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1.
Fluorescent proteins show fluorescence quenching by specific metal ions, which can be applied towards metal biosensing applications. In order to develop metal-biosensor, we performed spectroscopic analysis of the fluorescence quenching of fluorescent protein AmCyan and mOrange2 by various metal ions. The fluorescence intensity of AmCyan was reduced to 48.54% by Co2+ and 67.77% by Zn2+; Cu2+ reduced the fluorescence emission of AmCyan to 19.30% of its maximum. The fluorescence intensity of mOrange2 was quenched by only Cu2+, to 11.48% of its maximum. When analyzed by Langmuir equation, dissociation constants for AmCyan and mOrange2 were 56.10 and 21.46 µM, respectively. The Cu2+ quenching of AmCyan and mOrange2 were reversible upon treatment with the metal chelator EDTA, indicating that the metal ions were located on the protein surface. Their model structures suggest that AmCyan and mOrange2 have novel metal-binding sites. 相似文献
2.
I. Yu. Petrushanko V. A. Mitkevich V. A. Borzova S. S. Yakushev O. D. Lopina A. A. Makarov 《Biophysics》2009,54(6):686-690
The Na+/K+-ATPase generates an electrochemical gradient of Na+ and K+, which is necessary for the functioning of animal cells. During the catalytic act, the enzyme passes through two principal
conformational states, E1 and E2. To assess the domain organization of the protein in these conformations, thermal denaturation of Na+/K+-ATPases from duck salt gland and from rabbit kidney has been studied in the absence and in the presence of Na+ or K+, which induce the transition to E1 or E2. The melting curves for the ion-free forms of the two ATPases have different shapes: the rabbit protein shows one transition
at 56.1°C, whereas the duck protein shows two transitions, at 49.8 and 56.9°C. Addition of Na+ or K+ ions abolishes the difference in thermal behavior between these enzymes, but through opposite effects. The melting curves
for the E2 conformation (K+ bound) in both cases exhibit a single peak of heat absorption at ∼63°C. For the E1 conformation (Na+ bound), each melting curve has three peaks, indicating denaturation of three domains. The difference in the domain organization
of Na+/K+-ATPase in the E1 and E2 states may account for the different sensitivity to temperature, proteolysis, and oxidative stress
observed for the two enzyme conformations. 相似文献
3.
Hlima HB Aghajari N Ali MB Haser R Bejar S 《Journal of industrial microbiology & biotechnology》2012,39(4):537-546
The role of two amino acid residues linked to the two catalytic histidines His54 and His220 in kinetics and physicochemical
properties of the Streptomyces sp. SK glucose isomerase (SKGI) was investigated by site-directed mutagenesis and molecular modeling. Two single mutations,
F53L and G219D, and a double mutation F53L/G219D was introduced into the xylA SKGI gene. The F53L mutation increases the thermostability and the catalytic efficiency and also slightly shifts the optimum
pH from 6.5 to 7, but displays a profile being similar to that of the wild-type enzyme concerning the effect of various metal
ions. The G219D mutant is resistant to calcium inhibition retaining about 80% of its residual activity in 10 mM Ca2+ instead of 10% for the wild-type. This variant is activated by Mn2+ ions, but not Co2+, as seen for the wild-type enzyme. It does not require the latter for its thermostability, but has its half-life time displaced
from 50 to 20 min at 85°C. The double mutation F53L/G219D restores the thermostability as seen for the wild-type enzyme while
maintaining the resistance to the calcium inhibition. Molecular modeling suggests that the increase in thermostability is
due to new hydrophobic interactions stabilizing α2 helix and that the resistance to calcium inhibition is a result of narrowing
the binding site of catalytic ion. 相似文献
4.
