Enhanced heavy metal immobilization by a bacterial-chitosan complex in soil

Soil contaminated with heavy metals (e.g., Pb²⁺, Cu²⁺, and Zn²⁺) was treated with aminopoly-saccharide chitosan alone or a strain of the bacterium Bacillus subtilis to determine their effects on metal ion accumulations. Phosphatase and Chitosanase production were also assayed. The combined bacterial-chitosan treatment showed the greater accumulation of Zn²⁺ followed by Cu²⁺ as compared to single treatments, while Pb²⁺ did not show a marked accumulation by either single or combined treatments.     

Biosorption of Cd, Cu, Pb, and Zn from aqueous solutions by the fruiting bodies of jelly fungi (Tremella fuciformis and Auricularia polytricha)

In this study, dried and humid fruiting bodies of Tremella fuciformis and Auricularia polytricha were examined as cost-effective biosorbents in treatment of heavy metals (Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺) in aqueous solution. The humid T. fuciformis showed the highest capacity to adsorb the four metals in the multi-metal solutions. The Pb²⁺ adsorption rates were 85.5%, 97.8%, 84.8%, and 91.0% by dried T. fuciformis, humid T. fuciformis, dried A. polytricha, and humid A. polytricha, respectively. The adsorption amount of Pb²⁺ by dried and humid T. fuciformis in Cd²⁺ + Pb²⁺, Cu²⁺ + Pb²⁺, Pb²⁺ + Zn²⁺, Cd²⁺ + Cu²⁺ + Pb²⁺, and Cd²⁺ + Zn²⁺ + Pb²⁺ solutions were not lower than that in Pb²⁺ solutions. The results suggested that in humid T. fuciformis, Cd²⁺, Cu²⁺, and Zn²⁺ promoted the Pb²⁺ adsorption by the biomass. In the multi-metal solutions of Cd²⁺ + Cu²⁺ + Pb²⁺ + Zn²⁺, the adsorption amount and rates of the metals by all the test biosorbents were in the order of Pb²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺. Compared with the pseudo first-order model, the pseudo second-order model described the adsorption kinetics much better, indicating a two-step biosorption process. The present study confirmed that fruiting bodies of the jelly fungi should be useful for the treatment of wastewater containing Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺.     

Changes in lipid composition in the tissues of fresh-water plant <Emphasis Type="Italic">Hydrilla verticillata</Emphasis> induced by accumulation and elimination of heavy metals

Qualitative and quantitative composition of lipids was investigated in fresh-water vascular plant Hydrilla verticillata (L. fil.) Royle in the course of the accumulation and elimination of heavy metals (HM). The plants were incubated in 100μM solutions of metal nitrates for 10 days. The accumulation of Cu²⁺, Zn²⁺, and Pb²⁺ and their elimination from the plants depended on the duration of exposure and chemical nature of the metal. Accumulation of lead and copper salts was the greatest on the 3rd day, and zinc, on the 10th day. It was associated with changes in the composition of total lipids, polar lipids, and fatty acid (FA). Copper ions suppressed lipid metabolism stronger than other metals. Zn²⁺ and Pb²⁺ induced the accumulation of biomass and elevated the content of some phospholipids and glycolipids. The detected changes (decrease or increase) were observed both during the incubation with HM and within an afterstress period when the plants recovered in the medium free of metals. Judging by their effect on the content of lipids and FA, HM form a series: Cu²⁺ > Zn²⁺ > Pb²⁺. The responses of plant lipid metabolism to the metals of various chemical nature are discussed.     

Maximum values of Ni2+, Cu2+, Pb2+ and Zn2+ in the biomonitor Tillandsia capillaris (Bromeliaceae): Relationship with cell membrane damage

Although several plants belonging to the Bromeliaceae family have been used as heavy metal accumulators in biomonitoring studies, their accumulation ability has not been investigated. The present study obtained the accumulation rates of Ni²⁺, Cu²⁺, Pb²⁺ and Zn²⁺ in leaves of Tillandsia capillaris and revealed their effects on lipid peroxidation by measuring the Malondialdehyde content (MDA). Leaves of T. capillaris were exposed to different metallic solutions of Cu²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ cations. After this exposure period, the accumulation of these ions was measured by Total Reflection X-Ray Fluorescence (TXRF) analysis with Synchrotron Radiation, and the MDA content was calculated. Data sets were evaluated by a one-way analysis of variance (ANOVA) and a fitted regression hyperbola model. The results showed significant differences in the accumulation efficiencies of the cations under study. In addition, the enrichment factor (EF) estimated for these cations was higher for Ni²⁺, suggesting a greater affinity of the plant with this element. Over time, all the metals under study caused significant increases in the MDA content, indicating their toxicity effects even in the most diluted solutions used in this study.     

