Enhanced sorption of Cu2+ and Ni2+ by acid-pretreated Chlorella vulgaris from single and binary metal solutions

The influence of HCl pretreatment (0.1 mM) on sorption ofCu²⁺ and Ni²⁺ by Chlorella vulgariswas tested using single and binary metal solutions. The optimal initial pH forsorption was 3.5 for Cu²⁺ and 5.5 for Ni²⁺. Second orderrate kinetics described well sorption by untreated and acid-pretreated cells.The kinetic constant q_e (metal sorption at equilibrium) for sorptionof test metals from single and binary metal solutions was increased afterpretreatment of the biomass with HCl. The Langmuir adsorption isotherm wasdeveloped for describing the various results for metal sorption. In single metalsolution, acid pretreatment enhanced q_max for Cu²⁺ andNi²⁺ sorption by approximately 70% and 65%, respectively.Cu²⁺ and Ni²⁺ mutually interfered with sorption of theother metal in the binary system. The combined presence of Cu²⁺ andNi²⁺ led to their decreased sorption by untreated biomass by 19% and88%, respectively. However, acid-pretreated biomass decreased Cu²⁺and Ni²⁺ sorption by 15 and 22%, respectively, when both the metalswere present in the solution. The results suggest a reduced mutual interferencein sorption of Cu²⁺ and Ni²⁺ from the binary metal systemdue to the acid pretreatment. Acid-pretreated cells sorbed twice the amount ofCu²⁺ and ten times that of Ni²⁺ than the untreated biomassfrom the binary metal system. Acid pretreatment more effectively enhanced thesorption of Ni²⁺ form the binary metal solution. The total metalsorption by untreated and acid-pretreated biomass depended on theCu²⁺ : Ni²⁺ ratio in the binary metal system. Acidpretreatment of C. vulgaris could be an effective andinexpensive strategy for enhancing Cu²⁺ and Ni²⁺ sorptionfrom single and binary metal solutions.     

Calcium pools,calcium entry,and cell growth

The Ca²⁺ pump and Ca²⁺ release functions of intracellular Ca²⁺ pools have been well characterized. However, the nature and identity of Ca²⁺ pools as well as the physiological implications of Ca²⁺levels within them, have remained elusive. Ca²⁺ pools appear to be contained within the endoplasmic reticulum (ER); however, ER is a heterogeneous and widely distributed organelle, with numerous other functions than Ca²⁺ regulation. Studies described here center on trying to determine more about subcellular distribution of Ca²⁺ pools, the levels of Ca²⁺ within Ca²⁺ pools, and how these intraluminal Ca²⁺ levels may be physiologically related to ER function. Experiments utilizingin situ high resolution subcellular morphological analysis of ER loaded with ratiometric fluroescent Ca²⁺ dyes, indicate a wide distribution of inositol 1,4,5-trisphosphate (InsP₃)-sensitive Ca²⁺ pools within cells, and large changes in the levels of Ca²⁺ within pools following InsP₃-mediated Ca²⁺ release. Such changes in Ca²⁺ may be of great significance to the translation, translocation, and folding of proteins in ER, in particular with respect to the function of the now numerously described luminal Ca²⁺-sensitive chaperonin proteins. Studies have also focussed on the physiological role of pool Ca²⁺ changes with respect to cell growth. Emptying of pools using Ca²⁺ pump blockers can result in cells entering a stable quiescent G₀-like growth state. After treatment with the irreversible pump blocker, thapsigargin, cells remain in this state until they are stimulated with essential fatty acids whereupon new pump protein is synthesized, functional Ca²⁺ pools return, and cells reenter the cell cycle. During the Ca²⁺ pool-depleted growth-arrested state, cells express a Ca²⁺ influx channel that is distinct from the store-operated Ca²⁺ influx channels activated after short-term depletion of Ca²⁺ pools. Overall, these studies indicate that significant changes in intraluminal ER Ca²⁺ do occur and that such changes appear linked to alteration of essential ER functions as well as to the cell cycle-state and the growth of cells.     