A two-stage technology for bacterial and chemical leaching of nonferrous metals in a specifically designed laboratory unit has been proposed. At the first stage of leaching, ferric iron formed during the second stage of oxidation of Fe2+ ions by mesophilic chemolithotrophic microorganisms was used. The optimal parameters of the first stage of the process (flow rate, temperature, and the process duration) were 2 l/h, 75°C, and 24 h, respectively. The results of testing of the two-stage technology for leaching copper-zinc raw materials indicated that the depth of zinc and copper leaching can be increased from 70 to 93% and from 40 to 58.8%, respectively, and the process duration can be reduced from 120 to 24 h as compared to the commonly used one-stage technology. 相似文献
5.
It was shown that La3+ induced aggregation of plant protoplasts. Incubation of a suspension of aggregated protoplasts at 42°C for 30 min resulted
in protoplast fusion. 相似文献
6.
C. Derrick QuarlesJr. R. Kenneth Marcus Julia L. Brumaghim 《Journal of biological inorganic chemistry》2011,16(6):913-921
Competitive binding of Fe3+, Cr3+, and Ni2+ to transferrin (Tf) was investigated at various physiological iron to Tf concentration ratios. Loading percentages for these
metal ions are based on a two M
n+ to one Tf (i.e., 100% loading) stoichiometry and were determined using a particle beam/hollow cathode–optical emission spectroscopy
(PB/HC-OES) method. Serum iron concentrations typically found in normal, iron-deficient, iron-deficient from chronic disease,
iron-deficient from inflammation, and iron-overload conditions were used to determine the effects of iron concentration on
iron loading into Tf. The PB/HC-OES method allows the monitoring of metal ions in competition with Fe3+ for Tf binding. Iron-overload concentrations impeded the ability of chromium (15.0 μM) or nickel (10.3 μM) to load completely
into Tf. Low Fe3+ uptake by Tf under iron-deficient or chronic disease iron concentrations limited Ni2+ loading into Tf. Competitive binding kinetic studies were performed with Fe3+, Cr3+, and Ni2+ to determine percentages of metal ion uptake into Tf as a function of time. The initial rates of Fe3+ loading increased in the presence of nickel or chromium, with maximal Fe3+ loading into Tf in all cases reaching approximately 24%. Addition of Cr3+ to 50% preloaded Fe3+–Tf showed that excess chromium (15.0 μM) displaced roughly 13% of Fe3+ from Tf, resulting in 7.6 ± 1.3% Cr3+ loading of Tf. The PB/HC-OES method provides the ability to monitor multiple metal ions competing for Tf binding and will
help to understand metal competition for Tf binding. 相似文献
7.
Anil Boda Sk. Musharaf Ali Madhav R. K. Shenoi Hanmanth Rao Sandip K. Ghosh 《Journal of molecular modeling》2011,17(5):1091-1108
Crown ether architectures were explored for the inclusion of Cs+ and Sr2+ ions within nano-cavity of macrocyclic crown ethers using density functional theory (DFT) modeling. The modeling was undertaken
to gain insight into the mechanism of the complexation of Cs+ and Sr2+ ion with this ligand experimentally. The selectivity of Cs+ and Sr2+ ions for a particular size of crown ether has been explained based on the fitting and binding interaction of the guest ions
in the narrow cavity of crown ethers. Although, Di-Benzo-18-Crown-6 (DB18C6) and Di-Benzo-21-Crown-7 (DB21C7) provide suitable
host architecture for Sr2+ and Cs+ ions respectively as the ion size match with the cavity of the host, but consideration of binding interaction along with
the cavity matching both DB18C6 and DB21C7 prefers Sr2+ ion. The calculated values of binding enthalpy of Cs metal ion with the crown ethers were found to be in good agreement with
the experimental results. The gas phase binding enthalpy for Sr2+ ion with crown ether was higher than Cs metal ion. The ion exchange reaction between Sr and Cs always favors the selection
of Sr metal ion both in the gas and in micro-solvated systems. The gas phase selectivity remains unchanged in micro-solvated
phase. We have demonstrated the effect of micro-solvation on the binding interaction between the metal ions (Cs+ and Sr2+) and the macrocyclic crown ethers by considering micro-solvated metal ions up to eight water molecules directly attached
to the metal ion and also by considering two water molecules attached to metal-ion-crown ether complexes. A metal ion exchange
reaction involving the replacement of strontium ion in metal ion-crown ether complexes with cesium ion contained within a
metal ion-water cluster serves as the basis for modeling binding preferences in solution. The calculated O-H stretching frequency
of H2O molecule in micro-solvated metal ion-crown complexes is more red-shifted in comparison to hydrated metal ions. The calculated
IR spectra can be compared with an experimental spectrum to determine the presence of micro-solvated metal ion–crown ether
complexes in extractant phase. 相似文献
8.