Inhibition of the biosynthesis ofN-acetylneuraminic acid by metal ions and seleniumin vitro

In liver homogenate the biosynthesis ofN-acetylneuraminic acid usingN-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn²⁺, Mn²⁺, La³⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Ce³⁺, Cd²⁺, Fe²⁺, Fe³⁺, Al³⁺, Sn²⁺, Cs⁺ and Li⁺) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possible several steps of the biosynthesis ofN-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmoll^–1):N-acetylglucosamine kinase (inhibited by Zn²⁺ and vandate), UDP-N-acetylglucosamine-2-epimerase (inhibited by zn²⁺, Co²⁺, Cu²⁺, Hg²⁺, VO ₃ ^– , Pb²⁺, Cd²⁺, Fe³⁺, Cs⁺, Li⁺, selenium(IV) oxide and selenite), andN-acetylmannosamine kinase (inhibited by Zn²⁺, Cu²⁺, Cd²⁺, and Co²⁺). Dose dependent measurements have shown that Zn²⁺, Cu²⁺ and selenite are more efficient inhibitors of UDP-N-acetylglucosamine-2-epimerase than vanadate. As for theN-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn²⁺, Cd²⁺, Co²⁺ and Cu²⁺. In contrast, La³⁺, Al³⁺ and Mn²⁺ (1 mmoll^–1) did not interfere with the biosynthesis ofN-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.Dedicated to Professor Theodor Günther on the occasion of his 60th birthday     

Multimode selective detection of mercury by chiroptical fluorescent sensors based on methionine/cysteine

Two multimode Hg(II) sensors, L‐MethBQA and L‐CysBQA, were obtained by fusing methionine or S‐methyl cysteine, into a bis‐quinolyl amine‐based chiral podand scaffold. Quinolyl groups serve as the fluorophore and possess nitrogen lone pairs capable of chelating metal ions. On exposure to Hg²⁺ or Zn²⁺, these sensors show signal enhancement in fluorescence. However, Cu²⁺ quenches their fluorescence in 30:70 acetontrile/water. L‐CysBQA complexes with Hg²⁺, producing an exciton‐coupled circular dichroism spectrum with the opposite sign to the one that is produced by Cu²⁺ or Zn²⁺ complexation. L‐CysBQA binds Hg²⁺ more strongly than Zn²⁺ and is shown to differentiate Hg²⁺ from other metal ions, such as Zn²⁺, Cu²⁺, Ni²⁺, and Pb²⁺, exceptionally well. The synergistic use of relatively soft sulfur, quinoline‐based chiral ligands and chiroptically enhanced fluorescence detection results in high sensitivity and selectivity for Hg²⁺. Chirality, 2011. © 2011 Wiley‐Liss, Inc.     

Inhibition of nitrogen fixation in alfalfa by arsenate, heavy metals, fluoride, and simulated Acid rain

The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F⁻ and 42% inhibition by 100 micrograms Pb²⁺ per milliliter, to 100% inhibition by 10 micrograms Cd²⁺ per milliliter and 100 micrograms per milliliter As, Cu²⁺, and Zn²⁺ ions. Zn²⁺ showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn²⁺ > Cd²⁺ > Cu²⁺ > AsO₃⁻ > Pb²⁺ > F⁻. The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb²⁺ was applied, but was 1,000 times more sensitive to Zn²⁺. The relationship of the data to field conditions and industrial pollution is discussed.     

