Influence Of Cd2 Research Articles

Discussion on the applicability and mechanism of phosphate-based geopolymers used for cadmium and cadmium-lead heavy metals solidification/stabilization

Lead (Pb2+) and cadmium (Cd2+) are common heavy metal pollution, which is harmful to humans and animals. However, the diffusion rate of heavy metal ions moves faster in acidic environment, there are a large number of acidic heavy metal polluted soil in China, but the conventional binders are not effective to deal with them. Phosphate-based geopolymers (PGEOs) are acidic materials, and have excellence mechanical properties in acidic environment and solidification/stabilization (S/S) effect on Pb2+, but the applicability of PGEOs to Cd, Pb and Cd composite pollution is not clear. Therefore, this study discusses the applicability of PGEOs fabricated from fly ash (FA) and aluminum dihydrogen phosphate (ADP) as activator for S/S treatment of Cd, Pb-Cd composite pollution. Results show that the influence of Cd2+ and Pb2+ on the compressive strength of PGEOs was inconsistent, as the Cd2+ content raised, the compressive strength reduced slightly at 7 and 14 days, but it did not change basically at 28 days. However, the compressive strength rose firstly and then declined with an increase in Pb-Cd content when partial Pb2+ was used to replace Cd2+. The compressive strength of PGEOs with a Pb-Cd content of 0.6 % reached maximum (11.45 MPa), exceeding the compressive strength of PGEOs containing Cd2+. Moreover, the PGEOs presents an excellent stabilization effect on Pb2+, but poor effect on Cd2+. The Pb2+ leaching concentration meet the hazardous solid waste identification criteria (<5 mg/L), but the Cd2+ leaching is high and is more than 1 mg/L. Furthermore, the compressive strength of PGEOs had a good correlation with pH and EC. The S/S mechanism of PGEOs for Pb2+, Cd2+ includes physical adsorption, encapsulation, and chemical precipitation. However, Pb2+ involved in the geopolymerization process, while Cd2+ can not participate in the structure formation, so the PGEOs have a poor S/S effect. Therefore, it needs to be further improved when using PGEOs to stabilize acidic Cd2+ contaminated soil.

Effects of Cd2+ and Pb2+ on enantioselective degradation behavior of α-cypermethrin in soils and their combined effect on activities of soil enzymes

Heavy metals may coexist with pesticides in farmland through wastewater irrigation, application of pesticides and chemical fertilizers, or unappropriated waste disposal. Heavy metals are toxic to soil microorganism, which may influence the environmental behavior of pesticides subsequently. In this study, the influence of Cd2+ and Pb2+ on the degradation of α-cypermethrin and its metabolites, 3-phenoxphenoxybenzoic acid (3-PBA) and 3-(2',2'-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCCA), were investigated through soil incubation experiment. It was found heavy metals like Cd2+ and Pb2+ will inhibit the degradation of α-cypermethrin, especially at high concentrations. Pb2+ has a stronger inhibitory effect on the degradation of α-cypermethrin than Cd2+ in the same concentration. With the presence of 10 mg/kg Pb2+, the half-life of α-cypermethrin increased from 41.1 to 99.9 days, even the half-life was 129.3 days with 50 mg/kg of Pb2+. Besides, heavy metals influenced the chiral selective degradation of α-cypermethrin. The enantiomer fraction was near 0.5 when 10 mg/kg of heavy metals existed. Furthermore, the adverse effects of heavy metals on soil urease, catalase, and sucrase activity were assayed. In tested concentrations (10 and 50 mg kg-1), the heavy metals result in strong inhibition of the activity of the enzymes present on soil, jeopardizing the biodegradation by the microbiome and which may inhibit the degradation of α-cypermethrin.

