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1.
Human arylamine N-acetyltransferase 1 (NAT1) is a xenobiotic-metabolizing enzyme that biotransforms aromatic amine chemicals. We show here that biologically-relevant concentrations of inorganic (Hg2+) and organic (CH3Hg+) mercury inhibit the biotransformation functions of NAT1. Both compounds react irreversibly with the active-site cysteine of NAT1 (half-maximal inhibitory concentration (IC50) = 250 nM and kinact = 1.4 × 104 M−1 s−1 for Hg2+ and IC50 = 1.4 μM and kinact = 2 × 102 M−1 s−1 for CH3Hg+). Exposure of lung epithelial cells led to the inhibition of cellular NAT1 (IC50 = 3 and 20 μM for Hg2+ and CH3Hg+, respectively). Our data suggest that exposure to mercury may affect the biotransformation of aromatic amines by NAT1.  相似文献   

2.
Adsorption of Hg2+ and methylmercury (MeHg) to multi-walled carbon nanotubes (MWCNTs) modified, respectively, with hydroxyl, amine and carboxyl groups was studied. The effect of various factors like the initial pH, natural organic matter (NOM), Cl- and adsorbent dose on the sorption efficiency were evaluated. It was found that amine-modified MWCNTs showed a strong adsorption capacity to Hg2+ and MeHg, and the removal efficiency could reach up to 92% (0.5 g/L MWCNTs, and 100 μg/L Hg2+ and MeHg) which is independent of pH. NOM had complex effects on the adsorption of Hg2+ and MeHg to MWCNTs. Cl- inhibited the adsorption of Hg2+ and MeHg to MWCNTs. The adsorption of Hg2+ and MeHg was found to be inhomogeneous and homogeneous chemisorption, respectively. Our results suggested that MWCNTs modified with different functional groups can efficiently adsorb both Hg2+ and MeHg in aqueous environment.  相似文献   

3.
Muscle glycogen phosphorylase (GP) plays an important role in muscle functions. Mercury has toxic effects in skeletal muscle leading to muscle weakness or cramps. However, the mechanisms underlying these toxic effects are poorly understood. We report that GP is irreversibly inhibited by inorganic (Hg2+) and organic (CH3Hg+) mercury (IC50 = 380 nM and kinact = 600 M−1 s−1 for Hg2+ and IC50 = 43 μM and kinact = 13 M−1 s−1 for CH3Hg+) through reaction of these compounds with cysteine residues of the enzyme. Our data suggest that the irreversible inhibition of GP could represent one of the mechanisms that contribute to mercury-dependent muscle toxicity.  相似文献   

4.
Eukaryotic algae were studied to determine their ability to biotransform HgII under aerated and pH controlled conditions. All algae converted HgII into β-HgS and Hg0 to varying degrees. When HgII was administered as HgCl2 to the algae, biotransformation by species of Chlorophyceae (Selenastrum minutum and Chlorella fusca var. fusca) was initiated with β-HgS synthesis (K 1/2 of hours) and concomitant Hg° evolution occurred in the first hour. Hg° synthesis was impeded by the formation of β-HgS and this inhibition was released in C. fusca var. fusca when cellular thiols were oxidized by the addition of dimethylfumarate (DMF). The diatom, Navicula pelliculosa (Bacillariophyceae), converted a substantially greater proportion of the applied HgII into Hg0, whereas the thermophilic alga, Galdieria sulphuraria (Cyanidiophyceae), rapidly biotransformed as much as 90% of applied HgII into β-HgS (K 1/2 ≈ 20 min). This thermophile was also able to generate Hg0 even after all exogenously applied HgCl2 had been biotransformed. The results suggest that β-HgS may be the major dietary mercurial for grazers of contaminated eukaryotic algae.  相似文献   