Modulation of Ca2+-dependent K+ transport by modifications of the NAD+/NADH ratio in intact human red cells

The effects of variations of the NAD⁺/NADH quotient on the uptake of ⁸⁶Rb by human red cells loaded by non-disruptive means with the chelator Benz2 and different amounts of ⁴⁵Ca has been examined. The NAD⁺/NADH quotient was modified by the addition of pyruvate and/or lactate or xylitol. It was found that the uptake of ⁸⁶Rb at a given intracellular Ca²⁺ concentration was faster in the reduced state (lactate or xylitol added). Metabolic changes were associated with variations of the redox state. However, glycolitic intermediates did not significantly modify the apparent affinity for Ca²⁺ of the Ca²⁺-dependent K⁺ channel in one-step inside-out vesicles prepared from the erythrocyte membrane. Taken together, these results suggest that modifications of the cytoplasmic redox potential could modulate the sensitivity to Ca²⁺ of the Ca²⁺-dependent K⁺ channel in the human red cells under physiological conditions. This conclusion is consistent with previous findings in inside-out vesicles of human erythrocytes using artificial electron donors.     

A water-soluble near-infrared fluorescent probe for specific Pd2+ detection

Palladium (Pd) is widely used in chemistry, biology, environmental science etc., and Pd²⁺ is the most plenitudinous oxidation state of the Pd that can exist under physiological conditions or in living cells, which could have adverse effects on both our health and environment. Thus, it is of great significance to monitor the changes of Pd²⁺. Hence, a novel near-infrared fluorescent probe M-PD has been developed for selective detection of Pd²⁺ based on naphthofluorescein in this work. The result demonstrated that M-PD exhibited favorable properties for sensing Pd²⁺ such as excellent water solubility, high selectivity and sensitivity. And the limit of detection was estimated as 10.8?nM, much lower than the threshold in drugs (5–10?ppm) specified by European Directorate for the Quality Control of Medicines. More importantly, detection and recovery experiments of Pd²⁺ in aspirin aqoeous solution and soil are satisfactory. In addition, M-PD has also been successfully used for near-infrared fluorescence imaging of Pd²⁺ in living cells, indicating that the probe has better feasibility and application potential in the determination of Pd²⁺.     

Sorption of Copper and Zinc to the Plasma Membrane of Wheat Root

Sorption of Cu²⁺ and Zn²⁺ to the plasma membrane (PM) of wheat root (Triticum aestivum Lcv. Scout 66) vesicles was measured at different pH values and in the presence of organic acids and other metals. The results were analyzed using a Gouy-Chapman-Stem model for competitive sorption (binding and electrostatic attraction) to a negative binding site. The binding constants for the two investigated cations as evaluated from the sorption experiments were 5 M^–1 for Zn²⁺ and 400 M^–1 for Cu²⁺. Thus, the sorption affinity of Cu²⁺ to the PM is considerably larger than that of Ca²⁺, Mg²⁺ or Zn²⁺. The greater binding affinity of Cu²⁺ was confirmed by experiments in which competition with La³⁺ for sorption sites was followed. The amount of sorbed Cu²⁺ decreased with increasing K⁺, Ca²⁺, or La³⁺ concentrations, suggesting that all these cations competed with Cu²⁺ for sorption at the PM binding sites, albeit with considerable differences among these cations in effectiveness as competitors with Cu²⁺. The sorption of Cu²⁺ and Zn²⁺ to the PM decreased in the presence of citric acid or malic acid. Citric acid (as well as pH) affected the sorption of Cu²⁺ or Zn²⁺ to PM more strongly then did malic acid.     