Martin Pipíška Miroslav Horník L’uboš Vrtoch Jozef Augustín Juraj Lesný 《Biologia》2007,62(3):276-282
Cobalt is one of the possible contaminants originating from radioactive wastes or from metal mines and refineries. This paper
describes sorption of cobalt by the foliose lichen Hypogymnia physodes from CoCl2 solutions spiked with 60Co2+ in laboratory experiments. Maximum uptake was reached within 1 hour; the biosorption after 24 hours is not pH-dependent within
the range of pH 4–7, negligible at pH 2 and is not dependent on metabolic activity. The process can be described by the Freundlich
adsorption isotherm with ln k = 2.77, 1/n = 0.22 and R
2 = 0.94. Bivalent metal ions showed a concentration-dependent competitive effect on cobalt biosorption, decreasing in the
order: Cu > Ni > Ca > Mg. Monovalent ions, such as K+ and Na+, showed only very weak competitive effect. Up to 98% of Co taken up by lichen can be removed by washing with 0.1 M NiCl2 at 20°C. This means that only a small fraction of the cobalt is localized intracellularly. These results can be used for
elucidating the behaviour of lichens as bioindicators of cobalt pollution in water systems, including the risk of cobalt leakage
from lichen probes under the influence of rain, snow and atmospheric humidity. 相似文献
9.
Aerobic granulation is a promising technology for wastewater treatment, but problems regarding its formation and stability need to be solved. Divalent metal ions, especially Ca2+, Mg2+ and Mn2+, have been demonstrated to play an important role in the process of aerobic granulation. Here, we studied whether iron ions can affect aerobic granulation. Granular sludge formed without iron ion addition (<0.02 mg Fe2+ L?1) was fluffy and had a finger-type structure and filamentous out-growth. The addition of iron ions to concentrations of 1 and 10 mg Fe2+ L?1 repressed the finger-type structure and filamentous out-growth. The results show that chemical precipitation in the granules with iron ion addition was higher than that in the granules without ferrous addition. The amount of precipitates was higher inside the granules than outside. This study demonstrates that iron ions (Fe2+/Fe3+) increase the size and stability of aerobic granular sludge but do not affect the granulation time, which is the time that the first granular sludge is observed. The study shows that aerobic granular sludge technology can be confidently applied to actual wastewater containing a high concentration of iron compounds. 相似文献
10.
Alexandre C. Bertoli Jerusa S. Garcia Marcello G. Trevisan Teodorico C. Ramalho Matheus P. Freitas 《Biometals》2016,29(2):275-285
The use of theoretical calculation to determine structural properties of fulvate-metal complex (zinc, copper and iron) is here related. The species were proposed in the ratio 1:1 and 2:1 for which the molecular structure was obtained through the semi-empirical method PM6. The calculation of thermodynamic stability (\(\Delta H_{(aq.)}^{0}\)) predicted that the iron complex were more exo-energetic. Metallic ions were coordinated to the phtalate groups of the model-structure of fulvic acid Suwannee River and the calculations of vibrational frequencies suggested that hydrogen bonds may help on the stability of the complex formation. 相似文献
11.
12.
