Stability of Ca2+-, Cd2+-, Cu2+-[illite-humic] complexes and pH influence

Decomposition of fresh plant residues in soil is expected to produce humic fractions varying in molecular size. It was hypothesized that metal adsorption by soil, to some degree, will depend on humic acid content and molecular size. The latter is expected to vary in number and type of functional groups. In this study, illite-humic complexes were used to evaluate Ca²⁺, Cd²⁺, and Cu²⁺ adsorption and how this adsorption was affected by humic acids, differing in molecular size, under various pH values. Potentiometric titration using ion-selective electrodes with a stop-and-go procedure was employed to evaluate metal-[illite-humic] complex formation. The results showed that illite-humic complexes exhibited at least two types of metal-ion adsorption sites (low and high affinity) and molecular size of humic fractions had a large potential influence on total metal adsorption but a relatively smaller influence on metal-complex stability. Relative strength of metal-ion-[illite-humic] complexes followed the order of Cu²⁺>Cd²⁺>Ca²⁺ and were affected by pH, especially for low metal-ion affinity sites. Magnitude of metal-[illite-humic] stability constants, depending on molecular size of humic fraction and pH, varied on a log-scale from 3.52 to 4.21 for Ca²⁺, 4.38 to 5.18 for Cd²⁺and from 5.23 to 5.83 for Cu²⁺. There was an approximate 5-fold difference in these stability constants between the three different sizes of humic fractions. The larger the humic fraction, the lower the metal-[illite-humic] stability constant. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Bt毒素在三种矿物表面的吸附与解吸

研究了Bt库斯塔克亚种(kurstaki）毒素（65 kDa）在高岭土、针铁矿和氧化硅表面的吸附和解吸特性.结果表明：在磷酸盐缓冲体系（pH 8）中,3种矿物的等温吸附曲线均符合Langmuir方程（R²>0.9661）,它们对Bt毒素的吸附顺序为：针铁矿﹥高岭土﹥二氧化硅.矿物对Bt毒素的吸附1 h就基本达到了吸附平衡.在pH 6～8范围内,针铁矿、高岭土和二氧化硅对Bt毒素的吸附量随pH值的升高而降低.10 ℃～50 ℃范围内,针铁矿和氧化硅对Bt毒素吸附量随温度升高有所下降（8.39％和47.06％）,高岭土对Bt毒素吸附则略有升高（5.91％）.红外光谱分析显示,Bt毒素被矿物吸附后结构仅有微小变化.被矿物吸附的Bt毒素不易被去离子水解吸,水洗3次总解吸率为28.48%～42.04%.     

Effects of la on surface charges, dielectrophoresis, and electrofusion of barley protoplasts

When dielectrophoresis and electrofusion of barley (Hordeum vulgare var Moor) leaf protoplasts were assayed in the presence of 0.1 to 1 millimolar lanthanum ion (La³⁺) in the basal medium (0.7 molar mannitol, 1 millimolar piperazine-N, N-bis[2-ethanesulfonic acid]-Na [pH 6.7], 0.1 millimolar CaCl₂), dielectrophoresis and induction of electrofusion were strongly inhibited. The latter remained inhibited and the former recovered by about 60% after washing the La³⁺ -treated protoplasts without EDTA. These inhibitions were almost completely abolished by washing the La³⁺ -treated protoplasts with 1 millimolar EDTA. Inductively coupled plasma atomic emission spectroscopic analysis revealed that protoplasts retained a considerable amount of La³⁺ after washing without EDTA and released most of the bound La³⁺ by washing with 1 millimolar EDTA. This tightly bound La³⁺ seemed responsible for the inhibition of electrofusion and dielectrophoresis that was observed in the La³⁺ -treated protoplasts after washing. ζ-potentials of protoplasts were -39.0±3.2 millivolts, -16.7 ± 2.6 millivolts, and virtually zero in media containing 0, 0.1, and 0.3 millimolar La³⁺ (I = 7.2 millimolar), respectively, and had a positive value (+ 14.2 ± 2.2 millivolts) in the presence of 1 millimolar La³⁺. These effects of La³⁺ on ζ-potentials were easily abolished by washing without EDTA. This indicates that charged species located at the surface of plasma membrane of protoplasts cannot account for the sites at which La³⁺ exerts its inhibition of dielectrophoresis and electrofusion. In contrast, the promotion of spherical fusion and the reduction of broken fusion products observed in the presence of La³⁺ were almost completely abolished by washing without EDTA. Our results also indicate that the initial induction and development of electrofusion can be studied independently.     