Influence of metal cation and surface iron oxide on the transport of sulfadiazine in saturated porous media

Sulfadiazine (SDZ) is an antibiotic frequently detected in soil and groundwater. The transport of SDZ in subsurface environment is a critical process affecting its retention in soil. To date, the effects of iron oxide and metal cation on the transport of SDZ remain largely unknown, so we investigated the transport properties of SDZ in cleaned and iron oxides coated quartz sand, as affected by the presence of conventional cations (Ca2+, Mg2+, K+, and Na+) and Cd2+ through column experiments and simulation. We found that iron oxide coating on sand surface inhibited the transport of SDZ, mainly due to hydrophobic effect, complexation, and electrostatic attraction. The inhibitory effect became more marked with increasing concentration of Cd2+. It favors the transport of Cd2+ due to the electrostatic repulsion between positively charged iron oxide and Cd2+. Ca2+ promoted the transport of SDZ in coated sand, while all the conventional cations had no effect on the transport of SDZ in cleaned sand. The increase in the concentration of Cd2+ favors the transport of SDZ in cleaned sand. However, in iron oxide coated sand, the influence of Cd2+ on the transport of SDZ was dependent on the concentration of Cd2+. At lower concentration of Cd2+ and by competition, the transport is favored. At high concentration, the transport is inhibited mainly due to the formation of ternary surface complexes. A convective–dispersive transport model was applied to simulate and interpret experimental data. Breakthrough curves fitted well with a one-site model (OSM), indicating that SDZ adsorption on the sand experiences reversible kinetic. A low level of KF values with nearly linear sorption isotherm shows high mobility of SDZ and a high potential risk of surface and groundwater contamination. However, such high mobility can be reduced by increasing the content of iron oxides in porous media.

Cadmium-affected synthesis of exopolysaccharides by rhizosphere bacteria.

Study is focused on the influence of cadmium addition to growth media on production yield, their size and molecular mass of exopolysaccharides (EPS) synthesized by three rhizosphere bacteria strains. Inhibition of bacterial growth by increasing concentrations of Cd2+ was also analysed. The highest impact of Cd2+ was noticed on the growth of Arthrobacter sp. and Rhizobium metallidurans. Chryseobacterium sp. and Arthrobacter sp. produced significantly lower when compared to R. metallidurans amounts of EPS under the influence of Cd2+ . In all bacterial strains both size and molecular mass decreased after addition of Cd2+ to growth media. It causes a change in EPS conformation to more planar, which minimizes the volume of liquid in the interglobular space next to the bacterial wall. Results confirmed strong effect of Cd2+ on the structure and synthesis of bacterial EPS what can be a key factor in the interactions between rhizosphere bacteria and host plants in heavy metal polluted soils. This work proves that due to the presence of cadmium ions, the size and conformation of EPS produced by selected bacterial strains is changed to minimize their impact on cell. We suggest that shifting in EPS conformation from bigger globular particles to the smaller planar ones could be one of the probable mechanisms of Cd resistance in metallotolerant bacteria, and finally explain increased efficiency of heavy metal phytoextraction by EPS-producing plant growth-promoting micro-organisms. One of the most promising remediation technique for Cd-contaminated areas is the phytoremediation in which rhizosphere bacteria play an important role by protecting plants' roots from toxic condition thus enhancing efficiency of intake. EPS secretion by bacteria is one of the most common mechanisms to protect the cell from impact of unpleasant environmental conditions, for example, toxicity of heavy metals like Cd.

Вплив iонiв Сd2+ на активнiсть стромальних карбоангiдраз хлоропластiв шпинату

Вплив iонiв Сd2+ на активнiсть стромальних карбоангiдраз хлоропластiв шпинату

Effect of Cd2+ on early hydration process of magnesium phosphate cement and its leaching toxicity properties

Abstract Cadmium pollution is a type of heavy-metal pollution that is harmful to human health and the environment. Magnesium phosphate cement (MPC) is a fast-setting material with rapid strength development that can solidify and stabilize pollutants quickly. Hence, it has excellent potential for the stabilization/solidification of cadmium pollutants and the rapid reduction of the environmental toxicity of cadmium ions. However, there has been insufficient research into the influence of Cd2+ on the early hydration process of MPC. This paper studies the effect of cadmium ions on the setting time, compressive strength, pH change tendency, and heat of hydration at the onset of hydration on the performance of MPCs with different magnesia to phosphate ratios and cadmium ion content. The results demonstrate that the strength of MPC was reduced and the setting time delayed with higher additions of Cd2+. However, the addition had minimal effect on the tendency of pH change in the MPC system. The addition of Cd2+ slowed the hydration rate of MPC; the total heat release was also reduced. When the M/P ratio of MPC was 4:1, the compressive strength of the sample decreased from 32.32 MPa to 9.05 MPa; the final solidification time of the sample increased from 686 s to 838 s by adding 4% cadmium nitrate. The hydrated products were analyzed by XRD, SEM, and EDS. It was determined that the addition of cadmium ions did not produce new apparent crystalline phases. The quantity of cadmium ion leached was below the standard requirement, which is the most critical factor for the solidification of cadmium ions. The results indicate that MPC is beneficial in the stable solidification of cadmium ions.

