Defluoridation of water using adsorbent derived from the Labeo rohita (rohu) fish scales waste: Optimization,isotherms, kinetics,and thermodynamic study

Fluoride ions have more affinity towards chitosan material. Fish scales waste is chitosan material generated in abundance in fish markets with virtually no value. The present research attempts to convert this waste to useful adsorbent which can remove fluoride from water. A novel adsorbent is thus developed from the Labeo rohita (rohu) fish scales waste giving thermal treatment for removal of fluoride from water using the batch study of adsorption. Taguchi optimization approach with L₁₆ orthogonal array was adopted to optimize the process parameters for achieving the maximum removal of fluoride. Using ANOM, pH 3; initial F^? concentration 5 mg.L^?1; mixing time 90 min; adsorbent dose 8 g.L^?1 and temperature 303 ^OK were obtained as optimum values providing a maximum fluoride reduction of 93.32%. Adopting ANOVA, the percentage contribution of each process parameter in descending order of sequence is initial F^? concentration 72.44%> pH 20.61% > temperature 2.96% > adsorbent dose 2.45% > contact time 1.55%. The fluoride sorption onto fish scales adsorbent was best fitted with the pseudo-second-order kinetic model and follows the Freundlich isotherm (K_F = 0.865, 1/n = 0.407) model. Thermodynamic parameters (ΔS = ?6.32 J mol^?1.K^?1, and ΔH = ?2.02 kJ mol^?1) suggested a spontaneous, exothermic nature of adsorption and indicates a physiosorption mechanism on a heterogeneous material. SEM and FTIR analysis for surface morphology showed the presence of hydroxyl functional groups is responsible for fluoride sorption. In the regeneration studies, the F ^– exhausted adsorbent was eluted with 0.1 N NaOH and rinsed with distilled water to prepare the adsorbent for the next cycle. The study indicates the removal of fluoride from water onto fish scales adsorbent is quite feasible, cost-effective, recyclable, and better utilization of locally available waste material into useful adsorbent for defluoridation of water.     

Enhancement of CO2 adsorption on natural zeolite,modified clinoptilolite with cations,amines and ionic liquids

The modification of clinoptilolite as a natural zeolite via a simple route was carried out for CO₂ adsorption. Cation exchange with Li⁺, Mg^2+, and Ca²⁺, amine modification using monoethanolamine (MEA), triethanolamine (TEA) and hexyl amine, and ionic liquid modification using [bmim]X (X = PF₆?, NO₃?, Br?, Cl?, and bmim = 1-Butyl-3-methylimidazolium) were performed in a different amount of the modifiers. The samples were characterized by several methods (XRD, FT-IR, BET, and SEM), and adsorbed CO₂ was evaluated utilizing adsorption isotherm at a wide range of pressure. The results showed enhancement in CO₂ adsorption capacity for all the samples and 4.18, 3.58, and 4.35 times increase in CO₂ adsorption were obtained where clinoptilolite/Li⁺, clinoptilolite/2% MEA and clinoptilolite/5% [bmim]PF₆ were used as adsorbent at 4 bar pressure of CO₂, respectively.     

Preparation and characterization of a novel functionalized agricultural waste-based adsorbent for Cu2+ removal: Evaluation of adsorption performance using response surface methodology

In this study, it was aimed to the improvement of adsorption capability with a novel modification method based on increasing surface activity of flaxseed waste (FW), an agricultural waste product, and the investigation of its usability as an effective adsorbent for Cu²⁺ removal. The modification method involves functionalization of FW with iron by adding FeCl₃ to medium in presence of N, N-Dimethyl-formamide, poly (N-vinyl-pyrrolidone), and hexamethylenetetramine. The effect of parameters was investigated by conventional univariate analysis. In addition, Response Surface Methodology (RSM) based on multivariate analysis was used to improve the performance of Cu²⁺ adsorption onto iron-modified flaxseed waste (M ? FW). Cu²⁺ removal efficiency was achieved as 91.46% ± 2.34 (N = 2) at an equilibrium time of only 15 min under determined optimum conditions as Co: 75 ppm, pH: 4.7, and m: 0.23 g. RSM was successfully applied for the prediction of adsorption. Adsorption nature was as a single-layer adsorption with a maximum adsorption capacity (Q_max) of 7.64 mg/g. The adsorption mechanism, determined to be chemically controlled, an exothermic and non-spontaneous process. Furthermore, pH-dependent adsorption showed that electrostatic interactions between M ? FW and Cu²⁺ ions play an important role in adsorption mechanism. The results of characterization studies showed that a large surface area was provided with increased porosity of structure and desired changes occurred in target functional structures with modification. Moreover, modification and reusability of M ? FW were evaluated in terms of overall sustainability and waste management. The results indicated that M ? FW has potential for usability to remove heavy metals like Cu²⁺ in environmental remediation applications.     