Initiation of DNA synthesis in quiescent Swiss 3T3 and 3T6 cells by lanthanum

La³⁺ stimulated quiescent Swiss 3T3 and 3T6 ceils to enter the DNA-synthesizing S phase of the cell cycle. La³⁺ and insulin interacted synergistically to increase DNA synthesis. A brief exposure of the cells to soluble LaCl₃ optimally stimulated entry into S. La³⁺ was similar to Al³⁺ in its mitogenic properties (J. Cell. Physiol.118 , 298, 1984), but La³⁺ was 10 times more potent than Al³⁺.     

草酸对土壤胶体与矿物表面酶的吸附及活性影响

采用平衡批处理法,研究了模拟根系分泌物--草酸溶液的浓度、pH对酸性磷酸酶在针铁矿、高岭石及黄棕壤和砖红壤胶体(＜2μm)上的吸附及比活的影响.结果表明,针铁矿对磷酸酶的吸附量受草酸浓度的影响较小,其它供试胶体对蛋白的吸附量随草酸浓度的升高,一般表现为先急剧降低(0～5mmol·L^-1),之后逐渐升高到与对照相当或略低.这与草酸在土壤胶体和矿物表面的配位形态及其对载体表面的电荷改变、溶解有关.草酸体系中,供试胶体对磷酸酶的吸附顺序为针铁矿>黄棕壤＞高岭石＞砖红壤.酶在草酸体系中的最大吸附点位一般出现在蛋白的等电点(IEP)和供试胶体的PZC之间,而酶在草酸体系中被固定到供试胶体上之后,其最适比活点随胶体类型的不同而没有变化或有所高移.     

Adsorption and anti-ultraviolet light characteristics of the protoxin from Bacillus thuringiensis on montmorillonite,kaolinite, zinc oxide and rectorite

The adsorption, desorption and anti-ultraviolet light characteristics of the protoxin from Bacillus thuringiensis strain WG-001 on montmorillonite, kaolinite, zinc oxide and rectorite were studied. The protoxin was easily adsorbed onto minerals and the adsorption reached equilibrium within 0.5–1.0 h (except for rectorite). The adsorption isotherms of protoxin at different concentrations in sodium carbonate buffer (pH 9) followed the Langmuir (R ² >0.97) and Freundlich (R ² >0.95) equations. The maximum amounts of protoxin adsorbed were in the order: montmorillonite>rectorite>znic oxide>kaolinite. In the range of pH from 9 to 11 (carbonate buffer), the protoxin adsorbed decreased with increasing pH. The adsorption was not significantly affected by the temperature between 5 and 45°C. Both free and adsorbed protoxin were toxic to larvae of Heliothis armigera. The LC₅₀ value of free and adsorbed protoxin on montmorillonite, rectorite, zinc oxide and kaolinite were 14±1.16, 1.76±0.31, 2.94±0.71, 4.78±2.08 and 1.91±0.91 µg mL^?1, respectively. After 1 h of ultraviolet irradiation, the LC₅₀ of the above samples increased by 41.4, 19.3, 16.3, 125.9 and 62.3%, respectively. The desorption of adsorbed protoxin in water ranged from 30.1 to 64.9% and from 18.5 to 48.7% in carbonate buffer.     

Methacryloylamidohistidine in affinity ligands for immobilized metal-ion affinity chromatography of ferritin