Qi Jing Yu Qing Shan Zhou Hai Bo Huang Yan Lin Wan Shu Fang Tian Dai Ming Duan 《Neurochemical research》2009,34(12):2192-2196
To test the effects of ketamine on metal ion balance in the spinal cord tissues after ischemic reperfusion (I/R), 24 white
adult Japanese rabbits were randomly assigned to sham operation group, I/R group or ketamine-treated I/R group. Spinal cord
injuries in I/R group and ketamine-treated I/R group were induced by aortic occlusions. Rabbits in ketamine-treated I/R group
were intravenously infused 10 mg/kg ketamine twice: once at 10 min before aortic clamping and once at the onset of reperfusion.
Post-operative neurological functions and concentrations of ions Ca2+, Mg2+, Cu2+ and Zn2+ in the spinal cord were assessed. Compared with the sham operation group, rabbits in the I/R group showed significantly worsened
neurological functions as scored with the modified Tarlov criteria and altered concentrations of ions Ca2+, Mg2+, Cu2+ and Zn2+. These unfavorable changes were significantly reversed in the ketamine-treated I/R group, suggesting that the potent protective
effects of ketamine against the I/R-induced spinal cord injuries may be due to its ability to maintain ion balance in the
I/R affected tissues. 相似文献
13.
Berezin I Mizrachy-Dagry T Brook E Mizrahi K Elazar M Zhuo S Saul-Tcherkas V Shaul O 《Plant cell reports》2008,27(5):939-949
AtMHX is a vacuolar transporter encoded by a single gene in Arabidopsis. Electrophysiological analysis showed that it exchanges protons with Mg2+, Zn2+, and Fe2+ ions. The physiological impact of AtMHX was examined so far only in tissue-culture grown seedlings of tobacco plants overexpressing
this transporter. Here we investigated the impact of AtMHX on growth, response to different metals, and metal accumulation
of mature tobacco plants, as well as Arabidopsis plants in which we overexpressed this transporter. The analyses were carried out in hydroponic growth-systems, in which the
mineral composition could be effectively controlled, and the metal content of roots could be examined. Transformed tobacco
plants showed necrotic lesions and apical burnings upon growth with increased levels of Mg2+, Zn2+, and Cd2+ ions. This suggested that AtMHX can carry in planta not only Mg2+ and Zn2+ ions, as previously deduced based on observations in tissue-culture, but also Cd2+ ions. Transformed plants of both tobacco and Arabidopsis showed a reduction in plant size. However, the overall response of Arabidopsis to AtMHX overexpression was minor. No change was detected in the mineral content of any organ of the transgenic tobacco or
Arabidopsis plants. The necrotic lesions in tobacco resembled those seen in plants with perturbed proton balancing, raising the assumption
that AtMHX can affect the proton homeostasis of cells. In agreement with this assumption, the transformed tobacco plants had
increased expression and activity of the vacuolar H+-ATPase. The relative significance of AtMHX for metal and proton homeostasis still has to be elucidated. 相似文献
14.
Removal of heavy metals (Pb2+, Zn2+) from aqueous solution by dried biomass of Spirulina sp. was investigated. Spirulina rapidly adsorbed appreciable amount of lead and zinc from the aqueous solutions within 15 min of initial contact with the
metal solution and exhibited high sequestration of lead and zinc at low equilibrium concentrations. The specific adsorption
of both Pb2+ and Zn2+ increased at low concentration and decreased when biomass concentration exceeded 0.1 g l−1. The binding of lead followed Freundlich model of kinetics where as zinc supported Langmuir isotherm for adsorption with
their r
2
values of 0.9659 and 0.8723 respectively. The adsorption was strongly pH dependent as the maximum lead biosorption occurred
at pH 4 and 10 whereas Zn2+ adsorption was at pH 8 and 10. 相似文献
15.