重金属铜、锌、镉复合胁迫对麻疯树幼苗生理生化的影响

该研究以Cu~(2+)、Zn~(2+)、Cd~(2+)单一胁迫为对照,探讨不同浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫对麻疯树幼苗生理生化指标的影响。结果表明:随着Cu~(2+)、Zn~(2+)、Cd~(2+)浓度的增加,麻疯树幼苗叶片中的蛋白质(Pro)、丙二醛(MDA)含量均逐渐增加,其叶片叶绿素含量随着Zn~(2+)胁迫浓度的增加呈现出先降后升的趋势,在中等浓度(100 mg·L-1)的Zn~(2+)胁迫时含量最低、随着Cu~(2+)胁迫浓度的增加叶绿素含量先升高后降低,在Cu~(2+)浓度为200 mg·L-1时含量最高,达到1 200 mg·g-1FW; Cd~(2+)胁迫对叶绿素含量和根系活力无明显影响。根系活力在Zn~(2+)浓度为100 mg·L~(-1)时最强,随着Cu~(2+)浓度的增加而减弱。低浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)对过氧化物酶活性和可溶性糖含量都具有促进作用。Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫时对可溶性蛋白、叶绿素和丙二醛含量均无明显影响,随着复合胁迫时浓度的增加,可溶性糖含量和根系活力先增后减。这表明麻疯树对三种重金属的胁迫具有一定的抗性,过高浓度的胁迫会影响麻疯树幼苗生理生化的一些指标,但是麻疯树可以通过自身的防御系统使伤害降到最小。此外,重金属复合胁迫可以在一定程度上减轻单一胁迫对麻疯树幼苗造成的毒害作用。     

Effects of heavy metal cations on the mitochondrial ornithine/citrulline transporter reconstituted in liposomes

The effect of heavy metal cations on the mitochondrial ornithine/citrulline transporter was tested in proteoliposomes reconstituted with the protein purified from rat liver. The transport activity was measured as [³H]ornithine uptake in proteoliposomes containing internal ornithine (ornithine/ornithine antiport mode) or as [³H]ornithine efflux in the absence of external substrate (ornithine/H⁺ transport mode). 0.1 mM Cu²⁺, Pb²⁺, Hg²⁺, Cd²⁺ and Zn²⁺ strongly inhibited (more than 85%) the antiport; whereas Mn²⁺, Co²⁺ and Ni²⁺ inhibited less efficiently (25, 47 and 69%, respectively). The IC₅₀ values of the transporter for the different metal ions ranged from 0.71 to 350 μM. Co²⁺ and Ni²⁺ also inhibited the [³H]ornithine efflux whereas Cu²⁺, Pb²⁺, Hg²⁺, Cd²⁺ and Zn²⁺ stimulated the [³H]ornithine efflux. The stimulation of the [³H]ornithine efflux by Cu²⁺ and Cd²⁺ (as well as by Pb²⁺, Hg²⁺ and Zn²⁺) was not prevented by NEM and was reversed by DTE. These features indicated that the inhibition of the antiport was due to the interaction of the Cu²⁺, Pb²⁺, Hg²⁺, Cd²⁺ and Zn²⁺ with a population of SH groups, of the transporter, responsible for the inhibition of the physiological function; whereas the stimulation of [³H]ornithine efflux was due to the induction of a pore-like function of the transporter caused by interaction of cations with a different population of SH groups. Differently, the inhibition of the ornithine transporter by Ni²⁺, Co²⁺ or Mn²⁺ was caused by interaction with the substrate binding site, as indicated by the competitive or mixed inhibition.     

径流雨水中溶解性有机质特征演化及其对典型污染物迁移和生物有效性的影响

地表径流污染已经逐渐成为城市面源污染的重要组成部分。其中溶解性有机质DOM (Dissolved organic matter)是有机污染物的主要组成部分。DOM中因为含有大量不饱和结构、官能团,其中包括羟基、羧基、羰基、胺基等,这些结构容易与径流中重金属结合发生络合反应,改变重金属的赋存形态,从而对其迁移转化及其生物有效性产生很大的影响。本文以北京市地表径流为研究对象,研究城市地表径流在冬、夏季不同功能区不同下垫面中溶解性有机质特征及其与典型重金属的作用机制,通过荧光淬灭滴定实验,研究夏季径流雨水中DOM的不同组分与重金属Cu~(2+)、Pb~(2+)、Zn~(2+)之间的结合机制。研究结果显示PARAFAC将获得的样品都分解成2类6个不同的组分,1种腐殖酸,1种类蛋白;类蛋白物质的荧光强度与Cu~(2+)、Pb~(2+)的淬灭率要强于腐殖酸,而Zn~(2+)则呈现相反趋势;通过使用二维相关同步光谱发现DOM对重金属Cu~(2+)、Pb~(2+)、Zn~(2+)的敏感性呈现递减趋势,二维相关异步光谱发现Cu~(2+)、Pb~(2+)会先与位于270—300nm附近类蛋白光谱带反应,Zn~(2+)则会先与330nm附近的腐殖酸光谱带反应。     