5.
Soil management practices that involve additions of organic materials may influence plant sulfur availability in highly-weathered, acid soils. This study evaluated the effects of organic additions on sulfate adsorption and sulfur availability in a limed (3,4 t ha-1) and unlimed Typic Haplustox soil of the Cerrado Region of Brazil. In unlimed soil, the proportion of applied sulfate (600 kg S ha-1 as gypsum) that was adsorbed temporarily decreased over two cropping seasons by incorporation of 10 t dry matter ha-1 crop-1 of guinea grass (Panicum maximum Jacq.) but not when a similar quantity of a tropical legume, feijâo de porco (Canavalia ensiformis L.), was added. Liming reduced sulfate adsorption and resulted in sulfate leaching to a depth of 30 to 45 cm. Both plant materials temporarily reduced sulfate adsorption in laboratory studies when added to an unlimed soil at a rate equivalent to 40 t ha-1. Analysis of soil properties affected by organic additions and liming showed significant correlations between sulfate adsorption and soil pH, extractable aluminum, calcium and magnesium, and surface charge. Maize dry matter yields increased by 1.3 to 3.5 t ha-1 with addition of both organic materials. However, only the feijâo de porco treatment resulted in increases in sulfur uptake for the years in which organic materials were applied. Determining the effects of organic material additions on plant sulfur availability is complicated by the combined effects of sulfur mineralization, sulfate adsorption, and the plant's ability to utilize adsorbed subsoil sulfate.Joint contribution of Cornell University and CPAC-EM- BRAPA. This research was supported by USAID through the Title XII CRSP subgrant SM-CRSP-10 from North Carolina State University  相似文献   

6.
Concentrations of methyl mercury, CH3Hg (II), total mercury, Hgtot = CH3Hg (II) + Hg (II), and organic sulphur species were determined in soils, soil solutions and streams of a small (50 ha) boreal forest catchment in northern Sweden. The CH3Hg (II)/Hgtot ratio decreased from 1.2–17.2% in the peaty stream bank soils to 0.4–0.8% in mineral and peat soils 20 m away from the streams, indicating that conditions for net methylation of Hg (II) are most favourable in the riparian zone close to streams. Concentrations of CH3Hg (II) bound in soil and in soil solution were significantly, positively correlated to the concentration of Hgtot in soil solution. This, and the fact that the CH3Hg (II)/Hgtot ratio was higher in soil solution than in soil may indicate that Hg (II) in soil solution is more available for methylation processes than soil bound Hg (II). Reduced organic S functional groups (Org-SRED) in soil, soil extract and in samples of organic substances from streams were quantified using S K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Org-SRED, likely representing RSH, RSSH, RSR and RSSR functionalities, made up 50 to 78% of total S in all samples examined. Inorganic sulphide [e.g. FeS2 (s)] was only detected in one soil sample out of 10, and in none of the stream samples. Model calculations showed that under oxic conditions nearly 100% of Hg (II) and CH3Hg (II) were complexed by thiol groups (RSH) in the soil, soil solution and in the stream water. Concentrations of free CH3Hg+ and Hg2+ ions in soil solution and stream were on the order of 10–18 and 10–32M, respectively, at pH 5. For CH3Hg (II), inorganic bi-sulphide complexes may contribute to an overall solubility at concentrations of inorganic sulphides higher than 10–9M, whereas considerably higher concentrations of inorganic sulphides (lower redox-potential) are required to increase the solubility of Hg (II).  相似文献   

7.
Mercury inputs and outputs at a small lake in northern Minnesota   总被引:1,自引:0,他引:1  
Storages and cycling of total mercury (HgT), methylmercury (MeHg), and Hg0 are described for Spring Lake, a small bog lake in the Marcell Experimental Forest in north-central Minnesota. We quantified photoredox transformations, MeHg photolysis, burial to the sediments, and internal and external loadings of HgT and MeHg. Atmospheric deposition was the main input of HgT; MeHg was supplied by a combination of atmospheric, near-shore wetland, and biotic (methylation) sources. HgT outputs were dominated by burial (67%), and Hg0 evasion accounted for 26% of HgT outputs. The watershed of Spring Lake is small (3.7× lake surface area), and accordingly, bog and upland runoff were minor contributors to both HgT and MeHg inputs. Wet deposition was ∼9% of total MeHg input, and other external inputs (runoff, sediment porewater) provided only an additional 7%, indicating that internal production of MeHg was occurring in the lake. Photolysis of MeHg, measured in the field and laboratory, removed ∼3× the lake mass of MeHg (20 mg) annually, and was the dominant sink for MeHg. Residence times of MeHg and HgT in the lake were 48 and 61 days, respectively, during the open-water season, compared with only 8 days for the residence time of MeHg on settling particles (seston). Photoreduction of Hg2+ to Hg0 was greater than the reverse reaction (Hg0 photooxidation), and the residence time of Hg0 in the photic zone was short (hours). Data from this study show active cycling of all the measured species of mercury (HgT, MeHg, and Hg0) and the importance of MeHg photolysis and photo-redox processes.  相似文献   

