电絮凝处理酸性矿山废水及响应面优化

通过铁和铝电极材料的对比,选择铝极板作为电极材料,研究极板间距、电流密度、反应时间及废水pH对电絮凝法处理酸性矿山废水的影响。结果表明,当废水中Fe2+、Cu2+和Zn2+的初始质量浓度分别为295.1、18.3、8.2 mg/L时,极板间距10 mm、电流密度20 mA/cm2、废水pH=5.0的条件下,反应40 min后,Fe2+、Cu2+和Zn2+的去除效率分别达到了90.8%、96.5%和96.8%,反应后废水的pH可达到6.7。在单因素试验的基础上,以电絮凝中Fe2+、Cu2+和Zn2+的去除率的最大值,以及出水pH最大值为评价指标,通过响应曲面法建立模型分析拟合得出优化条件并重复3次试验加以验证。结果表明,在电流密度21 mA/cm2、反应时间35 min、极板间距10 mm时,对Fe2+、Cu2+和Zn2+的平均去除率分别为87.02%、93.91%和94.63%,平均pH为6.13,该模型能够较好预测电絮凝对酸性矿山废水的处理效果。絮凝体SEM-EDS检测分析证明Fe、Cu、Zn等重金属可有效从废水中去除。     

Iodine-123 labelled nor-beta-CIT binds to the serotonin transporter in vivo as assessed by biodistribution studies in rats

Flavobacterium aurantiacum NRRL B-184 possesses the ability to degrade aflatoxin B1 in solution and in several food items. Aflatoxin B1 is a potent carcinogen that causes significant economic losses to the agricultural and food industry. The role of trace metal ions (Cu2+, Mn2+, Zn2+, and Co2+) were studied in an effort to understand the enzymatic system involved in aflatoxin B1 degradation by F aurantiacum. The effect of divalent chelators (EDTA and 1,10-phenanthroline [OPT]) in the presence of the trace metal ions was studied as well. Aflatoxin B1 (10 microg/ml) was added to 72-h cultures of F aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). HPLC was used to determine aflatoxin B1 concentration in these cultures. Incubating cells at 30 degrees C with 1 and 10 mM Cu2+, Mn2+, and Zn2+ significantly decreased aflatoxin B degradation after 4 and 24 h (P < 0.05). Decreased degradation was also observed with 1 and 10 mM Cu2+ and Zn2+ after 48 h and with 0.1 mM Cu2+ after 24 and 48 h. Co2+ did not have a significant effect on aflatoxin B1 degradation. EDTA and OPT did not counter the inhibition in the presence of Cu2+. The addition of 1 mM EDTA countered the inhibition by 1 mM Mn2+ after 4 and 24 h, but 1 mM OPT did not counter the inhibition by 10 mM Mn2+ after 4 and 24 h. OPT countered the inhibition by 1 mM Zn2+ after 4 and 48 h. These trace elements inhibit aflatoxin B1 degradation by F aurantiacum. In addition, their presence necessitates higher concentrations (>1 mM) of EDTA and OPT for the removal of their inhibitory effect.     

Removal of Heavy Metal Ions by Waste Biomass of Saccharomyces Cerevisiae

The kinetics, equilibriums, and thermodynamics of metal ion (Pb2+, Ag2+, Cu2+, Zn2+, Co2+, Sr2+, and Cs+) biosorption by the waste yeast cells of Saccharomyces cerevisiae from a local brewery were investigated. The results showed that the biosorption of these metal ions on the biomass was a very rapid process, following the pseudo-second-order equation gave the better fitting results in describing the kinetic data than the pseudo-first-order equation. The equilibrium data could be fitted well with the Langmuir model. The maximum sorption capacity obtained from the Langmuir model followed Pb>Ag>Cu>Zn>Co>Sr>Cs (based on mmol?g?1). The biosorption process by the yeast was favorable for these metal ions removal according to the constant separation factor (0相似文献   

Solution structure of methionine-oxidized amyloid beta-peptide (1-40). Does oxidation affect conformational switching?