A new metal-chelate adsorbent utilizing 2-methacryloylamidohistidine (MAH) was prepared as a metalchelating ligand. MAH was synthesized using methacryloly chloride and histidine. Monosize nanospheres with an average diameter of 450 nm were produced by emulsion polymerization of 2-hydroxyetylmethacrylate (HEMA) and MAH. Then, Fe³⁺ ions were chelated directly onto the monosize nanospheres. Mon-poly(HEMA-MAH) nanospheres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and elemental analysis. Fe³⁺ chelated monosize nanospheres were used in ferritin adsorption from an aqueous solution. The maximum ferritin adsorption capacity of Fe³⁺-chelated mon-poly(HEMAMAH) nanospheres was 202 mg/g at pH 4.0 in acetate buffer. The non-specific ferritin adsorption on the monpoly( HEMA-MAH) nanospheres was 20 mg/g. The adsorption behavior of ferritin could be modeled using both Langmuir and Freundlich isotherms. The adsorption capacity decreased with increasing ionic strength of the binding buffer. High desorption ratios (> 95% of the adsorbed ferritin) were achieved with 1.0 M NaCl at pH 7.0. Ferritin could be repeatedly adsorbed and desorbed with the Fe³⁺-chelated mon-poly(HEMA-MAH) nanospheres without significant loss of adsorption capacity.     

Influence of lanthanum on the uptake of trace elements in cucumber plant

The effects of La³⁺ on the uptake of trace elements (Se, Co, V, and Tc) in cucumber plants were studied by a radioactive multitracer technique. It was observed that the uptake and distribution of these trace elements in roots, stems, and leaves are different under different La³⁺ treatments. Furthermore, in the control, the plant accumulates ⁷⁵Se, ⁵⁶Co, and ⁴⁸V all in the order roots>leaves>stems, whereas ^95mTc was in the order leaves>stems>roots. The accumulations of ⁷⁵Se and ^95mTc in plants treated with different La³⁺ concentration were in the same order as those in the control, but the uptakes percentages of other kinds of element changed differently. The results indicate that lanthanum treatments to a growing cucumber lead to the change of uptake of trace elements, which suggest that a rare earth element is directly or indirectly involved in the ion transport of the plant and affects plant growth by regulating the uptake and distribution of elements that influence the plant cell physiology and biochemistry.     

Effects of Temperature,pH and Salt Concentrations on the Adsorption of Bacillus subtilis on Soil Clay Minerals Investigated by Microcalorimetry

Adsorption of microorganisms on minerals is a ubiquitous interfacial phenomenon in soil. Knowledge of the extent and mechanisms of bacterial adsorption on minerals is of great agronomic and environmental importance. This study examined adsorption of Bacillus subtilis on three common minerals in soils such as kaolinite, montmorillonite and goethite under various environmental conditions. Isothermal titration calorimetry (ITC) was used to investigate the effects of temperature (20, 30, and 40°C), pH (5.0, 7.0, and 9.0) and KNO₃ concentration (0.001, 0.01, and 0.1 mol L^?1) on the adsorption by direct measurement of enthalpies. The results revealed that the adsorption process in all the mineral systems were exothermic, with the enthalpy changes (ΔH_ads ) ranging from ?52 to ?137, ?33 to ?147, and ?53 to ?141 kJ kg^?1 (dry weight of adsorbed bacteria) for kaolinite, montmorillonite, and goethite, respectively. No obvious dependence of ΔH_ads on temperature was observed. The heat release for all the systems generally declined with pH and decrease of salt concentration, which can be explained by the variations of hydrophobicity and electrostatic force with pH or salt concentration. The largest decrease was found for goethite among the three minerals from pH 5.0 to 7.0, suggesting that electrostatic attraction may play a more important role in bacterial adsorption on this mineral. The ΔH_ads values for all the minerals became nearly the same at pH 9.0, indicating that the same force probably hydrophobicity governing the adsorption for the minerals in alkaline environment. It is assumed that acidic or saline soils and the associated environments favor the adsorption of B. subtilis on clay minerals. In addition, the negative enthalpies expressed as kJ kg^?1 (carbon) revealed an energy flow into the environment accompanied by the carbon adsorption on the minerals in soil.     

