structures of Fe2S2 0/?, Fe3S4 0/? and Fe4S4 0/? favor high spin state and are similar to their structures in proteins. The electron delocalization pattern for all the clusters and the nature of bonding between Fe and S atoms were studied by analyzing molecular orbitals. Natural population analysis demonstrates that Fe atoms act as an electron donor in all clusters, and the electron density difference map clearly shows the direction of the electron flow over the whole complex. Furthermore, the investigated magnetism shows that the Fe atoms carried most of the magnetic moments, which is due mainly to the 3d state, while only very small magnetic moments are found on S atoms. 相似文献
20.
Carlos Garcia-Mata Jianwen Wang Pawel Gajdanowicz Wendy Gonzalez Adrian Hills Naomi Donald Janin Riedelsberger Anna Amtmann Ingo Dreyer Michael R. Blatt 《The Journal of biological chemistry》2010,285(38):29286-29294
Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca2+ and K+ channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K+ channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H2O2. We show that H2O2 rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H2O2 and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H2O2-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys168 located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H2O2. The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys168 as a critical target for H2O2, and implicate ROS-mediated control of the K+ channel in regulating mineral nutrient partitioning within the plant. 相似文献