Removal of Cd2+, Pb2+, and Zn2+ from contaminated water using dolomite powder

Dolomite collected from Surat Thani Province in Thailand was investigated for use as a sorbent for the removal of divalent heavy metal cations from an aqueous solution. The sorbent had a surface area of 2.46 m²/g and a pH of zero point charge (pHzpc) of 9.2. Batch sorption was used to examine the effect of the pH (pH 3–7) on the sorption capacity of Cd²⁺, Pb²⁺ and Zn²⁺, alone or together as an equimolar mixture at various concentrations. Alone, each heavy metal cation was adsorbed faster at a higher pH, where the sorption of Cd²⁺ and Pb²⁺ fitted a Langmuir isotherm, but Zn²⁺ sorption best fitted a Freundlich isotherm. Under equimolar competitive sorption, the sorption capacity of each cation was decreased by 75.8% (0.29–0.07 mM/g), 82.8% (0.53–0.09 mM/g), and 95.7% (0.84–0.04 mM/g) for Cd²⁺, Pb²⁺ and Zn²⁺, respectively, compared to that with the respective single cation. Desorption of these heavy metal cations from dolomite was low, with an average desorption level of 0.06–17.4%. Furthermore, since dolomite is readily available and rather cheap, it is potentially suitable for use as an efficient sorbent to sorb Cd²⁺ and Pb²⁺, and perhaps Zn²⁺, from contaminated water.     

Comparative analysis of Ca2+-signaling in brown preadipocytes of the ground squirrel (Spermophillus undulatus) and mouse

We compared the Ca²⁺ response to noradrenalin, tapsigargin, thimerosal, and ionomycin in brown preadipocytes of the ground squirrel (Spermophillus undulatus) and mouse. The ground-squirrel brown preadipocytes did not respond to noradrenalin in concentrations within the physiological range. Stimulation of the plasma membrane Ca²⁺-channels with thimerosal showed a considerable reduction of the calcium entry in cell precursors of the both species. Intracellular calcium stores liberated in the preadipocytes of the both species by tapsigargin and ionomycin in Ca²⁺-free medium were insignificant. Ca²⁺-entry in preadipocytes was not activated by the intracellular Ca²⁺-store depletion. The Ca²⁺ response of the ground squirrel brown preadipocytes was independent of an animal’s physiological state or annual seasons. Brown preadipocytes of ground squirrels (Spermophillus undulatus) may be considered to be high ionomycin-resistant cells with reduced Ca²⁺-signaling systems.     

Biosorption of cadmium by a Cd2+-hyperresistant Bacillus cereus strain HQ-1 newly isolated from a lead and zinc mine

A Cd²⁺-hyperresistant bacterial strain HQ-1 was isolated from a lead–zinc mine. The strain was characterized and identified as Bacillus cereus based on morphology, physiological tests and 16S rRNA gene analysis. The minimal inhibitory concentration of Cd²⁺ for the bacterium was 0.012 mol/l. Isotherms for cadmium (Cd) biosorption by cells of B. cereus strain HQ-1 were investigated. The equilibrium data could be fitted by a Langmuir isotherm equation. The possible functional sites that might be influenced by the sorption were determined. The results indicate that this B. cereus strain has excellent potential for biosorption of Cd. Physiological characterization of the isolate also indicates possible application of this strain for bioremediation of sites with Cd contamination.     

Contrasting the Pb (II) and Cd (II) tolerance of Enterobacter sp. via its cellular stress responses

Successful application of microorganisms to heavy metal remediation depends on their resistance to toxic metals. This study contrasted the differences of tolerant mechanisms between Pb²⁺ and Cd²⁺ in Enterobacter sp. Microbial respiration and production of formic acid showed that Enterobacter sp. had a higher tolerant concentration of Pb (>1000 mg l⁻¹) than Cd (about 200 mg l⁻¹). Additionally, SEM confirmed that most of Pb and Cd nanoparticles (NPs) were adsorbed onto cell membrane. The Cd stress, even at low concentration (50 mg l⁻¹), significantly enlarged the sizes of cells. The cellular size raised from 0.4 × 1.0 to 0.9 × 1.6 μm on average, inducing a platelet-like shape. In contrast, Pb cations did not stimulate such enlargement even up to 1000 mg l⁻¹. Moreover, Cd NPs were adsorbed homogeneously by almost all the bacterial cells under TEM. However, only a few cells work as ‘hot spots’ on the sorption of Pb NPs. The heterogeneous sorption might result from a ‘self-sacrifice’ mechanism, i.e., some cells at a special life stage contributed mostly to Pb sorption. This mechanism, together with the lower mobility of Pb cations, caused higher microbial tolerance and removal efficiency towards Pb²⁺. This study sheds evident contrasts of bacterial resistance to the two most common heavy metals.     