The solution structure of Abeta(1-40)Met(O), the methionine-oxidized form of amyloid beta-peptide Abeta(1-40), has been investigated by CD and NMR spectroscopy. Oxidation of Met35 may have implications in the aetiology of Alzheimer's disease. Circular dichroism experiments showed that whereas Abeta(1-40) and Abeta(1-40)Met(O) both adopt essentially random coil structures in water (pH 4) at micromolar concentrations, the former aggregates within several days while the latter is stable for at least 7 days under these conditions. This remarkable difference led us to determine the solution structure of Abeta(1-40)Met(O) using 1H NMR spectroscopy. In a water-SDS micelle medium needed to solubilize both peptides at the millimolar concentrations required to measure NMR spectra, chemical shift and NOE data for Abeta(1-40)Met(O) strongly suggest the presence of a helical region between residues 16 and 24. This is supported by slow H-D exchange of amide protons in this region and by structure calculations using simulated annealing with the program XPLOR. The remainder of the structure is relatively disordered. Our previously reported NMR data for Abeta(1-40) in the same solvent shows that helices are present over residues 15-24 (helix 1) and 28-36 (helix 2). Oxidation of Met35 thus causes a local and selective disruption of helix 2. In addition to this helix-coil rearrangement in aqueous micelles, the CD data show that oxidation inhibits a coil-to-beta-sheet transition in water. These significant structural rearrangements in the C-terminal region of Abeta may be important clues to the chemistry and biology of Abeta(1-40) and Abeta(1-42).     

Growth factor release from amylopectin hydrogel based on copper coordination

This paper describes a biodegradable hydrogel matrix releasing basic fibroblast growth factor (bFGF) on the basis of protein metal coordination with the protein drug. The biodegradable hydrogel was prepared from amylopectin by its crosslinking with ethylene glycol diglycidyl ether, followed by introduction of diethylenetriaminepentaacetic acid (DTPA) residues for copper chelation. When bFGF was incorporated into the DTPA-introduced amylopectin hydrogel after chelation with Cu2+, an insignificant amount of bFGF was released from the hydrogel in buffered solution, in contrast to that without Cu2+ chelation. An increased ionic strength in the solution did not affect the bFGF release, indicating the occurrence of coordinate bonding of bFGF to the DTPA-introduced hydrogel through Cu2+ chelation. An implantation study with 125I-labeled amylopectin hydrogels demonstrated that they underwent degradation in the back subcutis of mice. Cu2+ chelation of hydrogels enabled bFGF to remain in the mouse back for a long time period, irrespective of DTPA introduction. However, DTPA residues were necessary to induce significant neovascularization by the Cu2+-chelating hydrogels incorporating bFGF. The DTPA-introduced amylopectin prevented Cu2+-induced deactivation of bFGF, again in marked contrast to DTPA-free amylopectin. It was concluded that biologically active bFGF could be incorporated to DTPA-introduced amylopectin through Cu2+ chelation in a stabilized state and was released as a result of hydrogel biodegradation, resulting in prolonged neovascularization.     

Sunlight mutagenesis: changes in mutational specificity during the irradiation of phage M13mp2

BACKGROUND: The accumulation of fibrillar deposits of amyloid beta-peptide (Abeta) in brain parenchyma and cerebromeningeal blood vessels is a key step in the pathogenesis of Alzheimer's disease. In this report, polymerization of Abeta was studied using fluorescence correlation spectroscopy (FCS), a technique capable of detecting small molecules and large aggregates simultaneously in solution. RESULTS: The polymerization of Abeta dissolved in Tris-buffered saline, pH 7.4, occurred above a critical concentration of 50 microM and proceeded from monomers/dimers into two discrete populations of large aggregates, without any detectable amount of oligomers. The aggregation showed very high cooperativity and reached a maximum after 40 min, followed by an increase in the amount of monomers/dimers and a decrease in the size of the large aggregates. Electron micrographs of samples prepared at the time for maximum aggregation showed a mixture of an amorphous network and short diffuse fibrils, whereas only mature amyloid fibrils were detected after one day of incubation. The aggregation was reduced when Abeta was incubated in the presence of Abeta ligands, oligopeptides previously shown to inhibit fibril formation, and aggregates were partly dissociated after the addition of the ligands. CONCLUSIONS: The polymerization of Abeta is a highly cooperative process in which the formation of very large aggregates precedes the formation of fibrils. The entire process can be inhibited and, at least in early stages, partly reversed by Abeta ligands.     