Influence of single-walled carbon nanotubes on microbial availability of phenanthrene in sediment

Increasing production and use of single-walled carbon nanotubes (SWCNT) will inevitably lead to release of these nanoparticles to aquatic ecosystems. Similar to black carbon (BC) particles, SWCNT have a high affinity for hydrophobic organic contaminants (HOCs) and therefore the presence of SWCNT in sediment may lead to altered bioavailability of HOCs. We compared SWCNT with biochar and charcoal on their effect on the microbial degradability of 0.05 mg kg^{−1 14}C-phenanthrene (PHE) by Mycobacterium vanbaalenii PYR-1 in two sediments with different organic carbon (OC) contents. When the amendment rate of SWCNT or BC was 1 mg g⁻¹, PHE mineralization was inhibited much more significantly by SWCNT than by either biochar or charcoal. After 360 h of incubation, the mineralized fraction of PHE in the presence of SWCNT was 59.5% of the non-amended control in the sediment with low OC content, and only 42.4% in the other sediment with a higher OC content. Analysis of the freely dissolved concentration (C _free) using disposable polydimethylsiloxane (PDMS) fibers showed that SWCNT decreased C _free by 85–95%, apparently due to preferential sorption of PHE to SWCNT particles that had a much larger specific surface area and pore volume than biochar or charcoal. However, pre-interaction of SWCNT with dissolved organic matter (peptone, tannic acid, and humic acid) led to attachment of polar functional groups and reduced surface area on SWCNT, resulting in decreased PHE sorption and an alleviated effect on PHE biodegradation in the order of peptone > tannic acid > humic acid.     

Sorption of pharmaceuticals and personal care products (PPCPs) onto a sustainable cotton based adsorbent

The significant rise in contamination of wastewater, water and ground water or sediments with PPCPs is a clear evidence that nowadays applied treatment methods are inefficient in removal of these contaminants. In this study a novel cotton based adsorbent is used for efficient sorption of naproxen (NAP), caffeine (CAF) and triclosan (TCS). The adsorption of tested contaminants differed significantly: the highest amount of PPCPs sorbed was noted for TCS sorption onto CMT9 137 mg g^?1, whereas the lowest adsorbed amount, 19.73 mg g^?1, was observed for NAP sorption onto CMT13. The presence of co-solute affected both the mechanism of sorption and the amount of PPCPs sorbed: in the presence of TCS the sorption of NAP was changed from chemical to physical. Similarly, in the presence of TCS the mechanism of NAP sorption onto CMT13 changed from chemisorption to diffusion inside the pores. The presence of CAF definitely increased NAP sorption and partitioning. The presence of TCS increased CAF sorption, whereas the presence of NAP in the solution increased CAF sorption only onto CMT11. The NAP sorption in the presence of CAF was significantly enhanced and data confirmed that diffusion through the pores is the most often observed mechanism of selected PPCPs sorption onto CMTs. It is believed that the synthesized cotton-based adsorbents offer a unique opportunity for the sustainable PPCP removal from wastewater.     

High removal of crystal violet dye and tetracycline by hydrochloric acid assisted hydrothermal carbonization of sugarcane bagasse prepared at high yield

