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1.
V. A. Belyaev D. A. Kozlov A. A. Terent’ev A. E. Trenin 《Plasma Physics Reports》2017,43(10):1039-1041
A method for determining the lifetime of unstable ions is described. The method is based on measuring the decrease in the ion beam current onto a fixed detector with increasing path length of the ion beam from the ion source to the detector. The measurements performed for D? 2 and HD? molecular ions have shown that their lifetimes are 3.5 ± 0.1 and 4.4 ± 0.1 μs, respectively. 相似文献
2.
Tessari F Bortolami S Zoccarato F Alexandre A Cavallini L 《Journal of bioenergetics and biomembranes》2011,43(3):267-274
Sodium Nitroprusside (SNP) and S-Nitrosoglutathione (GSNO) differently affect mitochondrial H2O2 release at Complex-I. mM SNP increases while GSNO decreases the release induced by succinate alone or added on top of NAD-linked
substrates. Stimulation likely depends on Nitric Oxide (
.
NO) (released by SNP but not by GSNO) inhibiting cytochrome oxidase and mitochondrial respiration. Preincubations with SNP
or high GSNO (10 mM plus DTE to increases its
.
NO release) induces an inhibition of the succinate dependent H2O2 production consistent with a
.
NO dependent covalent modification. However maximal inhibition of the succinate dependent H2O2 release is obtained in the presence of low GSNO (20–100 μM), but not with SNP. This inhibition appears independent of
.
NO release since μM GSNO does not affect mitochondrial respiration, or the H2O2 detection systems and its effect is very rapid. Inhibition may be partly due to an increased removal of O2.− since GSNO chemically competes with NBT and cytochrome C in O2.− detection. 相似文献
3.
Franco Zoccarato Lucia Cavallini Adolfo Alexandre 《Journal of bioenergetics and biomembranes》2009,41(4):387-393
Mitochondrial production of H2O2 is low with NAD substrates (glutamate/pyruvate, 3 and 2 mM) (G/P) and increases over ten times upon further addition of succinate,
with the formation of a sigmoidal curve (semimaximal value at 290 μM, maximal H2O2 production at 600 μM succinate). Malate counteracts rapidly the succinate induced increased H2O2 release and moves the succinate dependent H2O2 production curve to the right. Nitric oxide (NO) and carbon monoxide (CO) are cytochrome c oxidase inhibitors which increase
mitochondrial ROS production. Cyanide (CN−) was used to mimic NO and CO. In the presence of G/P and succinate (300 μM), CN− progressively increased the H2O2 release rate, starting at 1.5 μM. The succinate dependent H2O2 production curve was moved to the left by 30 μM CN−. The Vmax was little modified. We conclude that succinate is the controller of mitochondrial H2O2 production, modulated by malate and CN−. We propose that succinate promotes an interaction between Complex II and Complex I, which activates O2− production. 相似文献
4.
The structures and stabilities of eleven N13
+ and N13
– isomers have been investigated with second-order Møller–Plesset (MP2) and density functional theory (DFT) methods. Five N13
+ isomers and six N13
– isomers are all reasonable local minima on their potential energy hypersurfaces. The most stable N13
+ cation is structure C-2 with C2v symmetry, which contains a pentazole ring and two N4 open chains. It is different from those of the N7
+ and N9
+ clusters, but similar to the N11
+ cluster. Meanwhile, the most stable N13
– structure A-2 is composed of a pentazole ring and a six-membered ring connected by two nitrogen atoms. It is not only different from those of the N7
– and N9
– clusters, but also from the N11
– cluster. The decomposition pathways of structures C-2 and A-2 were investigated at the B3LYP/(aug)-cc-pVDZ level. From the barrier heights of the structures C-2 and A-2 decomposition processes, it is suggested that C-2 is difficult to observe experimentally and A-2 may be observed as a short-lived species.
Figure Optimized geometrical parameters of N13
+ isomer C-2
相似文献
5.