Validation of TOF-SIMS and FE-SEM/EDS Techniques Combined with Sorption and Desorption Experiments to Check Competitive and Individual Pb2+ and Cd2+ Association with Components of B Soil Horizons

Sorption and desorption experiments were performed by the batch method on the B horizons of five natural soils: Umbric Cambisol, Endoleptic Luvisol, Mollic Umbrisol, Dystric Umbrisol, and Dystric Fluvisol. Individual and competitive sorption and desorption capacity and hysteresis were determined. The results showed that Pb²⁺ was sorbed and retained in a greater quantity than Cd²⁺ and that the hysteresis of the first was greater than that of the second. The most influential characteristics of the sorption and retention of Pb²⁺ were pH, ECEC, Fe and Mn oxides and clay contents. For Cd²⁺ they were mainly pH and, to a lesser extent, Mn oxides and clay content. The combined use of TOF-SIMS, FE-SEM/EDS and sorption and desorption analyses was suitable for achieving a better understanding of the interaction between soil components and the two heavy metals. They show the preferential association of Pb²⁺ with vermiculite, chlorite, Fe and Mn oxides, and of Cd²⁺ with the same components, although to a much lesser extent and intensity. This was due to the latter’s higher mobility as it competed unfavourably with the Pb²⁺ sorption sites. TOF-SIMS and FE-SEM/EDS techniques confirmed the results of the sorption experiments, and also provided valuable information on whether the soil components (individually or in association) retain Cd²⁺ and / or Pb²⁺; this could help to propose effective measures for the remediation of contaminated soils.     

Influence of Bentonite Proportion in Natural Clay on Pb2+ ions Sorption: Response Surface Methodology,Kinetics and Equilibrium Studies

The influence of natural clay's bentonite proportion on Pb²⁺ sorption capacity was investigated using response surface methodology (RSM), kinetics and equilibrium studies. Experiments were conducted at different initial pH (3–7), bentonite to clay ratio (0–100%), initial Pb²⁺ ions concentration (20–120 mg/L) and sorbent dosage (0.2–1 g). Under the RSM study, data obtained from 27 experiments undertaken were found to fitted second-order polynomial model (R² = 0.998 and R²-predicted = 0.994). Analysis of variance showed that the Pb²⁺ sorption capacity was influenced according to the order; initial concentration> mass of adsorbent > initial pH > bentonite proportion. Optimal operating conditions were obtained at initial pH 5, 0.2 g sorbent dosage, 30% bentonite to clay ratio and 100 mg/L Pb²⁺ ion concentration. Regardless of the bentonite proportion, Pb²⁺ sorption kinetics followed pseudo-second-order associated with intra-particle diffusion. The sorption isotherm for the clay which was described by Freundlich yielded higher adsorption capacity (25 mg/g) while that of the bentonite was described by Langmuir model with lower maximum sorption capacity of 15 mg/g. These results suggest that sorption of the Pb²⁺ ions was not likely to significantly impact on the removal of Pb²⁺ ions during electrokinetic remediation process of clay having different proportion of bentonite.     

Effects of methamidophos and glyphosate on copper sorption-desorption behavior in soils

A batch-equilibration technique was employed to study the impact of two organophosphorus pesticides methamidophos (MDP) and glyphosate (GPS) on copper (Cu²⁺) sorptiondesorption for phaeozem and burozem collected from Northeastern China. The addition of the two pesticides decreased Cu²⁺ sorption, increased Cu²⁺ desorption and prolonged the equilibrium time of Cu²⁺ sorption-desorption. But GPS appeared to exert a stronger influence on Cu²⁺ sorption-desorption due to its stronger complexion with Cu²⁺. When MDP was added, Cu²⁺ sorption-desorption was linearly correlated with MDP treatment concentrations. But in the presence of GPS, Cu²⁺ sorption first underwent a rapid decrease period, and then slowly tended towards a steady period. The reverse pattern could be found for Cu²⁺ desorption in the presence of GPS. Without pesticides and with the existence of MDP, Cu²⁺ sorption-desorption kinetics was well conformed to two-constant equation and Elovich equation. But that was not the case for Cu²⁺ desorption kinetics in the presence of GPS although its sorption could be also described by these two equations.     