Heparin-binding properties of the amyloidogenic peptides Abeta and amylin. Dependence on aggregation state and inhibition by Congo red

Aggregation and deposition of the 40-42-residue amyloid beta-protein (Abeta) are early and necessary neuropathological events in Alzheimer's disease. An understanding of the molecular interactions that trigger these events is important for therapeutic strategies aimed at blocking Abeta plaque formation at the earliest stages. Heparan sulfate proteoglycans may play a fundamental role since they are invariably associated with Abeta and other amyloid deposits at all stages. However, the nature of the Abeta-heparan sulfate proteoglycan binding has been difficult to elucidate because of the strong tendency of Abeta to self-aggregate. Affinity co-electrophoresis can measure the binding of proteoglycans or glycosaminoglycans to proteins without altering the physical state of the protein during the assay. We used affinity co-electrophoresis to study the interaction between Abeta and the glycosaminoglycan heparin and found that the aggregation state of Abeta governs its heparin-binding properties: heparin binds to fibrillar but not nonfibrillar Abeta. The amyloid binding dye, Congo red, inhibited the interaction in a specific and dose-dependent manner. The "Dutch" mutant AbetaE22Q peptide formed fibrils more readily than wild type Abeta and it also attained a heparin-binding state more readily, but, once formed, mutant and wild type fibrils bound heparin with similar affinities. The heparin-binding ability of aggregated AbetaE22Q was reversible with incubation in a solvent that promotes alpha-helical conformation, further suggesting that conformation of the peptide is important. Studies with another human amyloidogenic protein, amylin, suggested that its heparin-binding properties were also dependent on aggregation state. These results demonstrate the dependence of the Abeta-heparin interaction on the conformation and aggregation state of Abeta rather than primary sequence alone, and suggest methods of interfering with this association.     

Numerical Simulation of Transport of Four Heavy Metals in Kaolinite Clay

A multicomponent reactive solute-transport model was used to study the migration of dissolved heavy metals (Cd2+, Pb2+, Cu2+, and Zn2+) in a clay barrier subject to two leachates having different pH values. This solute-transport model is capable of simulating simultaneous processes of water flow, advective-dispersive-solute transport, and chemical reactions. The migration of these metals was simulated in a kaolinite landfill liner, which was assigned realistic physical and chemical properties and boundary conditions to model one-dimensional contaminant transport. The leachate input properties to the model were those of an actual leachate containing the four heavy metals. The numerical simulations were focused on the concentration profiles of these metals in the simulated clay barrier and leachate pH affects their mobilities. The numerical results indicate that with a nearly neutral leachate, the heavy metals mobility follows: Cd2+ < Pb2+ < Cu2+ < Zn2+. With an acidic leachate, the order changes to Pb2+ < Cu2+ < Zn2+ < Cd2+. Leachate pH has a significant effect on Cd2+ and Pb2+ mobility and a small effect on Cu2+ and Zn2+.     

M(Ⅱ)-S-H2O体系的热力学平衡

根据配位化学热力学平衡原理,绘制了298.15 K时S-H₂O系含硫物种的离子分率α_n-pH图,以及4种重金属离子(Cu、Pb、Zn、Cd)-S-H₂O体系的硫化平衡pM-pH图.α_n-pH图指出了不同pH值下水溶液中硫的存在形式,当pH>12.5时,溶液中逐渐出现S2-,pH值达到16以上时,溶液中的S主要以S2-的形式存在,其离子分率达到了98.61 %.pM-pH图指出了4种重金属硫化物在溶解平衡时,总离子浓度与pH值的关系.pH值分别在7.75、8.87、8.36、9.83时,CuS、PbS、ZnS、CdS的溶解度最小.同时对热力学计算结果进行了实验验证,结果表明:在一定的金属浓度下,pH值分别为8.2、8.7、8.3、10.3时,溶液中金属离子浓度达到最小值,基本符合热力学分析结果.这些热力学研究具有较高的实用价值,为硫化沉淀法处理重金属废水提供了理论依据.      