D. Koulougliotis 《Photosynthetica》2009,47(4):567-574
Progressive microwave power saturation (P1/2) measurements have been performed on the tyrosine D radical (YD
•) of photosystem II (PSII) in order to examine its relaxation enhancement by the oxygen-evolving complex (OEC) poised to the
reduced S−1 and S−2 oxidation states by NO treatment. Analysis of the power saturation curves showed that the S−1 oxidation state of the OEC does not enhance the relaxation of YD
•: it therefore possesses a diamagnetic ground state. In contrast, the Mn(II)-Mn(III) multiline electron paramagnetic resonance
(EPR) signal characteristic of the S−2 oxidation state of the OEC was shown to provide a relaxation enhancement pathway for YD
•, however less efficient relative to the one provided by the S2-state multiline EPR signal. We also examined the YD
• relaxation enhancement characteristics of the EPR-silent oxidation state produced after brief (1–5 min) dark incubation at
0°C of a PSII sample poised to the EPRactive S−2 state. This EPR-silent oxidation state denoted as “0°C incubation” state was shown to possess remarkably similar P1/2 values with the EPR-active S−2 state in the overall examined temperature range (6–20 K). In addition, these values remained unchanged after successive cycles
of the OEC between the EPR-active S−2 state and the “0°C incubation” state. The data presented in this work point to the conclusion that the “0°C incubation” state
is indeed an S−2 oxidation state with half-integer spin. 相似文献
6.
V. A. Vodeneev E. K. Akinchits L. A. Orlova V. S. Sukhov 《Russian Journal of Plant Physiology》2011,58(6):974-981
The contributions of Ca2+, H+, and Cl− in generation of variation potentials (VP) in 3- to 4-week-old pumpkin (Cucurbita pepo L., cv. Mozoleevskaya) plants were assessed. During VP generation, transient alkalinization of the medium around the stem
was recorded with a potentiometric method. The pH changes were kinetically similar to the electric potential changes and were
apparently due to temporal suppression of the plasma-membrane electrogenic H+ pump. These data and the observed inhibition of VP in the stem zone treated locally with a metabolic inhibitor (NaN3) indicate that the VP generation is related to the reversible suppression of the H+-pump. The anion channel blocker (ethacrynic acid) decelerated significantly the front slope of VP and reduced the VP amplitude.
A short-term increase in external Cl− concentration around the stem was observed during potential transients representing the VP front slope and the pulses integrated
into VP. The removal of Ca2+ from extracellular medium inhibited the VP generation. It is proposed that Ca2+ plays a role in activation of anion channels and in the H+-pump inactivation. The VP generation is probably determined by a complex mechanism, with contributions from passive ion fluxes
(Ca2+, Cl−) moving along the electrochemical gradients and from changes in the electrogenic pump activity. 相似文献
7.
A confined aquifer in the Malm Karst of the Franconian Alb, South Germany was investigated in order to understand the role of the vadose zone in denitrifiaction processes. The concentrations of chemical tracers Sr2+ and Cl– and concentrations of stable isotope 18O were measured in spring water and precipitation during storm events. Based on these measurements a conceptual model for runoff was constructed. The results indicate that pre-event water, already stored in the system at the beginning of the event, flows downslope on vertical and lateral preferential flow paths. Chemical tracers used in a mixing model for hydrograph separation have shown that the pre-event water contribution is up to 30%. Applying this information to a conceptual runoff generation model, the values of 15N and 18O in nitrate could be calculated. Field observations showed the occurence of significant microbial denitrification processes above the soil/bedrock interface before nitrate percolates through to the deeper horizon of the vadose zone. The source of nitrate could be determined and denitrification processes were calculated. Assuming that the nitrate reduction follows a Rayleigh process one could approximate a nitrate input concentration of about 170 mg/l and a residual nitrate concentration of only about 15%. The results of the chemical and isotopic tracers postulate fertilizers as nitrate source with some influence of atmospheric nitrate. The combined application of hydrograph separation and determination of isotope values in 15N and 18O of nitrate lead to an improved understanding of microbial processes (nitrification, denitrification) in dynamic systems. 相似文献
8.
In two mountain ecosystems at the Alptal research site in central Switzerland, pulses of 15NO3 and 15NH4 were separately applied to trace deposited inorganic N. One forested and one litter meadow catchment, each approximately
1600 m2, were delimited by trenches in the Gleysols. K15NO3 was applied weekly or fortnightly over one year with a backpack sprayer, thus labelling the atmospheric nitrate deposition.