Use of lanthanum to accurately quantify insulin-like growth factor binding to proteins on cell surfaces

Insulin-like growth factor binding proteins (IGFBPs) are found both associated with cells and in extracellular fluids. Cell-associated IGFBPs increase [¹²⁵I]-IGF binding to cell monolayers, whereas extracellular (soluble, released) IGFBPs decrease binding. In the current study, we show that either IGFBP-3 or IGFBP-5 are the major forms of IGFBP released from monolayers of human GM10 fibroblasts, T98G glioblastoma cells and forskolin-treated bovine MDBK cells. IGFBPs represent the most abundant [¹²⁵I]-IGF-I binding site on GM10 and T98G cell monolayers, but 4-17% of the total cell-associated IGFBPs are released from the cell monolayer at 8°C during their quantification. Most of the IGFBPs (> 70%) are released from MDBK cells. Quantitative estimates of [¹²⁵I]-IGF binding to the cell monolayers are altered because of the ability of the released IGFBPs to reduce the amount of radiolabeled ligand that is available to bind to the cell surface. Lanthanum (La³⁺) depresses IGFBP release from all three cell types (> 80% for GM10 and T98G cells and > 65% for MDBK cells). The effect was cation specific, noted with La³⁺ or Zn²⁺ but not with either Mn²⁺, Sr²⁺ or Se³⁺. The effect was also IGFBP specific; La³⁺ markedly depressed the release of IGFBP-3 and IGFBP-5, but had less of an effect on IGFBP-2 and IGFBP-4. Concomitant with a decrease in IGFBP-3 and IGFBP-5 release, La³⁺ caused an increase in [¹²⁵I]-IGF-I binding to cell-associated IGFBPs and type I IGF receptors. The released soluble IGFBPs have a three- to 20-fold greater affinity (K_a) for [¹²⁵I]-IGF-I compared to cell-associated IGFBPs. La³⁺ did not alter the affinity constants of cell-associated IGFBPs. In summary, we have identified a means to prevent loss of IGFBPs from cell monolayers during binding assays. This procedure will be useful in accurately quantifying the levels of IGFBPs on cell monolayers and in determining the role of cell-associated IGFBPs in controlling IGF activity. Retention of cell-associated low affinity IGFBPs may be important in controlling the size of the pericellular IGF pool and in regulating IGF-I access to the type I IGF receptor. J. Cell. Biochem. 66:256-267. © 1997 Wiley-Liss, Inc.     

Adsorption of Copper and Cadmium by Cu- and Cd-Resistant Bacteria and Their Composites with Soil Colloids and Kaolinite

Abstract

Remediation of toxic metals by bacteria offers a relatively inexpensive and efficient way for the decontamination of soil and associated environments. The present study was carried out to investigate the surface characteristics, adsorption, and remobilization of Cd and Cu on bacteria and their composites with soil colloidal components, which are the most active constituents in soils. The bacterial strain NTG-01 (Enterobacter aerogenes), which was both Cd- and Cu-resistant, was isolated from a heavily Cu-contaminated soil of the mining area in Daye suburb of Hubei Province, China. Batch laboratory experiments with NTG-01 and soil colloids were performed to quantify adsorption of Cu and Cd. The surface area of kaolinite and the soil colloids from an Alfisol and Ultisol increased by 3.0–8.8% after the introduction of the bacteria. In the presence of bacterial cells, the negative charges of soil colloid systems increased and the positive charges decreased, shifting pH from 4.0 to 6.5. Our results demonstrate that bacteria promote the adsorption of Cd and Cu by kaolinite and soil colloid systems. However, the heavy metals bound by the bacterial composites could also be easily released by NH₄NO₃ and EDTA. Caution should be taken when using such bacterial strains in bioremediation of heavy metal-contaminated soils.     

Rapid growth responses of Avena coleoptile segments to lanthanum and other cations

The rapid growth responses of oat (var. Victory) coleoptile segments treated with millimolar concentrations of the chlorides of La³⁺, Ca²⁺, K⁺, and NH₄⁺, respectively, have been measured. La³⁺ and Ca²⁺ initially depressed the endogenous elongation rate. In the case of La³⁺ a prolonged stimulatory effect on the rate of elongation was produced by concentrations of 50 millimolar down to 20 micromolar after an initial depression of elongation rate. The effect of K⁺ was slightly stimulatory and showed a synergistic effect in combination with La³⁺. NH₄⁺ produced an immediate rapid increase in elongation rate. La³⁺ did not behave as a “super calcium” in its action upon the spontaneous growth response. The prolonged elongation of the La³⁺-treated segments exhibiting the spontaneous growth response is apparently a newly observed effect. These rapid growth responses are interpreted as an interaction between anionic lipid-protein complexes in the plasmalemma and the respective ions.     