Effects of heavy metals on seed germination and early seedling growth of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Seed is a developmental stage that is highly protective against external stresses in the plant life cycle. In this study, we analyzed toxicity of essential (Cu²⁺ and Zn²⁺) and non-essential heavy metals (Hg²⁺, Pb²⁺ and Cd²⁺) on seed germination and seedling growth in the model species Arabidopsis. Our results show that seedling growth is more sensitive to heavy metals (Hg²⁺, Pb²⁺, Cu²⁺ and Zn²⁺) in comparison to seed germination, while Cd²⁺ is the exception that inhibited both of these processes at similar concentrations. To examine if toxicity of heavy metals is altered developmentally during germination, we incubated seeds with Hg²⁺ or Cd²⁺ only for a restricted period during germination. Hg²⁺ displayed relatively strong toxicity at period II (12–24 h after imbibition), while Cd²⁺ was more effective to inhibit germination at period I (0–12 h after imbibition) rather than at period II. The observed differences are likely to be due in part to selective uptake of different ions by the intact seed, because isolated embryos (without seed coat and endosperm) are more sensitive to both Hg²⁺ and Cd²⁺ at period I. We assessed interactive toxicity between heavy metals and non-toxic cations, and found that Ca²⁺ was able to partially restore the inhibition of seedling growth by Pb²⁺ and Zn²⁺.     

Comparison of the Adsorption Capabilities of Myriophyllum spicatum and Ceratophyllum demersum for Zinc,Copper and Lead

Industrial wastewaters contain various heavy metal components and therefore threaten aquatic bodies. Heavy metals can be adsorbed by living or non‐living biomass. Submerged aquatic plants can be used for the removal of heavy metals. This paper exhibits the comparison of the adsorption properties of two aquatic plants Myriophyllum spicatum and Ceratophyllum demersum for lead, zinc, and copper. The data obtained from batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q_max) were obtained for both plant species and each metal. The maximum adsorption capacities (q_max) achieved with M. spicatum were 10.37 mg/g for Cu²⁺, and 15.59 mg/g for Zn²⁺ as well as 46.49 mg/g for Pb²⁺ and with C. demersum they were 6.17 mg/g for Cu²⁺, 13.98 mg/g for Zn²⁺ and 44.8 mg/g for Pb²⁺. It was found that M. spicatum has a better adsorption capacity than C. demersum for each metal tested. Gibbs free energy and the specific surface area based on the q_max values were also determined for each metal.     

Chimeras of P-type ATPases and their transcriptional regulators: contributions of a cytosolic amino-terminal domain to metal specificity

Zn²⁺‐responsive repressor ZiaR and Co²⁺‐responsive activator CoaR modulate production of P₁‐type Zn²⁺‐ (ZiaA) and Co²⁺‐ (CoaT) ATPases respectively. What dictates metal selectivity? We show that Δ ziaΔcoa double mutants had similar Zn²⁺ resistance to Δzia single mutants and similar Co²⁺ resistance to Δcoa single mutants. Controlling either ziaA or coaT with opposing regulators restored no resistance to metals sensed by the regulators, but coincident replacement of the deduced cytosolic amino‐terminal domain CoaT_N with ZiaA_N (in ziaR‐_p ziaA‐ziaA_NcoaT) conferred Zn²⁺ resistance to ΔziaΔcoa, Zn²⁺ content was lowered and residual Co²⁺ resistance lost. Metal‐dependent molar absorptivity under anaerobic conditions revealed that purified ZiaA_N binds Co²⁺ in a pseudotetrahedral two‐thiol site, and Co²⁺ was displaced by Zn²⁺. Thus, the amino‐terminal domain of ZiaA inverts the metals exported by zinc‐regulated CoaT from Co²⁺ to Zn²⁺, and this correlates simplistically with metal‐binding preferences; K_ZiaAN Zn²⁺ tighter than Co²⁺. However, Zn²⁺ did not bleach Cu⁺‐ZiaA_N, and only Cu⁺ co‐migrated with ZiaA_N after competitive binding versus Zn²⁺. Bacterial two‐hybrid assays that detected interaction between the Cu⁺‐metallochaperone Atx1 and the amino‐terminal domain of Cu⁺‐transporter PacS_N detected no interaction with the analogous, deduced, ferredoxin‐fold subdomain of ZiaA_N. Provided that there is no freely exchangeable cytosolic Cu⁺, restricted contact with the Cu⁺‐metallochaperone can impose a barrier impairing the formation of otherwise favoured Cu⁺–ZiaA_N complexes.     