Biosorption of long lived radionuclides using immobilized cells of Saccharomyces cerevisiae

The efficacy of immobilized Saccharomyces cerevisiae (biomatrix) for the sorption of different metal ions and its potential applications in nuclear waste treatment were investigated. The sorption of radionuclides such as ²³³U, ²⁴¹Am, ¹⁴⁴Ce, ¹³⁷Cs and ⁹⁰Sr was studied under different experimental conditions. More than 95% sorption of UO₂ ²⁺, Pu⁴⁺, Am³⁺ and Ce³⁺ could be obtained in the pH range 1 to 2 of the aqueous solutions. However the sorption of Cs⁺ and Sr²⁺ were negligible under the similar experimental conditions. The infrared spectra and scanning electron microscopic images of the control and uranium-bearing biomatrix were studied to understand the chemistry of metal uptake by this biomatrix.     

Effects of redox agents on the Ca-activated K channel

The sensitivity to Ca²⁺ of the Ca²⁺-dependent K⁺ channel can be increased by the artificial electron donor system ascorbate + phenazine-methosulphate in a variety of animal cells. In the human erythrocyte the shift from the ‘low’ to the ‘high-affinity’ state seems to depend on the reduction of a membrane component accepting 2 electrons and with an standard redox potential (pH 7.5) of about 47 mV. The relevance of this redox modulation under physiological circumstances is unknown at the moment.     

Calcium signalling in diabetes

Molecular cascades responsible for Ca²⁺ homeostasis and Ca²⁺ signalling could be assembled in highly plastic toolkits that define physiological adaptation of cells to the environment and which are intimately involved in all types of cellular pathology. Control over Ca²⁺ concentration in different cellular compartments is intimately linked to cell metabolism, because (i) ATP production requires low Ca²⁺, (ii) Ca²⁺ homeostatic systems consume ATP and (iii) Ca²⁺ signals in mitochondria stimulate ATP synthesis being an essential part of excitation–metabolic coupling. The communication between the ER and mitochondria plays an important role in this metabolic fine tuning. In the insulin resistance state and diabetes this communication has been impaired leading to different disorders, for instance, diminished insulin production by pancreatic β cells, reduced heart and skeletal muscle contractility, reduced NO production by endothelial cells, increased glucose production by liver, increased lipolysis by adipose cells, reduced immune responses, reduced cognitive functions, among others. All these processes eventually trigger degenerative events resulting in overt diabetes due to reduction of pancreatic β cell mass, and different complications of diabetes, such as retinopathy, nephropathy, neuropathy, and different cardiovascular diseases.     

Regulation of Cation-selective Channels in Liver Cells

In liver cells, cation-selective channels are permeable to Ca²⁺ and have been postulated to represent a pathway for receptor-mediated Ca²⁺ influx. This study examines the mechanisms involved in the regulation of these channels in a model liver cell line. Using patch-clamp recording techniques, it is shown that channel open probability is a saturable function of cytosolic [Ca²⁺], with half-maximal opening at 660 nm. By contrast, channel opening is not affected by membrane voltage or cytosolic pH. In intact cells, reduction of cytosolic [Cl⁻], a physiological response to Ca²⁺-mobilizing hormones and cell swelling, is also associated with an increase in channel opening. Finally, channel opening is inhibited by intracellular ATP through a mechanism that does not involve ATP hydrolysis. These findings suggest that opening of cation-selective channels is coupled to the metabolic state of the cell and provides a positive feedback mechanism for regulation of receptor-mediated Na⁺ and Ca²⁺ influx. Received: 8 October 1996     