8.
In this study the husk of mango seed and two carbonaceous adsorbents prepared from it were used to study the adsorption behavior of eight acid dyes. The adsorbed amount in mmol m−2 decayed asymptotically as the molecular volume and area increased. The interaction between the studied dyes and the mesoporous carbon was governed by the ionic species in solution and the acidic/basic groups on the surface. Less than 50% of the external surface of the microporous carbon became covered with the dyes molecules, though monolayer formation demonstrating specific interactions only with active sites on the surface and the adsorption magnitudes correlated with the shape parameter of the molecule within a particular dye group. The adsorption behavior in mixtures was determined by the molecular volume of the constituents; the greater the molecular volume difference, the greater the effect on the adsorbed amount. We also demonstrated that the raw husk of the mango seed can be used to remove up to 50% from model 50 mg l−1 solutions of the studied acid dyes.  相似文献   

9.
In the present study a polystyrene microtiter plate was tested as a support material for synaptic plasma membrane (SPM) immobilization by adsorption. The adsorption was carried out by an 18-h incubation at +4°C of SPM with a polystyrene matrix, at pH 7.4. Evaluation of the efficiency of the applied immobilization method revealed that 10% protein fraction of initially applied SPM was bound to the support and that two SPM enzymes, Na+/K+-ATPase and Mg2+-ATPase, retained 70–80% activity after the adsorption. In addition, adsorption stabilizes Na+/K+-ATPase and Mg2+-ATPase, since the activities are substantial 3 weeks after the adsorption. Parallel kinetic analysis showed that adsorption does not alter significantly the kinetic properties of Na+/K+-ATPase and Mg2+-ATPase and their sensitivity to and mechanism of Cd2+- or Hg2+-induced inhibition. The only exception is the “high affinity” Mg2+-ATPase moiety, whose affinity for ATP and sensitivity toward Cd2+ were increased by the adsorption. The results show that such system may be used as a practical and comfortable model for the in vitro toxicological investigations.  相似文献   

10.
Heavy metal ion is one of the critical environmental pollutants accumulated in living organisms and causes toxic or carcinogenic effects once passed threshold levels. As an important member of Hsp70 (heat shock protein 70) family, the 78-kDa glucose-regulated protein (GRP78) can enhance cell survival rates remarkably under thermal stress. Recent studies also demonstrated that the expression of GRP78 enhances the cell survival under heavy metal stress. In this study, three most representative heavy metal ions, Pb2 +, Hg2 + and Cd2 +, were used to stimulate Ctenopharyngodon idella kidney (CIK) cells. The results showed that cell viability under Pb2 +, Hg2 + and Cd2 + stress decreased significantly. The longer and the greater the concentrations of stimulation from heavy metal ions, the higher the rate of cell death was observed. Among them, Hg2 + is the most hazardous to cells. Under the same stress condition, Hg2 + resulted in 50% of cell death, Cd2 + (or Pb2 +) led to 45% (or 35%) of cell death, respectively. Western immunoblotting indicated that C. idella GRP78 (CiGRP78) protein expression level was enhanced obviously in CIK cells under Pb2 +, Hg2 + and Cd2 + stress, meaning CiGRP78 is involved in heavy metal cytotoxicity. To further study the role of CiGRP78 in cytoprotection, we designed the siRNA against CiGRP78 (from nucleotides + 788 to + 806) and transfected it into CIK cells to silence endogenous CiGRP78. The viability rate of CIK cells transfected with or without siRNA incubated with HgCl2 for 12 h showed a significant decrease from 50% to 21%. Our results showed that CiGRP78 protects cells against heavy metal stimuli to some extent.  相似文献   

11.
The current review paper deals with critical evaluation of the thermodynamic parameters of adsorption equilibrium uptakes of heavy metals, dyes and other organic pollutants from the wastewater using low-cost adsorbents, activated carbon derived from agricultural waste, industrial wastes and other important adsorbent materials. Present review paper focus the spontaneity of adsorption processes when the thermodynamic parameters were assessed with the compensation effects of standard enthalpy change (ΔHo) and standard entropy change (ΔSo) with temperature. This paper also investigates the spontaneity of adsorption on the basis of thermodynamic criteria of spontaneity and the temperature range to predict feasibility of the adsorption processes.  相似文献   