At a moderate thermal treatment process, hydrothermal carbonization (HTC) was known as an alternate and green way of preparing carbonaceous material known as hydrochar as an adsorbent. The HTC process requires the inclusion of water as a carbonization medium for the hydrolysis reaction to occur. By adding acid to the HTC water, the hydrolysis reaction was catalyzed, which lowered the reaction time and temperature while also increasing the adsorption efficiency. Overreaction, on the other hand, may occur, lowering the yield as well as the number of functional groups accessible for adsorption. Thus, in this study, Response Surface Methodology by Central Composite Design (RSM-CCD) was employed to investigate and optimize the HCL acid-assisted HTC of sugarcane bagasse (SB) process parameters of loading rate, reaction time, reaction temperature, and HCL acid concentration towards three responses: optimized hydrochar (HC_op) yield, crystal violet (CV) dye removal and tetracycline (TC) removal. The HC_op was characterized using FTIR, FESEM, BET + N₂ gas, and TGA analyses, and the results were compared to hydrochar made without the use of acid (HC_dw). In brief, HC_op has more acidic oxygenated functional groups, stronger aromaticity and hydrophobicity, greater porosity, and greater thermal stability than HC_dw. The Langmuir isotherm model reported maximum adsorption capacity (Q_max) of CV dye removal for HC_op (207.16 mg g^?1) was 1.5 times higher than the HC_dw (137.85 mg g^?1). While HC_op had a two-fold higher Q_max of TC removal (68.25 mg g^?1) than HC_dw (33.61 mg g^?1). Overall, the optimization of HCL-acid assisted HTC of SB was successful in producing hydrochar with good adsorption efficiency.     

Kinetic and isotherm studies on adsorptive removal of sulfates by cotton shell derived biochar: Recovery of sulfates from marcasite soil

This work illustrates the potential applications of the raw cotton shell (RCS) and cotton shell biochar (CSB) in the remediation of sulfate contaminants from aqueous solvents. Comprehensively, optimal batch and adsorption kinetics of sulfate by RCS and CSB were intensively analyzed and determined by varying the adsorption parameters. For RCS, the optimal series of parameters were at (pH-7, sulfate conc-150 mgL^?1, adsorbent dose- 0.5 g and time-150 min). While for CSB optimum conditions were at (pH-9.8, sulfate conc-100 mgL^?1, dosage- 0.1 g and time-90 min). The maximum adsorption efficiency for both RCS and CSB was achieved at 86.47% and 90.77%, respectively. Sulfate adsorption by RCS and CSB was examined by isotherm models and kinetic studies. The data are best suited to the Langmuir isotherm model with the highest RCS and CSB sulfate adsorption capability of 61.35 and 153.85 mg g^?1 and followed pseudo-second-order kinetics. Box-Behnken design (BBD) based response surface methodology (RSM) model-based analysis of variance test has demonstrated optimum conditions and sulfate adsorption by both RCS and CSB. The recovery studies on sulfates from marcasite soil were evaluated at different doses of RCS and CSB. This study provides insights into the usage of the developed process towards the circular economy of the sulfates.     

Performance assessment and statistical modeling of modification and adsorptive properties of a lignocellulosic waste modified using reagent assisted mechanochemical process as a low-cost and high-performance method

In this study, olive stone (OS), one of the largely-gathered agricultural wastes, was investigated as an adsorbent in modified and less efficient raw form in order to remove trace elements that have negative effects on human health and environment. Citric acid (CA) assisted mechanochemical modification method (MCM) proposed as an alternative to traditional chemical modification was presented as an innovative approach with advantages of being an easy-to-use, low-cost and eco-friendly technology. As an effective adsorbent, modified olive stone (M-OS) was used for removing Cu²⁺, Pb²⁺ and Zn²⁺ metals from aqueous solutions. Kinetic analysis was fitted with Pseudo-second-order model and equilibrium data with Langmuir model. Adsorption capacities were found as 3.49, 4.67, 2.50 mg/g with OS, and 10.10, 21.28, 18.18 mg/g with M-OS for Cu²⁺, Pb²⁺ and Zn²⁺ respectively. The removal efficiencies of all metals were above 94% for modified adsorbent in optimum conditions (C_o: 0.30 mM, pH: 5.40, and m: 0.300 g). According to thermodynamic parameters, adsorption process was spontaneous and endothermic for both adsorbents. Activation energy values indicated that nature of adsorption process was physical for OS and chemical for M-OS. In desorption and reusability studies, removal efficiencies were found as 40% and below in third cycle. In addition, financial advantages of method were revealed by cash flow and alternative selection cost analysis methods. As a result, the applied modification method was proposed as an effective, economical and green technology for modification of similar materials in today's conditions, where it is important to achieve high efficiency with lower cost.     