Influence of treatment with aminoglutethimide on plasma and red-blood-cell glutathione status in breast cancer patients

Using the method of differential scanning calorimetry, the DNA helix-coil transition was studied in solutions (10(-3) M Na+, 10(-3) M tris HCl, pH 7.0) containing divalent copper ions at relative metal ion concentrations (Mt2+/PDNA) ranging from 0.2 to 20. Dependences of the melting temperature and enthalpy on relative ion concentration were determined. An aggregation of Cu(2+) + DNA complexes in the range of average ion concentration was established. It is shown that the melting enthalpy of "units" increases with copper ion concentration. The data obtained were compared with values determined by UV-spectroscopy. Association constants for Cu2+ binding to DNA were defined by the ligand theory.     

P204+P507对钴浸出液协同萃取除钙锰铜锌

针对分步萃取法萃取钴工艺流程繁杂、萃取级数较多的问题,采用P204+P507为复配萃取剂从工业硫酸钴浸出液中一次分离出Zn2+、Ca2+、Mn2+、Cu2+等。探究了平衡pH、复配萃取剂配比、萃取相比O/A、有机相皂化率等对元素萃取率的影响。结果表明：以28%P204+7%P507为复配萃取剂,65%溶剂油为稀释剂,在有机相皂化率为50%、萃取平衡pH=3.57、相比O/A=2的条件下,Zn2+、Ca2+、Mn2+、Cu2+的单级萃取率分别达到99.97%、94.65%、88.42%、87.18%,Co2+萃取率仅有17.42%。后续使用1.5 mol/L硫酸在反萃相比O/A=20、两次洗涤条件下可以将99%的钴洗涤下来。     

Modulation of metal-induced genotoxicity by Maillard reaction products isolated from coffee

PM2 bacteriophage DNA was exposed to non-dialysable Maillard reaction products (MRPs) isolated from brewed (Br), boiled (Bo) and instant (I) coffee brew extracts in a Fe2+ catalysed Fenton reaction at four pH conditions (i.e. 7.5, 4.0, 3.2, 2.6). MRPs were incubated with DNA either directly with Fe2+, or following a short preincubation period conducted with Fe2+ in an atmosphere of oxygen or argon. Damage to supercoiled DNA resulting in strand scissions as characterized by both nicked circular and linear forms were found to occur either with coffee MRPs or Fe2+ alone, in a dose-dependent manner at all pH conditions tested. At low MRP concentrations, damage to DNA with respect to Fe2+ was lowered only when MRPs were preincubated with Fe2+ in argon or oxygen before incubating with DNA. The addition of MRPs and Fe2+ to DNA without preincubation, had no effects in protecting DNA damage. This finding showed that a preincubation step is necessary for MRPs to chelate Fe2+ in order to mitigate the Fenton reaction. In contrast, the protective effects against Fe2+-induced DNA breakage by MRPs were lost at high coffee MRP concentrations, irrespective of the incubation method used. Increasingly higher concentrations of MRPs in combination with Fe2+ actually enhanced the breakage of DNA with respect to the control. These results indicate that MRPs at high concentrations do not improve Fe2+ ion chelation, but rather accelerate the DNA breakage by possibly changing the redox state of the transition element.     

吸附材料处理含Zn2+重金属废水的影响因素

考察了废水初始pH值、不同阳离子、阴离子、有机物、共存重金属离子、极端条件等因素对吸附Zn2的影响.结果表明,8h后吸附接近饱和,废水初始pH =6时处理效果最好,Zn2+吸附容量为3.98 mg/g,去除率为79.6％;Na+、K+、Mg2+、Ca2+均会抑制Zn2的吸附,影响顺序从小到大为Na+＜K+＜ Mg2+＜ Ca2+;Cl-、SO2-4对吸附Zn2+抑制作用很小,且Cl-的抑制作用小于SO2-4;COD对吸附Zn2+有促进作用;Pb2+、Cu2+共存时,对Zn2+的吸附有抑制作用,影响顺序为Pb2+单元体系＜ Cu2+单元体系＜ Pb2+、Cu2+二元体系;高盐和强酸对Zn2+的吸附有较大影响,但高温基本无影响.饱和吸附材料的后处理试验表明,在550℃马弗炉中热处理6.5h,烧失率为75.4％,烧渣中Zn2+含量为1.75％,与热处理前相比,富集倍数为4.1倍.本文研究成果为吸附法处理含锌重金属废水并回收废水中的重金属提供了重要依据.     