12.
The enzyme mercuric ion reductase MerA is the central component of bacterial mercury resistance encoded by the mer operon. Many MerA proteins possess metallochaperone-like N-terminal domains (NmerA) that can transfer Hg2+ to the catalytic core domain (Core) for reduction to Hg0. These domains are tethered to the homodimeric Core by ∼ 30-residue linkers that are susceptible to proteolysis, the latter of which has prevented characterization of the interactions of NmerA and the Core in the full-length protein. Here, we report purification of homogeneous full-length MerA from the Tn21 mer operon using a fusion protein construct and combine small-angle X-ray scattering and small-angle neutron scattering with molecular dynamics simulation to characterize the structures of full-length wild-type and mutant MerA proteins that mimic the system before and during handoff of Hg2+ from NmerA to the Core. The radii of gyration, distance distribution functions, and Kratky plots derived from the small-angle X-ray scattering data are consistent with full-length MerA adopting elongated conformations as a result of flexibility in the linkers to the NmerA domains. The scattering profiles are best reproduced using an ensemble of linker conformations. This flexible attachment of NmerA may facilitate fast and efficient removal of Hg2+ from diverse protein substrates. Using a specific mutant of MerA allowed the formation of a metal-mediated interaction between NmerA and the Core and the determination of the position and relative orientation of NmerA to the Core during Hg2+ handoff.  相似文献   

13.
The accumulation of total mercury (HgT) andmethylmercury (MeHg) was evaluated in sediments ofTivoli South Bay, a freshwater tidal mudflat wetlandin the Hudson River National Estuarine ResearchReserve system. HgT concentrations in sedimentcores were measured to evaluate the spatialvariability of HgT deposition, and to establisha chronology of HgT accumulation. Cores takenfrom the northern, middle, and southern sections ofthe bay had similar distribution patterns andconcentrations of HgT, suggesting a common sourceof HgT throughout the bay. Sedimentconcentrations ranged from 190 to 1040 ng Hg g–1,2 to 10 times greater than concentrations expected insediments from non-anthropogenic sources. HgTdeposition rates were similar in different regions ofthe bay, and increased from 200 ng Hg cm–2yr–1in the 1930s to a maximum of 300 ngHg cm–2 yr–1 in the 1960s. Deposition rateshave steadily declined since the 1970s and arecurrently at 80 ng Hg cm–2 yr–1. Transportof HgT by tidal waters from the Hudson River islikely the main source of HgT in the bay.Distribution patterns and absolute concentrations ofMeHg in sediment cores were similar throughout thebay, with concentrations ranging from 0.43 to 2.95ng g–1. Maxima in MeHg concentration profilesoccurred just below the sediment-water interface andat a depth of 30 cm. The maximum at 30 cm wascoincident with maximum HgT concentrations. MeHgconcentrations in suspended particulate matter (SPM)from the Hudson River suggest that MeHg in the baycould be derived from riverine SPM rather than formedin situ.  相似文献   

14.
Nitrate sorption potentials of three surface soils (soils-1-3) were evaluated under different solute concentrations, i.e. 1-100 mg L−1. Batch and diffusion-cell adsorption experiments were conducted to delineate the diffusion property and maximum specific nitrate adsorption capacity (MSNAC) of the soils. Ho’s pseudo-second order model well fitted the batch adsorption kinetics data (R2 > 0.99). Subsequently, the MSNAC was estimated using Langmuir and Freundlich isotherms; however, the best-fit was obtained with Langmuir isotherm. Interestingly, the batch adsorption experiments over-estimated the MSNAC of the soils compared with the diffusion-cell tests. On the other hand, a proportionate increase in the MSNAC was observed with the increase in soil organic matter content (OM) under the batch and diffusion-cell tests. Therefore, increasing the soil OM by the application of natural compost could stop nitrate leaching from agricultural fields and also increase the fertility of soil.  相似文献   

15.
The net mineralization of organic sulfur compounds in surface sediments of Wintergreen Lake was estimated from a mass-balance budget of sulfur inputs and sediment sulfur concentrations. The net mineralization of organic sulfur inputs is <50% complete, which is consistent with the dominance of organic sulfur (>80% of total sulfur) in sediment. Although sediment sulfur is predominantly organic, sulfate reduction is the most significant process in terms of the quantities of sulfur transformed in surface sediments. Rates of sulfate reduction in these sediments average 7 mmol/m2 per day. On an annual basis, this rate is 19-fold greater than net rates of organic sulfur mineralization and 65-fold greater than sulfate ester hydrolysis.  相似文献   

16.
Mercury (Hg) is one of the heavy metal pollutants in the environment. Even a very small amount of mercury can cause serious harm to human beings. Herein, we reported a new carbonothioate‐based fluorescent probe for the detection of Hg2+ without interference from other metal ions. This probe possessed a very large Stokes shift (192 nm), which could improve the detection sensitivity by minimizing the interferences resulted from self‐absorption or auto‐fluorescence. With the addition of Hg2+ to the probe solution, considerable fluorescence enhancement was observed. Additionally, the Hg2+ concentration of 0–16 μM and fluorescence intensity showed a good linear relationship (y = 22106× + 53108, R2 = 0.9955). Finally, the proposed probe was used to detect Hg2+ in real water samples, and its result was satisfactory. Therefore, our proposed probe would provide a promising method for the determination of Hg2+ in the environment.  相似文献   