Human Skin is Permselective for the Small,Monovalent Cations Sodium and Potassium but not for Nickel and Chromium

The molar conductance of excised human skin (Λ_skin) immersed in electrolyte solutions comprising four cationic (Na⁺, K⁺, Ni^2 +, and Cr^3 +) and five anionic (Cl^?, NO₃^?, SO₄^2 ?, CrO₄^2 ?, and Cr₂O₇^2 ?) species was determined as a function of concentration in Franz diffusion cells. Cation transport numbers for four of these electrolytes were measured in Franz cells by the electromotive force method. Parallel experiments were conducted in solutions alone to establish the validity of the technique. Molar conductance decreased with increasing concentration, following the Kohlrausch law, over a 4–12-fold concentration range. Molar conductance and cation transport values at infinite dilution were extrapolated from these data and used to estimate ionic conductances at infinite dilution. These values were subsequently used to calculate limiting ion mobilities and diffusivities in solution and skin. Results for skin showed the expected increase in cation permselectivity for monovalent cations and a 40–110-fold reduction in effective diffusivities with respect to those in solution. However, Ni^2 + and Cr^3 + were relatively less mobile in skin than in solution. Salt diffusivities calculated from ionic mobilities in skin provided a partial explanation for the difference in allergenic potency of NiCl₂compared with NiSO₄ and Cr^3 + versus Cr^6 + salts.     

Hexamethylene diisocyanate (HDI) vapor reactivity with glutathione and subsequent transfer to human albumin

IntroductionAirway fluid glutathione (GSH) reactivity with inhaled vapors of diisocyanate, a common occupational allergen, is postulated to be a key step in exposure-induced asthma pathogenesis.MethodsA mixed (vapor/liquid) phase exposure system was used to model the in vivo reactivity of inhaled HDI vapor with GSH in the airway fluid. HDI–GSH reaction products, and their capacity to transfer HDI to human albumin, were characterized through mass spectrometry and serologic assays, using HDI-specific polyclonal rabbit serum.ResultsHDI vapor exposure of 10 mM GSH solutions resulted in primarily S-linked, bis(GSH)–HDI reaction products. In contrast, lower GSH concentrations (100 μM) resulted in mainly mono(GSH)–HDI conjugates, with varying degrees of HDI hydrolysis, dimerization and/or intra-molecular cyclization, depending upon the presence/absence of H₂PO₄^?/HPO₄^2? and Na⁺/Cl^? ions. The ion composition and GSH concentration of the fluid phase, during HDI vapor exposure, strongly influenced the transfer of HDI from GSH to albumin, as did the pH and duration of the carbamoylating reaction. When carbamoylation was performed overnight at pH 7, 25 of albumin’s lysines were identified as potential sites of conjugation with partially hydrolyzed HDI. When carbamoylation was performed at pH 9, more rapid (within 3 h) and extensive modification was observed, including additional lysine sites, intra-molecular cross-linkage with HDI, and novel HDI–GSH conjugation.ConclusionsThe data define potential mechanisms by which the levels of GSH, H₂PO₄^?/HPO₄^2?, and/or other ions (e.g. H⁺/OH^?, Na⁺, Cl^?) affect the reactivity of HDI vapor with self-molecules in solution (e.g. airway fluid), and thus, might influence the clinical response to HDI respiratory tract exposure.     

Fixed bed adsorption of Pb and Cu by iron modified bamboo,bagasse and tyre biochar

Biochar has been successfully used for remediation of inorganic and organic pollutant from aqueous and soil medium. Easy availability of raw materials, low-cost preparation, an alternative for solid waste management and efficient removal of pollutants make biochar a better option in comparison to conventional adsorbents. In the present study, effect of iron modified biochar (MBC) prepared from bamboo (Fe-BBm), bagasse (Fe-BBg) and tyre (Fe-Ty) was investigated on fixed bed adsorption of lead (Pb) and copper (Cu). Different doses of prepared biochar (BC) without modification (BBm, BBg and Ty) were also tested and compared. Mathematical parameters of breakthrough curves (BTC) were calculated to understand the adsorption of Pb and Cu by BC and MBC. The results revealed that equilibrium adsorption (qe) and removal efficiency (R%) increased with increase in dose of BC and MBC. MBC showed better breakthrough profile and adsorption than BC for Pb removal. Maximum removal of Pb (75.75%) and qe (0.15 mg/g) was done by 10% FeTy. In case of Cu removal, maximum removal (59.44%) and qe (0.12 mg/g) was found for 10% BBm. Experimental results were analysed by different models such as Thomas, Adam-Bohart and Wolborska. Experimental results of both Pb and Cu adsorption fitted well to Thomas model with R² (0.94 for Pb and 0.93 for Cu). FeTy and BBm proved better adsorbents for Pb and Cu that can be upscaled for heavy metal removal from polluted fields and large-scale environmental applications.     