Isocitrate dehydrogenase kinase/phosphatase (AceK) is a bifunctional enzyme with both kinase and phosphatase activities that are activated by Mg2+. We have studied the interactions of Mn2+and Mg2+ with AceK using isothermal titration calorimetry (ITC) combined with molecular docking simulations and show for the first time that Mn2+ also activates the enzyme activities. However, Mn2+ and Mg2+ exert their effects by different mechanisms. Although they have similar binding constants (of 1.11?×?105 and 0.98?×?105 M?1, respectively) for AceK and induce conformational changes of the enzyme, they do not compete for the same binding site. Instead Mn2+ appears to bind to the regulatory domain of AceK, and its effect is transmitted to the active site of the enzyme by the conformational change that it induces. The information in this study should be very useful for understanding the molecular mechanism underlying the interaction between AceK and metal ions, especially Mn2+ and Mg2+. 相似文献
16.
Derek R. Laver 《Biophysical reviews》2018,10(4):1087-1095
Ryanodine receptors (RyRs) are the Ca2+ release channels in the sarcoplasmic reticulum in striated muscle which play an important role in excitation-contraction coupling and cardiac pacemaking. Single channel recordings have revealed a wealth of information about ligand regulation of RyRs from mammalian skeletal and cardiac muscle (RyR1 and RyR2, respectively). RyR subunit has a Ca2+ activation site located in the luminal and cytoplasmic domains of the RyR. These sites synergistically feed into a common gating mechanism for channel activation by luminal and cytoplasmic Ca2+. RyRs also possess two inhibitory sites in their cytoplasmic domains with Ca2+ affinities of the order of 1 μM and 1 mM. Magnesium competes with Ca2+ at these sites to inhibit RyRs and this plays an important role in modulating their Ca2+-dependent activity in muscle. This review focuses on how these sites lead to RyR modulation by Ca2+ and Mg2+ and how these mechanisms control Ca2+ release in excitation-contraction coupling and cardiac pacemaking. 相似文献
17.
Cd2+ is highly toxic to Staphylococcus aureus since it blocks dithiols in cytoplasmic 2-oxoglutarate dehydrogenase complex (ODHC) participating in energy conservation process. However, S. aureus 17810R is Cd2+-resistant due to possession of cadA-coded Cd2+ efflux system, recognized here as P-type Cd2+-ATPase. This Cd2+ pump utilizing cellular energy—ATP, ?μ H + (electrochemical proton potential) and respiratory protons, extrudes Cd2+ from cytoplasm to protect dithiols in ODHC, but the mechanism of Cd2+ extrusion remains unknown. Here we propose that two Cd2+ taken up by strain 17810R via Mn2+ uniporter down membrane potential (?ψ) generated during glutamate oxidation in 100 mM phosphate buffer (high PiB) are trapped probably by high affinity sites in cytoplasmic domain of Cd2+-ATPase, forming SCdS. This stops Cd2+ transport towards dithiols in ODHC, allowing undisturbed NADH production, its oxidation and energy conservation, while ATP could change orientation of SCdS towards facing transmembrane channel. Now, increased number of Pi-dependent protons pumped electrogenically via respiratory chain and countertransported through the channel down ?ψ, extrude two trapped cytoplasmic Cd2+, which move to low affinity sites, being then extruded into extracellular space via ?ψ-dependent Cd2+/H+ exchange. In 1 mM phosphate buffer (low PiB), external Cd2+ competing with decreased number of Pi-dependent protons, binds to ψs of Cd2+-ATPase channel, enters cytoplasm through the channel down ?ψ via Cd2+/Cd2+ exchange and blocks dithiols in ODHC. However, Mg2+ pretreatment preventing external Cd2+ countertransport through the channel down ?ψ, allowed undisturbed NADH production, its oxidation and extrusion of two cytoplasmic Cd2+ via Cd2+/H+ exchange, despite low PiB. 相似文献
18.