17.
The heavy use of fertilizers in agricultural lands can result in significant nitrate (NO3) loadings to the aquatic environment. We hypothesized that biological denitrification in agricultural ditches and streams could be enhanced by adding elemental sulfur (So) to the sediment layer, where it could act as a biofilm support and electron donor. Using a bench-scale stream mesocosm with a bed of So granules, we explored NO3 removal fluxes as a function of the effluent NO3 concentrations. With effluent NO3 ranging from 0.5 mg N L−1 to 4.1 mg N L−1, NO3 removal fluxes ranged from 228 mg N m−2 d−1 to 708 mg N m−2 d−1. This is as much as 100 times higher than for agricultural drainage streams. Sulfate (SO42−) production was high due to aerobic sulfur oxidation. Molecular studies demonstrated that the So amendment selected for Thiobacillus species, and that no special inoculum was required for establishing a So-based autotrophic denitrifying community. Modeling studies suggested that denitrification was diffusion limited, and advective flow through the bed would greatly enhance NO3 removal fluxes. Our results indicate that amendment with So is an effective means to stimulate denitrification in a stream environment. To minimize SO42− production, it may be better to place So deeper in the sediment layer.  相似文献   

18.
Adsorption of copper and zinc in lignimerin (an organic material mainly composed by lignin, carbohydrate fragments and some extractives) and its acid derivative (H-lignimerin), recovered from Kraft cellulose mill wastewater was examined. A Box–Behnken experiment design, used to optimize lignimerin recovery process, revealed that the type of solvent used for precipitation is a determining factor in the amount of substance obtained. Conversely, batch adsorption studies at pH 4.0 revealed that the maximum adsorption capacities, modeled by the Langmuir equation, were 666.7 and 370.4 mmol kg−1 for Cu(II) and Zn(II), respectively in lignimerin and 232.6 and 312.5 mmol kg−1 for Cu(II) and Zn(II), respectively in H-lignimerin. The adsorption of Cu(II) and Zn(II) through deprotonated hydroxyl and carboxylic groups was the dominant mechanism that may explain the adsorption in both materials. The adsorption capacities indicated that lignimerin, with a molecular mass between 50 and 70 kDa, has a potential use as an organic sorbent for removing copper and zinc from liquid resources.  相似文献   

19.
Mercury (Hg) is a heavy metal with high toxicity and easy migration; it can be enriched through the food chain, and cause serious threats to the natural environment and human health. So, the development of a method that can be used to detect mercury ions (Hg2+) in the environment, in cells, and in organisms is very important. Here, a new 7‐hydroxycoumarin‐derived carbonothioate‐based probe ( CC‐Hg ) was designed and synthesized for detection of Hg2+. After addition of Hg2+, a large fluorescence enhancement was observed due to the formation of 7‐hydroxyl, which reinforced the intramolecular charge transfer process. The CC‐Hg probe had good water solubility and selectivity. Moreover, the probe was able to detect Hg2+ quantitatively over the concentration range 0–2 μM and with a detection limit of 7.9 nM. Importantly, we successfully applied the probe to detect Hg2+ in water samples, in living cells, and in zebrafish. The experimental results demonstrated its potential value in practical applications.  相似文献   

20.
A pyrene and rhodamine-6G functionalized simple chemosensor L is studied toward sensing of metal ions in solution extensively. L shows selective color change from colorless to pink in the presence of Hg2+ in acetonitrile and the UV-Vis study shows peak at 525 nm with a ε value of 5.2 × 104 M−1 cm−1 due to selective ring opening of rhodamine spirolactam moiety. The selective sensing of Hg2+ by L in the presence of other metal ions and reversible nature of “OFF-ON-OFF” functionality of L by Hg2+ and EDTA, respectively, are also established. The fluorescence study of L in the presence of Hg2+ shows emission at 550 nm when excited at 525 nm (ring opened rhodamine wavelength) or 340 nm (pyrene wavelength) in dry CH3CN. Thus L acts as a selective colorimetric and fluorometric probe (dual probe) for the Hg2+ in solution. Metal ion sensing ability of L is also carried out in water as well as in aqueous Hepes buffer. These studies suggest that the fluorescence output of L in presence of Hg2+ in aqueous environment is apparently due to the generation of acid upon addition of Hg2+ salt in water.  相似文献   

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