Effect of heavy metals on the glutathione status in different ectomycorrhizal <Emphasis Type="Italic">Paxillus involutus</Emphasis> strains

The glutathione (GSH) status and heavy metal tolerance were investigated in four Paxillus involutus strains isolated from different heavy-metal-polluted and non-polluted regions of Europe. The heavy metal burden in the habitats did not affect significantly either the heavy metal (Cr₂O₇²⁻, Cd²⁺, Hg²⁺, Pb²⁺, Zn²⁺, Cu²⁺) tolerance and accumulation or the GSH production of the strains tested. Exposures to heavy metals increased the intracellular GSH concentrations in 12 from 24 experimental arrangements (four strains exposed to six heavy metals) independently of the habitats of the strains. The importance of GSH in heavy metal tolerance (high MIC values, ability to accumulate heavy metals and to grow in the presence of heavy metals) was thus demonstrated in this ectomycorrhizal fungus.     

Heavy metal ion inhibition studies of human,sheep and fish α-carbonic anhydrases

Carbonic anhydrases (CAs, EC 4.2.1.1) were purified from sheep kidney (sCA IV), from the liver of the teleost fish Dicentrarchus labrax (dCA) and from human erythrocytes (hCA I and hCA II). The purification procedure consisted of a single step affinity chromatography on Sepharose 4B-tyrosine-sulfanilamide. The kinetic parameters of these enzymes were determined for their esterase activity with 4-nitrophenyl acetate as substrate. The following metal ions, Pb²⁺, Co²⁺, Hg²⁺, Cd²⁺, Zn²⁺, Se²⁺, Cu²⁺, Al³⁺ and Mn³⁺ showed inhibitory effects on these enzymes. The tested metal ions inhibited these CAs competitively in the low milimolar/submillimolar range. The susceptibility to various cations inhibitors differs significantly between these vertebrate α-CAs and is probably due to their binding to His64 or the histidine cluster.     

The Effect of Copper and Lead Ions on Growth and Lipid Composition of the Fern Matteuccia sthruthiopteris

In the present study, the effect of copper (Cu²⁺) and lead (Pb²⁺) ions on the growth and lipid composition of various parts of the fern, Matteuccia sthruthiopteris, was examined. Plants were incubated in the presence or absence of 1, 10, 100 μM of Cu(NO₃)₂ or Pb(NO₃)₂. Cu²⁺ and Pb²⁺ ions at concentrations of 1 and 10 μM caused an increased growth of the roots and leaves. A higher concentration of Pb²⁺ did not show any effect on growth, whereas that of Cu²⁺ slowed down the growth of the whole plants. The roots accumulated more than 700 μg of Cu²⁺ and 400 μg of Pb²⁺ per 1 g dry weight when the plants were incubated with the higher concentrations of metals, whereas in the leaves the concentration of Cu²⁺ was much lower and did not exceed 12 μg/g dry weight. No accumulation of Pb²⁺ ions by leaves was detected. The lipid composition of photosynthetic leave tissues was shown to be affected by the presence of metal ions in the root medium at either concentration studied. Various changes in lipid classes were noted as responsive reactions of M. sthruthiopteris to the heavy metal ions in nutrient medium. Cu²⁺ ions decreased the content of total lipids, total phospholipids, and individual phosphatidylcholines and phosphatidylethanolamines, whereas Pb²⁺ ions caused a decrease in the content of total lipids and glycolipids. Changes in the lipid composition were more pronounced in the mature leaves than in the scrolls of the studied fern.     

Effect of heavy metal ions on growth and biochemical characteristics of photosynthesis of barley and maize seedlings

The effects of Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ on growth and the biochemical characteristics of photosynthesis were more expressed in barley (Hordeum vulgare L.) than in maize (Zea mays L.) seedlings. The barley and maize seedlings exhibited retardation in shoot and root growth after exposure of Cu²⁺, Cd²⁺ and Pb²⁺. The Zn²⁺ions practically did not influence these characteristics. The total protein content of barley and maize roots declined with an increase in heavy metal ion concentrations. The protein content of barley shoots was only slighly decreased with an increase in heavy metal ion concentrations, but the protein content in maize shoots was increased under the same conditions. The chlorophyll content was decreased in barley shoots and increased in maize. The ribulose-l,5-bisphosphate carboxylase (RuBPC, EC 4.1.1.39) and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activities were decreased drastically by Cu²⁺, Cd²⁺ and Pb²⁺ in thein vivo experiments. The tested heavy metal ions affect photosynthesis probably mainly by inhibition of these key carboxylating enzymes: this mechanism was studied in thein vitro experiments.     