Enhanced tolerance of Deschampsia antarctica Desv. to the mutagenic effect of cadmium ions

Aim. To study the potential effects of different concentrations of cadmium ions on antarctic plant D. antarctica using PCR analysis. Methods. Plants were grown in vitro on B5 Gamborg and Eveleigh agar medium supplemented with CdCl2. Genetic rearrangements were studied by PCR-analysis using ISSR- and IRAP-primers. Results. Genetically identical plants of D. antarctica obtained by microclonal propagation in vitro were used for the study of mutagenic effect of cadmium ions. The influence of Cd2+ was investigated within the concentration ranging from 0.1 to 10 mM. The results of cultivation of D. antarctica plants in the presence of cadmium ions for 63 days allow to determine the concentration range that does not inhibit the growth of the plants in vitro, and it was up to 1 mM. It was found that toxicant concentrations of 0.1 and 0.2 mM did not cause changes in the profiles of PCR products. After growing the plants with 0.2–1 mM CdCl2 for 17 days, the changes in the profiles of PCR products, indicating the mutagenic impact, were observed at concentrations of 0.6 mM or above; moreover, the number of changes increased in dependence on the concentration of heavy metal. Prolonged influence (140-265 days) of cadmium ions in relatively low concentrations (0.1 mM and 0.4 mM) did not cause detectable mutations. Conclusions. D. antarctica, a plant extremophile, which has evolved mechanisms of resistance to a variety of extreme conditions as a result of adaptation to the existence in the harsh conditions of Antarctica, shows enhanced resistance to cadmium ions in comparison with other species of vascular plants. Inhibition of growth occurs at Cd2+ concentrations of 0.1 mM or above, whereas concentrations of 1 mM or above cause cessation of growth and death of plants. Mutagenic effect on D. antarctica was observed at Cd2+ concentrations of above 0.4 mM. After prolonged growth of plants (for 3–8 months) at cadmium ions concentrations of 0.1–0.4 mM, genetic changes was not found.Keywords: Deschampsia antarctica Desv., plants in vitro obtained by microclonal propagation, cadmium ions, mutagenic effect, PCR-analysis.