After the sampling and a one-year break, 15NH4Cl was applied as a second one-year pulse, followed by a second sampling campaign. Trees (needles, branches and bole wood),
ground vegetation, litter layer and soil (LF, A and B horizon) were sampled at the end of each labelling period. Extractable
inorganic N, microbial N, and immobilised soil N were analysed in the LF and A horizons. During the whole labelling period,
the runoff water was sampled as well. Most of the added tracer remained in both ecosystems. More NO3− than NH4+ tracer was retained, especially in the forest. The highest recovery was in the soil, mainly in the organic horizon, and in
the ground vegetation, especially in the mosses. Event-based runoff analyses showed an immediate response of 15NO3− in runoff, with sharp 15N peaks corresponding to discharge peaks. NO3− leaching showed a clear seasonal pattern, being highest in spring during snowmelt. The high capacity of N retention in these
ecosystems leads to the assumption that deposited N accumulates in the soil organic matter, causing a progressive decline
of its C:N ratio. 相似文献
9.
The molecular weight and subunit composition of Cl-,HCO3(-)- and picrotoxin-stimulated Mg2+-ATPase from rat brain plasma membrane solubilized in sodium deoxycholate were studied by gel filtration chromatography. The enzyme activity eluted from a Sephacryl S-300 column in a single peak associated with a protein of molecular weight approximately 300 kD and a Stokes radius of 5.4 nm. The enzyme-enriched fraction, concentrated and denatured by SDS, migrated through a Sephacryl S-200 column as three peaks with molecular weights of approximately 57, 53, and 45 kD. SDS-PAGE also showed three major protein bands with molecular weights of about 57, 53, and 48 kD. The molecular weight and subunit composition of the Cl- and HCO3(-)-stimulated Mg2+-ATPase from neuronal membrane of rat brain are similar with the molecular properties of GABA(A)-benzodiazepine receptor complex from mammalian brain but are different from those of P-type transport ATPases. 相似文献
10.
V. A. Belyaev M. M. Dubrovin D. A. Kozlov A. A. Terent’ev A. E. Trenin G. V. Sholin 《Plasma Physics Reports》2010,36(11):964-968
D2− ions produced in collisions of D− ions with relative energies of 2.5–9.2 eV were detected for the first time. It is shown that the effective cross section
for this reaction is no less than 1.5 × 10−14 cm2. Along with the theoretically predicted short-lived state of negative molecular deuterium ions, a state existing for more
than 1 μs was observed. 相似文献
11.
Massive anthropogenic acceleration of the global nitrogen (N) cycle has stimulated interest in understanding the fate of excess
N loading to aquatic ecosystems. Nitrate (NO3
−) is traditionally thought to be removed mainly by microbial respiratory denitrification coupled to carbon (C) oxidation,
or through biomass assimilation. Alternatively, chemolithoautotrophic bacterial metabolism may remove NO3
− by coupling its reduction with the oxidation of sulfide to sulfate (SO4
2−). The NO3
− may be reduced to N2 or to NH4
+, a form of dissimilatory nitrate reduction to ammonium (DNRA). The objectives of this study were to investigate the importance
of S oxidation as a NO3
− removal process across diverse freshwater streams, lakes, and wetlands in southwestern Michigan (USA). Simultaneous NO3
− removal and SO4
2− production were observed in situ using modified “push-pull” methods in nine streams, nine wetlands, and three lakes. The
measured SO4
2− production can account for a significant fraction (25–40%) of the overall NO3
− removal. Addition of 15NO3
− and measurement of 15NH4
+ production using the push–pull method revealed that DNRA was a potentially important process of NO3
− removal, particularly in wetland sediments. Enrichment cultures suggest that Thiomicrospira denitrificans may be one of the organisms responsible for this metabolism. These results indicate that NO3
−-driven SO4
2− production could be widespread and biogeochemically important in freshwater sediments. Removal of NO3
− by DNRA may not ameliorate problems such as eutrophication because the N remains bio-available. Additionally, if sulfur (S)
pollution enhances NO3
− removal in freshwaters, then controls on N processing in landscapes subject to S and N pollution are more complex than previously
appreciated.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
S. A. Menzikov O. V. Menzikova 《Journal of Evolutionary Biochemistry and Physiology》2007,43(3):295-304
Action of Cl? + HCO3 ?1 ions on Mg2+-ATPase from brain plasma membranes of fish and rats has been studied. Maximal effect of the anions on the “basal” Mg2+-ATPase activity is revealed in the presence of 10 mM Cl? and 3 mM HCO3 ?1 at physiological values of pH of incubation medium. The studied Cl?, HCO3 ?-activated Mg2+-ATPases of both animal species, by their sensitivity to SH-reagents (5,5-dithio-bis-nitrobenzoic acid, N-ethylmaleimide), oligomycin, and orthovanadate, are similar to transport ATPase of the P-type, but differ from them by molecular properties and by sensitivity to ligands of GABAA-receptors. It has been established that the sensitive to GABAA-ergic ligands, Cl?, HCO3 ?-activated Mg2+-ATPase from brain of the both animal species is protein of molecular mass around 300 kDa and of Stock’s radius 5.4 nm. In fish the enzyme is composed of one major unit of molecular mass approximately 56 kDa, while in rats-of three subunits of molecular masses about 57, 53, and 45 kDa. A functional and structural coupling of the ATP-hydrolyzing areas of the studied enzyme to sites of binding of GABAA-receptor ligands is suggested. 相似文献
13.