Effects of heavy metals on the Ca2+-ATPase activity present in gill cell plasma-membrane of mussels (Mytilus galloprovincialis Lam.)

1. Heavy metals (Hg²⁺, Cu²⁺, Cd²⁺, Zn²⁺, Pb²⁺) at micromolar concentrations strongly inhibit the Ca²⁺-ATPase activity present in the plasma-membrane obtained from the gill cells of Mytilus galloprovincialis Lam. Heavy metals act through inhibition of the formation of the phosphorylated intermediate.2. All the heavy metals tested inhibit the Ca²⁺-ATPase activity, the effect following the order: Hg²⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺; the simultaneous addition of different heavy metals causes a summatory inhibition of the enzyme activity; addition to the reaction mixture of GSH at a final concentration of 0.5 mM, reverses inhibitory effects of heavy metals.3. The inhibitory effects of Cu²⁺ on Ca²⁺-ATPase are highly enhanced by addition of ascorbate to the reaction mixture. In the presence of ascorbate (100 μM), copper strongly stimulates the lipid peroxidation damage of the gill plasma-membranes, a result that may explain the high copper cytotoxicity.     

Inhibition of Na+/K+-ATPase and Mg2+-ATPase by metal ions and prevention and recovery of inhibited activities by chelators

Kinetics and inhibition of Na⁺/K⁺-ATPase and Mg²⁺-ATPase activity from rat synaptic plasma membrane (SPM), by separate and simultaneous exposure to transition (Cu²⁺, Zn²⁺, Fe²⁺ and.Co²⁺) and heavy metals (Hg²⁺and Pb²⁺) ions were studied. All investigated metals produced a larger maximum inhibition of Na⁺/K⁺-ATPase than Mg²⁺-ATPase activity. The free concentrations of the key species (inhibitor, MgATP^{2 ?} , MeATP^{2 ?} ) in the medium assay were calculated and discussed. Simultaneous exposure to the combinations Cu²⁺/Fe²⁺ or Hg²⁺/Pb²⁺caused additive inhibition, while Cu²⁺/Zn²⁺ or Fe²⁺/Zn²⁺ inhibited Na⁺/K⁺-ATPase activity synergistically (i.e., greater than the sum metal-induced inhibition assayed separately). Simultaneous exposure to Cu²⁺/Fe²⁺ or Cu²⁺/Zn²⁺ inhibited Mg²⁺-ATPase activity synergistically, while Hg²⁺/Pb²⁺ or Fe²⁺/Zn²⁺ induced antagonistic inhibition of this enzyme. Kinetic analysis showed that all investigated metals inhibited Na⁺/K⁺-ATPase activity by reducing the maximum velocities (V_max) rather than the apparent affinity (K_m) for substrate MgATP^2-, implying the noncompetitive nature of the inhibition. The incomplete inhibition of Mg²⁺-ATPase activity by Zn²⁺, Fe²⁺ and Co²⁺ as well as kinetic analysis indicated two distinct Mg²⁺-ATPase subtypes activated in the presence of low and high MgATP^{2 ?} concentration. EDTA, L-cysteine and gluthathione (GSH) prevented metal ion-induced inhibition of Na⁺/K⁺-ATPase with various potencies. Furthermore, these ligands also reversed Na⁺/K⁺-ATPase activity inhibited by transition metals in a concentration-dependent manner, but a recovery effect by any ligand on Hg²⁺-induced inhibition was not obtained.     

A novel optical probe based on d‐penicillamine‐functionalized graphene quantum dots: Preparation and application as signal amplification element to minoring of ions in human biofluid

In this study, d ‐penicillamine‐functionalized graphene quantum dots (DPA‐GQD) has been synthesized, which significantly increases the fluorescence intensity of GQD. We used this simple fluorescent probe for metal ions detection in human plasma samples. Designed DPA‐GQD respond to Hg²⁺, Cu²⁺, Au²⁺, Ag⁺, Co²⁺, Zn²⁺, and Pb²⁺ with high sensitivity. The fluorescence intensity of this probe decreased significantly in the presence of metal ions such as, Hg²⁺, Cu²⁺, Au²⁺, Ag⁺, Co²⁺, Zn²⁺, and Pb²⁺. In this work, a promising probe for ions monitoring was introduced. Moreover, DPA‐GQD probe has been tested in plasma samples. The functionalized DPA‐GQDs exhibits great promise as an alternative to previous fluorescent probes for bio‐labeling, sensing, and other biomedical applications in aqueous solution.