Cd^2+、Cu^2+胁迫对黑藻（Hydrilla verticillata）的生长及光合荧光特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 Cd2+、Cu2+胁迫对黑藻(Hydrilla verticillata)的生长及光合荧光特性的影响 DOI: 10.5846/stxb201408081588 作者: 作者单位: 江西师范大学生命科学学院,江西师范大学生命科学学院,江西师范大学,江西师范大学生命科学学院,江西师范大学生命科学学院,江西鄱阳湖南矶山湿地国家级自然保护区管理局 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41161035, 41461042);国家科技部"十二五"科技支撑计划资助项目(2011BAC13B02);江西省重大生态安全问题监控协同创新中心资助项目(JXS-EW-03);江西省科技支撑计划项目(20133BBG70005);江西省亚热带植物资源保护与利用重点实验室开放基金资助项目(YRD201314) Influence of Cd2+ or Cu2+ stress on the growth and photosynthetic fluorescence characteristics of Hydrilla verticillata Author: Affiliation: College of Life Sciences,Jiangxi Normal University,Jiangxi Provincial Key Lab of Protection and Utilization of Subtropical Plant Resources,College of Life Sciences, Jiangxi Normal University,Jiangxi Provincial Key Lab of Protection and Utilization of Subtropical Plant Resources,Key Laboratory of Poyang Lake Wetland and Watershed Research,Ministry of Education,Jiangxi Normal University,College of Life Sciences, Jiangxi Normal University,Jiangxi Provincial Key Lab of Protection and Utilization of Subtropical Plant Resources,College of Life Sciences,Jiangxi Normal University,Jiangxi Provincial Key Lab of Protection and Utilization of Subtropical Plant Resources,Jiangxi Nanji Wetland National Nature Reserve Bureau Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以黑藻(Hydrilla verticillata)为供试材料,采用Cd2+和Cu2+等两种重金属分别在5个浓度梯度水平下的河砂水培方法,研究Cd2+或Cu2+不同浓度胁迫对黑藻株高、生物量、成活率和叶绿素含量的影响,以及对黑藻叶片最小荧光(Fo)、最大荧光(Fm),PSⅡ最大量子产率(QYmax,)、稳态下的PSⅡ反应中心关闭程度(1-Qp_Lss)、稳态下的非光化学淬灭(NPQ_Lss)等光合荧光参数及其荧光成像的影响,探讨各个参数分别随镉、铜浓度递增的变化规律。研究结果表明,Cd2+胁迫下黑藻的株高显著下降,说明Cd2+可能对黑藻叶片的维管束结构产生伤害作用;Cd2+和Cu2+胁迫对黑藻鲜重均无显著影响,说明与水生植物自由水含量存在一定关系;Cd2+和Cu2+胁迫均使黑藻干重显著下降,其中Cu2+胁迫对黑藻干重的影响更显著,说明Cu2+胁迫对黑藻累积生物量的影响远大于Cd2+;Cd2+和Cu2+胁迫下叶绿素各值均呈下降趋势,而Cu2+胁迫对叶绿素的影响更大,说明Cu2+对黑藻叶绿体的毒害比Cd2+更大。随着Cd2+或Cu2+胁迫浓度梯度的增加,黑藻的叶绿素荧光参数(Fo、Fm、QYmax)呈显著下降趋势,(1-Qp_Lss)呈上升趋势,而NPQ_Lss先上升后下降。黑藻在不同重金属胁迫下的生理指标、荧光参数及成像特征等方面所表现出的变化差异性,反映出同等浓度下黑藻受重金属胁迫的影响程度为:Cd2+胁迫>Cu2+胁迫;黑藻可以在Cu2+浓度低于1 mg/L的环境下具有正常的光合活性,可推测将黑藻用于低浓度Cu污染水域的修复;在Cu2+浓度达3 mg/L以上环境下黑藻即无法长时间生存,可推测黑藻可以作为Cd污染水环境的指示种。 Abstract:In this study, we selected the aquatic plant Hydrilla verticillata as our specimen and cultured it in clean river sand and water in order to study the influence of five separate concentration levels of Cd2+ or Cu2+ on the plant. Effects of the stress on the plant were identified, and we recorded parameters such as height, biomass, chlorophyll content, and survival ratios of H. verticillata, as well as the effects of fluorescence parameters such as minimal fluorescence (Fo), maximal fluorescence (Fm), PS II maximum quantum yield (QYmax), degree of PSⅡ reaction centers closed under stable state (1-Qp_Lss), non-photochemical quenching under stable state (NPQ_Lss), and fluorescence images of H. verticillata leaves. We also separately studied the variation characteristics of each parameter of H. verticillata under the stress of increasing Cd2+ or Cu2+ concentrations. We found that the height of H. verticillata decreased significantly under the different levels of pollution stress by the heavy metal Cd2+. This indicated that Cd2+ pollution may damage the bundle structure of H. verticillata. There were no significant effects on the fresh weight of H. verticillata under the stress of either Cd2+ or Cu2+ pollution, and this may be related to the high content of free water in aquatic plants. Dry weight of H. verticillata decreased significantly when the plants were exposed to Cd2+ or Cu2+ pollution. Effect of Cu2+ pollution on the dry weight of H. verticillata was far more prominent than that of Cd2+ pollution. All chlorophyll values decreased significantly when the plants were subjected to Cd2+ or Cu2+ pollution, and we found that the effect of Cu2+ pollution was greater than that of Cd2+ pollution. This suggested that the toxicity of Cu2+ against H. verticillata chloroplasts is greater than that of Cd2+. The chlorophyll fluorescence parameters (Fo, Fm, and QYmax) of H. verticillata under Cd2+ or Cd2+ stress were significantly lower than those of the control groups; however, the values of (1-Qp_Lss) increased, and the values of NPQ_Lss first increased and then decreased as the concentrations of the heavy metals increased. The different values for the physiological parameters, fluorescence parameters, and imaging characteristics indicated that the influence of Cd2+ on H. verticillata was greater than that of Cu2+ when the same concentrations of the two different heavy metals were used. When Cu2+ concentration was lower than 1 mg/L in the water environment, photosynthetic activities of H. verticillata under Cu2+ stress were almost normal. This means that H. verticillata could be used to restore a water environment with a low Cu2+ concentration. H. verticillata cannot survive for a long time in a water environment contaminated with Cd2+ or if Cu2+ concentrations reach or exceed 3 mg/L. This means that H. verticillata could be used as an indicator species for water contaminated with Cd2+. 参考文献 相似文献 引证文献