Effect of lanthanum on ion absorption in cucumber seedling leaves

Scanning electron microscope and energy-dispersive X-ray analysis were used to study the tissular distributions of elements Na, Mg, Cl, K, Ca, Mn, and Fe in leaves of cucumber seedlings in the absence or presence of La³⁺. The results showed that the atomic percentages of Na, Mg, Cl, K, and Ca were basically reduced and those of Mn and Fe were increased in the presence of La³⁺; in addition, at 0.02 mM La³⁺, the reduced or increased degrees were higher than those at 2.0 mM La³⁺. The effects of La³⁺ on ion absorption were similar to those of Ca²⁺, suggesting that the rare earth element lanthanum affects the plant physiological mechanism by regulating the Ca²⁺ level in plant cell.     

Evaluation of the Adsorption of Mono- and Polytungstates onto Different Types of Clay Minerals and Pahokee Peat

Detailed knowledge about the fate and transport of tungsten in soils is critical to understanding and effectively addressing tungsten behavior in the environment. Recent studies have shown that tungsten anions may polymerize (depending upon concentration, pH, and aquatic geochemistry) in aquatic and soil systems. However, to date, of all soluble tungstate species only monotungstates have been scrutinized to a fair extent in adsorption studies. There is a lack of information evaluating adsorption mechanisms of mono- and polytungstates onto clay minerals. The objective of this work is to investigate the adsorption behavior of monotungstates (sodium tungstate, Na₂WO₄) and polytungstates (sodium metatungstate, 3Na₂WO₄·9WO₃) onto different types of clay minerals (montmorillonite, kaolinite, illite) and an organic adsorbent (Pahokee peat). Batch equilibrium experiments as a function of concentration (adsorption isotherms) and pH (adsorption envelopes) were performed to provide information about mono- and polytungstate adsorption onto clays and Pahokee peat. Adsorption equilibrium data for mono- and polytungstates onto different types of clay minerals and Pahokee peat were modeled with Freundlich and Langmuir isotherms. The adsorption affinity of clays and Pahokee peat for monotungstates follows the order: Pahokee peat>kaolinite>montmorillonite>illite; for polytungstates, the order is as follows: kaolinite>Pahokee peat>montmorillonite>illite. Results of this study suggest that the charges of the clay mineral surface, tungsten species, and solution pH are the main factors controlling tungsten adsorption. Moreover, polymeric tungsten species (i.e., metatungstate) appear to be more mobile in the environment than monomeric tungstate.     

Identification of Voltage Operated Calcium Channels by Binding Studies: Differentiation of Subclasses of Calcium Antagonist Drugs with 3H-Nimodipine Radioligand Binding

Abstract

³H-Nimodipine (³H -NIM) is a high affinity radioligand suitable to study Ca²⁺ -channels in a variety of tissues. The binding is saturable, reversible, and stereospecific in purified bovine heart and partially purified guinea-pig brain membranes. In the latter a Bmax of 600fmol/mg protein, dissociation constants (K_D) of 0.4-0.8nM and a Hill slope of 1.0 are found. At 37^C the optimal pH in 50mM TRIS-HCl buffer is 7.1-7.4. The calcium channel is a metalloprotein, and the divalent cation which is essential for the binding of ³ H -NIM can be removed by EDTA (EC₅₀ 20μM); the nimodipine binding site of the channel may then be reconstituted by divalent cations with Mn²⁺ > Ca²⁺>Mg²⁺>Sr²⁺. Ca²⁺-antagonist drugs can be divided into three main classes based on their interaction with the ³H -NIM binding site: Class I has one site law of mass action-displacement isotherms with ³H -NIM, Class II exhibits complex biphasic inhibition profiles and Class III drugs increase the affinity of 1,4 dihydropyridines for the Ca²⁺ -channel. Diltiazem is a Class III Ca²⁺ -antagonist. Our in vitro studies lead us to conclude that the Ca²⁺ -channel contains multiple regulatory sites at which drugs can act.     