Fezoua-Boubegtiten Z Desbat B Brisson A Gounou C Laguerre M Lecomte S 《European biophysics journal : EBJ》2011,40(5):641-649
Annexin A5 (AnxA5) binds to negatively charged phospholipid membranes in a Ca2+ dependent manner. Several studies already demonstrate that Mg2+ ions cannot induce the binding. In this paper, quartz crystal microbalance with dissipation monitoring (QCM-D), Brewster
angle microscopy (BAM), polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) and molecular dynamics
(MD) were performed to elucidate the high specificity of Ca2+ versus Mg2+ on AnxA5 binding to membrane models. In the presence of Ca2+, AnxA5 showed a strong interaction with lipids, the protein is adsorbed mainly in α-helix under the DMPS monolayer, with
an orientation of the α-helices axes slightly tilted with respect to the normal of the phospholipid monolayer as revealed
by PMIRRAS. The Ca2+ ions interact strongly with the phosphate group of the phospholipid monolayer. In the presence of Mg2+, instead of Ca2+, no interaction of AnxA5 with lipids was detected. Molecular dynamics simulations allow us to explain the high specificity
of calcium. Ca2+ ions are well exposed and surrounded by labile water molecules at the surface of the protein, which then favour their binding
to the phosphate group of the membrane, explaining their specificity. To the contrary, Mg2+ ions are embedded in the protein structure, with a smaller number of water molecules strongly bound. We conclude that the
embedded Mg2+ ions inside the AnxA5 structure are not able to link the protein to the phosphate group of the phospholipids for this reason. 相似文献
19.
Effect of the ions of heavy metals (copper, zinc, and nickel) on growth of and ferrous iron oxidation by extremely acidophilic archaeal strains of the genus Acidiplasma (Acidiplasma sp. MBA-1; A. aeolicum V1T; and A. cupricumulans BH2T) was studied. Effect of the metals depending on their concentration was studied within the range from 5 to 1000 mM. All studied strains were able to oxidize iron in the presence of the highest tested heavy metal concentrations (1000 mM). All metal ions had, however, a noticeable inhibitory effect both on both growth and on iron oxidation. The lowest concentrations of copper, zinc, and nickel partially suppressing microbial growth were determined (5, 10, and 5 mM, respectively). These findings are of interest, since almost no literature data on resistance of Acidiplasma archaea to heavy metals are available, although these prokaryotes are among the most important groups of microorganisms used in biohydrometallurgy. 相似文献
20.
Gang Tang Yi Shen Pan Gao Shuang-Shuang Song Liang-Yi Si 《In vitro cellular & developmental biology. Animal》2018,54(3):250-256
Cardiac hypertrophy plays a major role in heart failure and is related to patient morbidity and mortality. Calcium overloading is a main risk for cardiac hypertrophy, and Na+/K+-ATPase (NKA) has been found that it could not only regulate intracellular Na+ levels but also control the intracellular Ca2+ ([Ca2+]i) level through Na+/Ca2+-exchanger (NCX). Recent studies have reported that klotho could affect [Ca2+]i level. In this study, we aimed at exploring the role of klotho in improving isoproterenol-induced hypertrophic response of H9C2 cells. The H9C2 cells were randomly divided into control and isoproterenol (ISO) (10 μM) groups. Klotho protein (10 μg/ml) or NKAα2 siRNA was used to determine the changes in isoproterenol-induced hypertrophic response. The alterations of [Ca2+]i level were measured by spectrofluorometry. Our results showed that H9C2 cells which were treated with isoproterenol presented a higher level of [Ca2+]i and hypertrophic gene expression at 24 and 48 h compared with the control group. Moreover, the expressions of NKAα1 and NKAα2 were both increased in control and ISO groups after treating with klotho protein; meanwhile, the NKA activity was increased and NCX activity was decreased after treatment. Consistently, the [Ca2+]i level and hypertrophic gene expression were decreased in ISO group after klotho protein treatment. However, these effects were both prevented by transfecting with NKAα2 siRNA. In conclusion, these findings demonstrated that klotho inhibits isoproterenol-induced hypertrophic response in H9C2 cells by activating NKA and inhibiting the reverse mode of NCX and this effect may be associated with the upregulation of NKAα2 expression. 相似文献