Enhancing photoelectrochemical performance of TiO2 nanotube arrays by CdS and Bi2S3 co-sensitization

TiO2 nanotube arrays (TiO2 NTs) were prepared by a two-step anodization of titanium foils in ethylene glycol electrolyte. Then, CdS and Bi2S3 nanoparticles were deposited on TiO2 NTs by an one-pot solvothermal method. The investigations of X-ray diffraction and scanning electron microscopy indicated that CdS and Bi2S3 nanoparticles grew uniformly on the surface of TiO2 NTs. UV–vis absorption and photoelectrochemical measurements proved that the CdS and Bi2S3 co-sensitization significantly improved the visible light absorption, photocurrent response and photoelectrocatalytic removal of RhB and Cr(VI). In addition, the influence of Cd2+/Bi3+ concentration ratios on the photoelectrochemical performance of TiO2 NTs-CdS/Bi2S3 was investigated in detail. The TiO2 NTs-CdS/Bi2S3 (1:1) showed an optimal photoelectrochemical activity which could be attributed to the improvement of visible light response and charge separation derived from the coupling effect of CdS/Bi2S3 nanoparticles.

Analysis of microbiologically stimulated biomass of Salix viminalis L. in the presence of Cd2+ under in vitro conditions – implications for phytoremediation

AbstractThe efficiency of phytoremediation might be highly affected by plant-associated microorganisms, and understanding of the underlying mechanisms is still a great challenge. The primary aim of this study was to evaluate the efficiency parameters for Cd2+accumulation in the biomass of willow (Salix viminalis) as well as to define the biochemical response of the host plant when it is inoculated with selected bacterial strains (Massiliasp. andPseudomonassp.) or saprophytic fungus (Clitocybesp.) under controlledin vitroconditions. Inoculation of plants with bacterial strains affected the efficiency of phytoremediation process and was expressed as the quantity of accumulated Cd (Q), the bioaccumulation factor (BCF) and the translocation index (Ti); however, the effect was strain and plant organ specific. The level of hydrogen peroxide (H2O2), which is both an indicator of plant response to biological and/or abiotic environmental stress and a molecule involved in plant-microbial interactions, decreased under the influence of Cd2+in uninoculated plants (plant growth was inhibited by Cd2+) and increased in the inoculated variants of plants growing in the presence of Cd2+(microbiologically stimulated biomass). The saprophytic fungusClitocybesp. generally stimulated biomass and increased the level of H2O2synthesis in all the investigated plant organs and variants of the experiment. We suggest that determination of phytoremediation efficiency, and biochemical response (H2O2) of the host plant underin vitroconditions can help in predicting the final effect of plant-microbial systems in further field trials.