Identification and characterization of a protease produced by Vibrio parahaemolyticus in iron-limited medium

Two proteolytic proteins (about 43 and 90 kDa) were produced by clinical strains of Vibrio parahaemolyticus cultured in iron-limited medium. The 43 kDa-protease was partially purified by ammonium sulfate precipitation, ultrafiltration fractionation and DEAE-Sephacel chromatography. This protease had an optimum pH range of 7 to 8, and an optimum reaction temperature of about 40 degrees C. It was heat-labile, being partially inactivated by heat-treatment at 60 or 90 degrees C for 10 min. The protease hydrolyzed casein, gelatin, elastin, collagen and hemoglobin. As a chymotrypsin-like protease, it was inhibited only by the chymostatin among seven protease inhibitors tested. Activity of this protease was partially inhibited by 1 mM of Co2+, Cu2+, Zn2+ and Hg2+ and slightly enhanced by Ca2+ and Ba2+. It was completely inactivated by orthophenanthroline (OPA), and the OPA-inactivated sample was partially reactivated by Ca2+ and Fe2+. In conclusion, this 43-kDa protease of V. parahaemolyticus was an unstable neutral chymotrypsin-like metalloprotease; Ca2+ and/or Fe2+ was essential for its activity or stability.     

Amyloid beta-peptide is transported on lipoproteins and albumin in human plasma

The amyloid beta-peptide (Abeta) is the major constituent of neuritic plaques in Alzheimer's disease and occurs as a soluble 40-42-residue peptide in cerebrospinal fluid and blood of both normal and AD subjects. It is unclear whether Abeta, once it is secreted by cells, remains free in biological fluids or is associated with other proteins and thus transported and metabolized with them. Such knowledge of the normal fate of Abeta is a prerequisite for understanding the changes that may lead to the pathological aggregation of soluble Abeta in vivo, the possible influence of certain extracellular proteins, particularly apolipoprotein E, on plaque formation, and the pharmacology of putative Abeta-lowering drugs. To address the question of Abeta distribution in human biological fluids, we incubated fresh human plasma from 38 subjects with physiological concentrations (0.5-0.7 nM) of radioiodinated Abeta1-40 and seven plasma samples with Abeta1-42. Lipoproteins and lipid-free proteins were separated and analyzed for bound iodinated Abeta1-40. We found that up to 5% of Abeta added to plasma is bound to selected lipoproteins: very low density, low density, and high density, but not lipoprotein(a). The large majority ( approximately 89%), however, is bound to albumin, and very little Abeta is free. Abeta distribution in plasma was not significantly influenced by apolipoprotein E genotype. We conclude that Abeta is normally bound to and transported by albumin and specific lipoproteins in human plasma under physiological conditions.     