Qingming Wang Huifang Sun Weilin Sha Juan Chen Liuyue Gu Dong Wang Xinhui Tang 《Biometals》2017,30(3):441-447
A novel S2O3 2? luminescent sensor (Cu2+-p-CPIP) was developed and the presence of S2O3 2? caused an obvious fluorescence enhancement at 420 nm upon excitation at 330 nm, which could be distinguished with the naked eye under a UV lamp. Remarkably, the compound exhibited excellent selective and sensitive response to S2O3 2? over other common anions with a micromolar limit of detection (0.442 μM) in DMSO/H2O (v/v, 1:1) buffer. The absorbance intensity and the color of Cu2+-p -CPIP solution changed gradually with the increase of S2O3 2? concentration. The proposed method was applied to the determination of S2O3 2? in milk samples and the recoveries were 97.5–105%. The preparation of Cu2+-p -CPIP exhibited the quick, simple and facile advantages. The results showed that Cu2+-p -CPIP can be a good candidate for simple, rapid and sensitive colorimetric detection of S2O3 2? in aqueous solution. 相似文献
14.
The cystine/glutamate exchanger (antiporter xc−) is a membrane transporter involved in the uptake of cystine, the rate-limiting amino acid in the synthesis of glutathione.
Recent studies suggest that the antiporter plays a role in the slow oxidative excitotoxity and in the pathological effects
of β-N-oxalylamino-l-alanine, the molecule responsible for neurolathyrism, a neurotoxic upper motor neuron disease. The mouse cystine/glutamate
exchanger has been cloned and showed to be composed of two distinct proteins, one of which being a novel protein, named xCT,
of 502 amino acids and 12 putative trans-membrane domains. We have generated and purified a polyclonal antibody to mouse xCT
and studied its expression in rat brain and in different cultured cells (astrocytes, fibroblasts and neurons) using Western
blot and immunocytochemical techniques. Expression of xCT was also studied in rat brain and muscle at different developmental
stages. Parallel experiments were carried out with antibodies to the heavy chain of 4F2 surface antigen, the non-specific
subunit of the antiporter xc−. xCT antibody detected in all cell and tissue extracts a specific band of about 40 kDa. Subcellular fractionation demonstrated
that xCT is concentrated mainly in the microsomal-mitochondrial fraction, in accord with its structure as transmembrane protein.
Immunocytochemical analysis showed a strong staining in all cells examined, included neurons. Furthermore, both xCT and the
heavy chain of 4F2 surface antigen increased in the brain during development, reaching the highest expression in adulthood.
The study of the expression and developmental profile of xCT represents a first step towards a better characterization of
its biochemical properties and function, which in turn may help to understand the relative contribution of the xc− antiporter in the pathogenesis of certain neurodegenerative diseases. 相似文献
15.
Torres ML Ortega F Cuaranta I González J Sanchez-Armass S 《Neurochemical research》2008,33(8):1574-1581
The Na+/H+ exchanger has been the only unequivocally demonstrated H+-transport mechanism in the synaptosomal preparation. We had previously suggested that a Cl−–H+ symporter (in its acidifying mode) is involved in cytosolic pH regulation in the synaptosomal preparation. Supporting this
suggestion, we now show that: (1) when synaptosomes are transferred from PSS to either gluconate or sulfate solutions, the
Fura-2 ratio remains stable instead of increasing as it does in 50 mM K solution. This indicates that these anions do not
promote a plasma membrane depolarization. (2) Based in the recovery rate from the cytosolic alkalinization, the anionic selectivity
of the Cl−–H+ symporter is NO3− > Br− > Cl− >> I− = isethionate = sulfate = methanesulfonate = gluconate. (3) PCMB 10 μM inhibits the gluconate-dependent alkalinization by
30 ± 6%. (4) Neither Niflumic acid, 9AC, Bumetanide nor CCCP inhibits the recovery from the cytosolic alkalinization.