Studies on influence of Cd2+ ions in unidirectional growth and characterization of l-Cysteine hydrochloride monohydrate single crystals

Cadmium doped l-Cysteine hydrochloride monohydrate (Cd2+–C3H7NO2S⋅HCl⋅H2O), a non-linear optical crystal, was grown by conventional as well as unidirectional solution growth techniques. While the dimension of the conventionally grown crystal was 16×14×5mm3, the dimension of the crystal grown unidirectional method was 32mm long and 6mm diameter. The grown crystals were studied using XRD for phase analysis, HRXRD for crystalline perfection and UV–Vis NIR spectroscopy for optical properties. The high crystalline perfection was found in the crystal grown by unidirectional method than that grown by conventional one. FTIR study indicates that Cd2+ ion was coordinated to l-Cysteine⋅HCl⋅H2O through S ligand. The nonlinear optical character of the title compound was observed by measuring the SHG efficiency, which is 1.35times to that of KDP by Kurtz technique.

Influence of Cd2+ ions on the structural, electrical, optical and magnetic properties of Co–Zn nanoferrites prepared by sol gel auto combustion method

Cadmium substituted Co–Zn nanoferrites, Co0.5Zn0.5CdxFe2−xO4 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using the sol–gel auto-combustion method. The powder X-ray diffraction patterns of all the ferrite samples confirmed the formation of single-phase cubic spinel structures having Fd-3m space group. The lattice parameter, ‘a’ increased with increasing Cd2+ ion doping. The d.c resistivity of all the ferrite compositions annealed at 1000°C decreased as the temperature increased, showing their semiconductor nature. However, decrease in resistivity was observed with increasing cadmium concentration. The drift mobility also increased with increasing temperature as well as cadmium concentration because of the enhanced mobility of charge carriers due to thermal activation. The saturation magnetization (Ms), was found to be maximum for the compositional level of Cd having x=0.4, beyond which it decreased due to the spin canting phenomenon. The photo-catalytic degradation was enhanced as the concentration of cadmium ion increased from 0.0 to 1.0.

Single-solute and bi-solute sorption of phenanthrene and dibutyl phthalate by plant- and manure-derived biochars

The spatial arrangement of biochar and the exact underlying interaction mechanisms of biochar and hydrophobic organic compounds both remain largely unknown. The sorption of dibutyl phthalate (DBP) and phenanthrene (PHE) to plant- and manure-derived biochars in both single- and bi-solute systems was investigated. The significant positive relation between surface polarity and ash content suggests that minerals benefit the external distribution of polar groups on particle surfaces. PHE and DBP sorption by the biochars was regulated by their surface polarity. The PHE generally displayed a pronounced enhancement of DBP sorption, likely resulting from the formation of biochar–PHE–DBP complexes, suggesting that DBP and PHE had different sorption sites on the biochars. The enhancement of Cd2+ (a soft Lewis acid) on DBP sorption implied that π–π interactions should not dominate DBP sorption by biochars. The influence of Cd2+ on PHE sorption by biochars would depend on the balance between suppressive sorption by Cd2+PHE bonding and enhanced sorption by Cd2+-complexed functionalities, and the amounts of Cd2+ adsorbed by biochars determined the relative role of increased sorption by Cd2+ in the overall PHE sorption.

Structural and optical properties of CdS/PEO nanocomposite solid films

In this paper solution mixing and casting of Cd(NO3)2·4H2O and poly(ethylene oxide) (PEO) at different molar ratios (1:100–1:600) followed by hydrogen sulfide treatment were employed to fabricate solid films of cadmium sulfide (CdS)/polyethylene oxide (PEO) nanocomposites. The nanocomposites were found to exhibit uniform distribution of CdS nanoparticles in the polymer matrix without any additional capping agent. Systematic investigations on the role of PEO on the optical properties of CdS are presented. The optical properties of the composites examined by UV–vis absorption spectroscopy show that the band gap of CdS nanoparticles increases from 2.45eV to 2.54eV with decreasing concentration of CdS in PEO films. X-ray diffraction pattern shows the broadening in shape of the PEO peaks which is induced by the CdS particles in PEO matrix. The CdS particle sizes ranging from 10 to 20nm are clearly seen in a transmission electron microscope (TEM). The X-ray photoelectron spectroscopic studies (XPS) also confirm the presence of CdS in PEO. Fourier transform infrared spectroscopy studies using attenuated total reflectance (FTIR-ATR) indicate the influence of Cd2+ ion on C–O–C stretching in PEO and confirm the presence of CdS nanoparticles within PEO. Photoluminescence spectroscopy (PL) shows the broad emission due to the presence of surface trapped carrier states.