Calcium ion binding to thrombospondin 1

We have quantified the binding of Ca2+ to platelet thrombospondin 1 (TSP1) using equilibrium dialysis with 45CaCl2. Ca2+ binding to TSP1 was found to be cooperative with 10% occupancy at 15-20 microM CaCl2, 90% occupancy at 100 microM CaCl2, and a Hill coefficient of 2.4 +/- 0.2 The average apparent Kd was 52 +/- 5 microM. Maximum binding, assuming Mr = 450,000 and epsilon = 0.918 (A280/mg/ml), was 35 +/- 3 Ca2+/TSP1. This value is close to the 33 sites (11 per subunit) predicted based on homology of the epidermal growth factor (1 site) and aspartate-rich (10 sites) regions to known Ca2+ binding sequences. Ca2+ protected the aspartate-rich region from trypsin proteolysis, but not until nearly all of the Ca2+ binding sites were filled. At lower occupancy of Ca2+ binding sites, several limited tryptic digest products were obtained. This finding and the previous demonstration of extensive thiol-disulfide isomerization within the aspartate-rich regions suggest that subregions of the aspartate-rich region are stabilized in different conformers. Zn2+, Cu2+, Mn2+, Mg2+, Co2+, Cd2+, and Ba2+ were tested for their ability to modulate Ca2+ binding and protease sensitivity of TSP1. Zn2+ inhibited 40% of the Ca2+ binding but neither protected TSP1 from trypsin proteolysis, nor labilized TSP1 toward trypsin proteolysis. These results provide direct evidence for high capacity, cooperative and specific binding of Ca2+ to conformationally labile aspartate-rich repeats of TSP1.     

Inhibition studies of the carnitine acetyltransferase from skeletal muscle of the camel (Camelus dromedarius) by sulfhydryl reagents and metal ions

The effect of certain sulfhydryl reagents and metal ions were studied on the carnitine acetyltransferase (CAT) activity from the skeletal muscle of the Arabian camel (Camelus dromedarius). DTNB and iodoacetamide caused concentration and time dependent inhibition of CAT activity. The inhibition seen with these sulfhydryl reagents could be protected with prior incubation of the enzyme with acetyl-Co A, suggesting that these reagents might interact with the same site. Among the various metal ions tested, Cu2+, Zn2+ and Hg2+ caused total inhibition at very low concentrations, while, Mn2+, Mo6+ and Co2+ caused between 32-52% inhibition at 10 mM concentrations. Alkali earth divalent metals Mg2+ and Ca2+ caused less than 15% inhibition at this concentration. These metal ions are probably interacting at certain nucleophilic groups in the enzyme thus disrupting its tertiary structure.     

Micromechanical properties of epiphyseal trabecular bone and primary spongiosa around the physis: an in situ nanoindentation study

The application of amyloid beta-peptide (Abeta) 1-40 (10 microM) caused neurodegeneration of hippocampal neuronal cells, as indicated by the release of lactate dehydrogenase (LDH) into the culture medium. Treatment with idebenone (10-1000 nM), a potent antioxidant in mitochondria, protected the hippocampal neurons against the Abeta1-40(10 microM)-induced neurotoxicity. To determine the morphological change in neurons during the Abeta1-40-induced cytotoxicity, the cells were immunostained with anti-MAP2 antibodies. After 4-day exposure to 10 microM Abeta1-40, the number of neurons was reduced, and the surviving neurons had an apparently reduced number of neurites which were shorter than those of control neurons. When idebenone was added to the culture medium with Abeta1-40, the number of surviving neurons was significantly increased, and their neurites were as long as seen in control culture. These results suggest that reactive oxygen species mediate neurotoxicity of Abeta1-40, and idebenone protects neurons against the Abeta1-40-induced neurotoxicity.     

Inhibition of Alzheimer beta-fibrillogenesis by melatonin

It is generally postulated that the amyloid beta protein (Abeta) plays a central role in the progressive neurodegeneration observed in Alzheimer's disease. Important pathologic properties of this protein, such as neurotoxicity and resistance to proteolytic degradation, depend on the ability of Abeta to form beta-sheet structures or amyloid fibrils. We report that melatonin, a hormone recently found to protect neurons against Abeta toxicity, interacts with Abeta1-40 and Abeta1-42 and inhibits the progressive formation of beta-sheets and amyloid fibrils. These interactions between melatonin and the amyloid peptides were demonstrated by circular dichroism and electron microscopy for Abeta1-40 and Abeta1-42 and by nuclear magnetic resonance spectroscopy for Abeta1-40. Inhibition of beta-sheets and fibrils could not be accomplished in control experiments when a free radical scavenger or a melatonin analog were substituted for melatonin under otherwise identical conditions. In sharp contrast with conventional anti-oxidants and available anti-amyloidogenic compounds, melatonin crosses the blood-brain barrier, is relatively devoid of toxicity, and constitutes a potential new therapeutic agent in Alzheimer's disease.