Effects of lanthanum on sodium and chloride fluxes in the goldfishCarassius auratus

Summary The effect of lanthanum (La³⁺) on Na⁺ and Cl^– fluxes and on gill potentials was investigated in the goldfish,Carassius auratus. Initially La³⁺ caused large increases in both influx and efflux but after 15 min these decreased with influx returning to near normal levels while effluxes remained elevated, leading to a significant net loss of ions. Both La³⁺ and Ca²⁺ influenced gill potentials in an identical way. Possible physiological effects of La³⁺ on gill ion exchange mechanisms are discussed.     

Effect of lanthanum on 45Ca flux and secretion of protein from rat exocrine pancreas

The relationship between calcium flux and secretion of protein from rat exocrine pancreas was studied. The trivalent cation La³⁺ was used to measure ⁴⁵Ca uptake. Carbachol increased the uptake of ⁴⁵Ca into the tissue prior to onset of secretion of α-amylase. La³⁺ inhibited ⁴⁵Ca uptake in carbachol-stimulated tissue, and also inhibited secretion of protein from the pancreas. Carbachol increased the rate of efflux of ⁴⁵Ca from the pancreas independently of the presence or absence of La³⁺. In the presence of La³⁺, however, the net loss of ⁴⁵Ca from the tissue was reduced. The data suggest that La³⁺ inhibits ⁴⁵Ca influx into the pancreas and may additionally displace intracellular calcium.     

Can Fe<Superscript>3+</Superscript> and Al<Superscript>3+</Superscript> ions serve as cationic bridges to facilitate the adsorption of anionic As(V) species on humic acids? A density functional theory study

A computational chemistry investigation was undertaken to shed light on the facilitatory role played by Fe³⁺ and Al³⁺ cations in the adsorption of anionic As(V) species by humic acids through the formation of so-called cationic bridges. Geometric and energetic parameters were obtained using density functional theory at the B3LYP/6-31G(d,p) level in conjunction with the polarizable continuum model (to account for the influence of bulk water). We found that, despite their similar molecular geometries, the adsorption energies of the As(V) species AsO₄ ^3? and H₂AsO^4? differ when Fe³⁺, FeOH²⁺, Al³⁺, and AlOH²⁺ participate in the bridge. We also found that effective adsorption of As(V) species by humic acids strongly depends on whether the considered cationic bridges are tightly coordinated by humic acids at the adsorption sites, as well as on the rigidity of these humic acid adsorption sites.     

Barrier function of the cell wall during uptake of nickel ions

Cell walls were isolated from roots of six plant species to study their ion-exchange capacity for nickel ions (S _Ni) at Ni²⁺ concentration of 10⁻³ M. The S _Ni values varied depending on the plant species from 50 to 150 μmol Ni²⁺ per gram dry wt; the sorption capacity increased in a row: Poaceae < Chenopodiaceae < Fabaceae. At pH 5 the sorption capacity of cell walls for nickel ions was determined by the presence of carboxyl groups of polygalacturonic acid in the polymeric cell-wall matrix. In all cases the ion-exchange capacity of cell walls was higher at pH 8 than at pH 5, indicating that Ni²⁺ binds also to a carboxyl group different from that of polygalacturonic acid. Irrespective of plant species, the presence of EDTA in the solution diminished drastically the absorption capacity of cell walls for Ni²⁺. It is concluded that the presence of 10⁻³ M EDTA weakens the defense properties of cell walls. The sequestration of Ni²⁺ in the cell wall can be considered as an effective means of plant cell defense against elevated concentrations of nickel ions in the external medium.     

Cost-effective copper removal by electrosorption powered by microbial fuel cells

This work studied a cost-effective electrosorption that driven by microbial fuel cells (MFC-sorption) to remove Cu²⁺ from wastewater without an external energy supply. The impact factors, adsorption isotherms and kinetics of the novel process were investigated. It indicated that a low electrolyte concentration and a high solution pH could enhance the Cu²⁺ removal efficiency, while the adsorption capacity increased with the increase of numbers of MFCs in series and the initial Cu²⁺ concentration. The adsorption isotherms study indicated that the monolayer adsorption in MFC-sorption was dominant. The kinetics study suggested the increase of initial Cu²⁺ concentration could enhance the initial adsorption rate. The electrode characterizations verified the existence of Cu₂O and Cu on the electrode surface of active carbon fibers (ACFs), suggesting that MFC-sorption was not only an adsorption process, but also a redox reaction process.