Nuclear calcium and the regulation of the nuclear pore complex

In eukaryotic cells the nucleus and its contents are separated from the cytoplasm by the nuclear envelope. Macromolecules, as well as smaller molecules and ions, can cross the nuclear envelope through the nuclear pore complex. Molecules greater than approx. 60 kDa and containing a nuclear localization signal are actively transported across the nuclear membranes, but there has been little evidence for regulatory mechanisms for smaller molecules and ions. Recently, diffusion across the nuclear envelope has been observed to be regulated by nuclear cisternal Ca²⁺ concentrations. Following depletion of Ca²⁺ from the nuclear store by inositol 1,4,5-trisphosphate or Ca²⁺ chelators, a fluorescent 10 kDa marker molecule was no longer able to enter the nucleus. Distinct conformational states of the nuclear pore complexes depended on the Ca²⁺ filling state of the nuclear envelope, supporting the assumption that a switch in the conformation of the nuclear pore complex may control the transport of intermediate-sized molecules across the nuclear envelope. Thus nuclear Ca²⁺ stores may regulate the conformational state of the nuclear pore complex, and thereby passive diffusion of molecules between the cytosol and the nucleoplasm. The physiological significance of this finding is currently unknown.     

Biosorption with Algae: A Statistical Review

ABSTRACT

The state of the art in the field of biosorption using algae as biomass is reviewed. The available data of maximum sorption uptake (q_max) and biomass-metal affinity (b) for Cd^{2 +}, Cu^{2 +}, Ni^{2 +}, Pb^{2 +} and Zn^{2 +} were statistically analyzed using 37 different algae (20 brown algae, 9 red algae and 8 green algae). Metal biosorption research with algae has used mainly brown algae in pursuit of treatments, which improve its sorption uptake. The information available in connection with multimetallic systems is very poor. Values of q_max were close to 1 mmol/g for copper and lead and smaller for the other metals. Metal recovery performance was worse for nickel and zinc, but the number of samples for zinc was very small. All the metals except lead present a similar affinity for brown algae. The difference in the behavior of lead may be due to a different uptake mechanism. Brown algae stand out as very good biosorbents of heavy metals. The best performer for metal biosorption is lead.     

Quantitative competition of calcium with sodium or magnesium for sorption sites on plasma membrane vesicles of melon (Cucumis melo L.) root cells

The presence of Ca²⁺ ions in solution is vital for root growth. The plasma membrane is one of the first sites where competition between Ca²⁺ and other ions occurs. We studied the competition between Ca²⁺ and Na⁺ or Mg²⁺ for sorption sites on the plasma membrane of melon root cells.Sorption of ⁴⁵Ca²⁺ to right-side-out PM vesicles of melon (Cucumis melo L.) roots (prepared by aqueous two-phase partitioning) was studied at various Ca²⁺ concentrations, in the presence of increasing concentrations of Na⁺ or Mg²⁺ chlorides. Experimentally determined amounts of Ca²⁺ sorbed to the plasma membrane vesicles agreed fairly well with those calculated from a competitive sorption model. The best fit of the model to the experimental data was obtained for an average surface area of 370 Ų per charge, and binding coefficients for Na⁺, Mg²⁺ and Ca²⁺ of 0.8, 9 and 50 m ^-1, respectively.Our results suggest that nonphospholipid components in the plasma membrane contribute significantly to Ca²⁺ binding. The high affinity of Ca²⁺ binding to the plasma membrane found in this study might explain the specific role of Ca²⁺ in relieving salt stress in plant roots.This research was supported by the GIFRID German-Israel fund for research and international development.     

Potential Interactions of Calcium-Sensitive Reagents with Zinc Ion in Different Cultured Cells

BackgroundSeveral chemicals have been widely used to evaluate the involvement of free Ca²⁺ in mechanisms underlying a variety of biological responses for decades. Here, we report high reactivity to zinc of well-known Ca²⁺-sensitive reagents in diverse cultured cells.Conclusions/SignificanceTaken together, comprehensive analysis is absolutely required for the demonstration of a variety of physiological and pathological responses mediated by Ca²⁺ in diverse cells enriched of Zn²⁺.