Special issue article in honor of Dr. Ricardo Tapia. 相似文献
16.
Ab initio (RHF, MP2) and Density Functional Theory (DFT) methods have been used to examine six isomers of the N15m cluster with the 6-31+G* basis set. Different from the known odd-numbered anionic N7m, N9m, and N11m clusters, in which the open-chain structures are the most stable species, the most stable N15m isomer is structure 1 (C1), which may be considered as a complex between the fragments cyclic N5m (D5h) and staggered N10 (D2d). The decomposition pathways of structure 2 (CS), containing two aromatic N5 rings connected by a N5 chain, and the open-chain structure 3 (C2v) were studied at the B3LYP/6-31+G* level of theory. Relative energies were refined at the level of B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G*+ZPE (B3LYP/6-31+G*). The barriers for N2 and N5m (D5h) fission reactions for structure 2 are predicted to be 18.2 and 14.2 kcal x mol(-1), respectively. The corresponding N2+N3m fission barrier for structure 3 is predicted to be 11.2 kcal x mol(-1). Supplementary material is available for this article if you access the article at http://dx.doi.org/10.1007/s00894-003-0118-0. A link in the frame on the left on that page takes you directly to the supplementary material. Figure Structure 1 of the N15m cluster, showing bond distances in A and bond angles in degrees 相似文献
17.
Gabriel Arrambide Daniel A. Barrio Susana B. Etcheverry Dinorah Gambino Enrique J. Baran 《Biological trace element research》2010,136(2):241-248
The dihydrated potassium salt of the complex anion [VO(O2)NTA]2− (NTA = nitrilotriacetate anion, [N(CH2-COO)3]3−) was thoroughly characterized by electronic and vibrational (infrared and Raman) spectroscopies. The bioactivity of the complex
on the cell proliferation was tested on three cell lines in culture (UMR106 rat osteosarcoma-derived cells, Caco-2 derived
from a human colon adenocarcinoma, and RAW 264.7, a macrophage murine cell line). 相似文献
18.
The kinetics of rose bengal-sensitized photooxidation of tyrosine and several tyrosine-derivatives (tyr-D) named tyrosine methyl ester, tyrosine ethyl ester and tyrosine benzyl ester was studied in buffered pH 11 water, and buffered pH 11 micellar aqueous solutions of 0.01 M cetyltrimethylammonium chloride (CTAC) and 0.01 M-octylphenoxypolyethoxyethanol [triton X100 (TX100)]. Through time-resolved phosphorescence detection of singlet molecular oxygen (O(2)((1)Delta(g))) and polarographic determination of oxygen consumption, the respective bimolecular rate constants for reactive (k(r)) and overall (k(t)) quenching of the oxidative species by tyr-D were evaluated. Both rate constants behave in different fashion depending on the particular reaction medium. k(r)/k(t) values, increase in the sense CTAC相似文献
19.
20.
Lumenal extrinsic proteins PsbO, PsbP, and PsbQ of photosystem II (PSII) protect the catalytic cluster Mn4CaO5 of oxygen-evolving complex (OEC) from the bulk solution and from soluble compounds in the surrounding medium. Extraction of PsbP and PsbQ proteins by NaCl-washing together with chelator EGTA is followed also by the depletion of Ca2+ cation from OEC. In this study, the effects of PsbP and PsbQ proteins, as well as Ca2+ extraction from OEC on the kinetics of the reduced primary electron acceptor (QA ?) oxidation, have been studied by fluorescence decay kinetics measurements in PSII membrane fragments. We found that in addition to the impairment of OEC, removal of PsbP and PsbQ significantly slows the rate of electron transfer from QA ? to the secondary quinone acceptor QB. Electron transfer from QA ? to QB in photosystem II membranes with an occupied QB site was slowed down by a factor of 8. However, addition of EGTA or CaCl2 to NaCl-washed PSII did not change the kinetics of fluorescence decay. Moreover, the kinetics of QA ? oxidation by QB in Ca-depleted PSII membranes obtained by treatment with citrate buffer at pH 3.0 (such treatment keeps all extrinsic proteins in PSII but extracts Ca2+ from OEC) was not changed. The results obtained indicate that the effect of NaCl-washing on the QA ? to QB electron transport is due to PsbP and PsbQ extrinsic proteins extraction, but not due to Ca2+ depletion. 相似文献