The influence of Cd2+, Hg2+ and Pb2+ on taxifolin binding to bovine serum albumin by spectroscopic methods: With the viewpoint of toxic ions/drug interference

The effect of heavy metal ions, Cd2+, Hg2+ and Pb2+ on taxifolin binding to bovine serum albumin (BSA) has been investigated by spectroscopic methods. The results indicated that the presence of heavy metal ions significantly affected the binding modes and binding affinities of taxifolin to BSA, and the effects depended on the type of heavy metal ions. One binding mode was found for taxifolin with and without Cd2+, while two binding modes—a weaker one at low concentration and a stronger one at high concentration—were found for taxifolin in the presence of Hg2+ and Pb2+. Cd2+ decreased the binding affinity of taxifolin for BSA by 7.3%; however, Hg2+ increased the binding affinity of taxifolin for BSA by 13.3% in lower concentration and 33.3% in higher concentration. Pb2+ decreased the binding affinity of taxifolin for BSA by 28.4% in lower concentration, and increased the binding affinity of taxifolin for BSA by 20.6% in higher concentration. The decreased binding affinity of taxifolin for BSA in the presence of Cd2+ was mainly because of the existence of competitive binding between taxifolin and Cd2+. However, the conformational change of BSA may the main reason for the changed binding affinity and binding distance of taxifolin for BSA in the presence of Hg2+ and Pb2+.

Presynaptic malfunction: The neurotoxic effects of cadmium and lead on the proton gradient of synaptic vesicles and glutamate transport

Exposure to Cd2+ and Pb2+ has neurotoxic consequences for human health and may cause neurodegeneration. The study focused on the analysis of the presynaptic mechanisms underlying the neurotoxic effects of non-essential heavy metals Cd2+ and Pb2+. It was shown that the preincubation of rat brain nerve terminals with Cd2+ (200μM) or Pb2+ (200μM) resulted in the attenuation of synaptic vesicles acidification, which was assessed by the steady state level of the fluorescence of pH-sensitive dye acridine orange. A decrease in l-[14C]glutamate accumulation in digitonin-permeabilized synaptosomes after the addition of the metals, which reflected lowered l-[14C]glutamate accumulation by synaptic vesicles inside of synaptosomes, may be considered in the support of the above data. Using isolated rat brain synaptic vesicles, it was found that 50μM Cd2+ or Pb2+ caused dissipation of their proton gradient, whereas the application of essential heavy metal Mn2+ did not do it within the range of the concentration of 50–500μM. Thus, synaptic malfunction associated with the influence of Cd2+ and Pb2+ may result from partial dissipation of the synaptic vesicle proton gradient that leads to: (1) a decrease in stimulated exocytosis, which is associated not only with the blockage of voltage-gated Ca2+ channels, but also with incomplete filling of synaptic vesicles; (2) an attenuation of Na+-dependent glutamate uptake.

Influence of Cd2+ on the spin state of non-heme iron and on protein local motions in reactions centers from purple photosynthetic bacterium Rhodospirilium rubrum

Non-heme Fe is a conservative component of the Q-type photosynthetic reaction centers but its function remains unknown. Applying Mössbauer spectroscopy we show that in Rhodospirillum rubrum the non-heme Fe exists mostly in a ferrous low spin state. The binding of Cd2+ ions in the vicinity of the quinone-Fe complex changes the high spin state of the non-heme Fe into a low spin one characterized by hyperfine parameters similar to those obtained for the non-heme Fe low spin state in untreated reaction centers, as confirmed by Mössbauer measurements. The nuclear inelastic scattering of synchrotron radiation experiments show that the contribution of vibrations at low energies, between 3-15 meV, activated at 240 K are damped in the bacterial reaction centers treated with CdCl2. No influence of Cd2+ ions is observed on the soft vibrational states at 60 K. These results suggest that binding of cadmium cations within the reaction centers may enhance decoupling of the non-heme Fe from the surrounding protein matrix at temperatures higher than 200 K, what can explain the slowing down of electron transfer between the QA and QB quinones by Cd2+.

Effect of Cd2+ on the Antioxidant Status of Shizosaccharomyces Pombe

ABSTRACTThe influence of Cd2+ on the antioxidant system of Shizosaccharomyces pombe DSMZ 70576 was studied during batch cultivation on YPD medium containing 1.0 mM Cd(NO3)2 versus a control variant without Cd(NO3)2. The Cd2+ was added to the medium on the 12th h of the process. Samples for determination of the cells' growth, carbon source consumption, ethanol production and antioxidant system's status, represented by the enzymes superoxide dismutase (SOD) and catalase (CAT), and the intracellular principal antioxidant glutathione, were taken along the 48 h cultivation. The presence of 1.0 mM Cd2+ under the test conditions repressed the cell growth and resulted in less production of ethanol. The SOD and CAT specific enzyme activities and glutathione concentration were estimated as 11.8 U mg−1, 1.7 U mg−1 and 0.57 mM mg−1 respectively. The SOD and glutathione values were 1,6 and 1.7 fold higher than the corresponding ones measured during growth without Cd2+, while the CAT activity decreased by 40%. These results indicate that glutathione obviously had scavenged efficiently the H2O2 produced, thus compensated the diminished CAT activity and probably maintained the H2O2 homeostasis of the culture under the stress conditions. Electrophoretical analysis of SOD and CAT in cell free extracts obtained from the strain cultivated in the presence of Cd2+ and in norma indicated the absence of Mn SOD enzyme under the stress conditions. Apparently, the presence of 1.0 mM Cd(NO3)2 leaded to inhibition of mitochondrial functions and Mn SOD operation in the cells of Shizosaccharomyces pombe.

Influence of Cd2+ and Cd(OH)+ Species on Adsorption to Activated Carbons in Aqueous Solutions

Cadmium(II) ions uptake by some chemically different surface activated carbons (ACs) were investigated to find out parameters to optimize the adsorption operation in aqueous solutions. The activated carbons were coal based ACs de-ashed by sequential treatments of HCl and H2F2, the de-ashed AC treated with nitric acid to introduce acidic functional groups on the surface, and contrarily out-gassed at 1000°C in helium flow to eliminate these groups. The pH alternation before and after adsorption revealed that the ion exchange between the Cd2+ species and the surface carboxylic acid was taken place for the oxidized AC, whereas the electrostatic interaction between cadmium(II) ions and Cπ electrons on the graphene layer was valid for AC possessing a little or no C-O complexes. Based on the changes in the shapes of adsorption isotherms for some pH ranges, Cd(OH)+ rather than Cd2+ is considered to be preferable adsorption species onto the acidic oxygen free out-gassed AC surfaces.

The nature of different influence of Cd2+ ions on the conformational equilibrium of triple-stranded polyribonucleotides poly(U)•poly(A)•poly(U) and poly(I)•poly(A)•poly(I) in aqueous solutions

The influence of Cd2+ ions on the conformational equilibrium of single-stranded (poly(U), poly(A), poly(I)) and triple-stranded polyribonucleotides (A2I, A2U) in aqueous solutions (0.1 M Na+ pH 7) has been investigated using difference UV spectroscopy and thermal denaturation. Analysis of the shape and intensity of the DUV spectra of poly(A), poly(I), and A2I has revealed the presence of two types of complex formed as a result of (i) interaction between Cd2+ and the N7 atoms of purines, producing macrochelates; and (ii) binding of Cd2+ to the N1 atoms of poly(A) and poly(I). Since Cd2+ ions are not bound to heteroatoms of the bases in A2U, the conformation of the structure remains stable up to 0.02 M Cd2+. There is a critical Cd2+ concentration (∼1.5•10−4 M) above which A2I assumes a new helical conformation with lower thermal stability. It is supposed that, upon the formation of the “metallized” A2I triplex, the Cd2+ ions are located inside the triple helix and form bridges between the hypoxanthine and adenine of the homopolynucleotide strands.