Identification of phenobarbital and other barbiturates in forensic drug screening using positive electrospray ionization liquid chromatography−high resolution mass spectrometry

Comprehensive drug‐screening performed by liquid chromatography?high resolution mass spectrometry (LC?HRMS) enables identification of hundreds to thousands of drug compounds in a single analysis. Forensic drug screening is generally performed with positive electrospray ionization (ESI⁺), targeting basic drugs; however, a few toxicologically important drugs such as barbiturates, may require analysis by negative ESI. In this work, screening targets for barbiturates were determined using our LC?HRMS screening with ESI⁺. For several years, our forensic whole blood samples have been analyzed using the LC?HRMS?ESI⁺ screening in parallel with a multi‐target LC–MS/MS?ESI^? method. From 2014 to 2018, 23 samples were positive for phenobarbital (0.5?81 mg/kg). Retrospective data analysis of 4816 blood samples (15 positive) revealed several potential screening targets for phenobarbital. The targets were tentatively identified by exact mass and isotopic pattern as uncommon adducts of phenobarbital and as a decomposition product of phenobarbital N‐glucoside (C₁₇H₂₄N₂O₇). Analysis of a test set containing eight positive (0.5–65 mg/kg phenobarbital) and 31 negative samples supported the use of the observed target m/z 323.0614 at 5.14 minutes, corresponding to the [M + HCOONa+Na]⁺ adduct of phenobarbital. The [M + HCOONa+Na]⁺ adduct was confirmed as a screening target for common barbiturates, by analysis of barbiturate reference standards in ESI⁺/ESI^?. The [M + HCOONa+Na]⁺ adduct allowed retrospective analysis with 91% sensitivity (n = 23) and 100% specificity (n = 4855) for phenobarbital in our existing LC?HRMS?ESI⁺ screening. The two negative results were the two whole‐blood samples with the lowest phenobarbital concentration (<1.8 mg/kg). Thus, a specialized screening is not necessary and use of this adduct likely enables screening for other barbiturates.     

Mechanism of vasorelaxation and role of endogenous hydrogen sulfide production in mouse aorta

This study aimed to elucidate the molecular mechanism of H₂S-induced vasorelaxation. Vasorelaxation responses to the H₂S donor NaHS and the H₂S precursor l-cysteine were examined by measuring isometric tone of mouse aortic rings in a small vessel myograph. H₂S concentrations in Krebs' solution were determined with a polarographic sensor. H₂S expression was examined by Western blot, and H₂S production from CSE was assayed using a spectroscopic method. In pre-constricted mouse aorta, NaHS (1???M?C3?mM) elicited vasorelaxation of 95?±?7%, EC₅₀ 189?±?69???M. This response was unaffected by removal of the endothelium. Maximum vasorelaxation was significantly attenuated by global blockade of K⁺ channels (50?mM K⁺) and the K_ATP channel blocker glibenclamide (10???M) alone (P?<?0.01, ANOVA). Specific inhibition of K_Ca, K_IR, or K_V channels elicited a significant shift to the right in the concentration?Cresponse curve to NaHS (P?<?0.01, ANOVA) without affecting maximum relaxation. NaHS-mediated vasorelaxation was inhibited by the Cl^? channel inhibitor DIDS (1?mM, P?<?0.05, t test), and NaHS caused a significant concentration-dependent inhibition of voltage-gated Ca²⁺ channels (P?<?0.001, two-way ANOVA). The H₂S-producing enzyme cystathionine-??-lyase (CSE) was expressed in mouse aorta and had activity of 7?±?3???mol H₂S/g/min. l-cysteine (1???M?C3?mM) elicited a CSE-dependent vasorelaxation of mouse aorta with intact endothelium (20?±?7%), but not when the endothelium was removed. CSE inhibitors dl-propargylglycine (20?mM) and ??-cyanoalanine (1?mM) caused concentration-dependent contraction of mouse aorta. In mouse aorta, H₂S elicits endothelium-independent vasorelaxation involving several different ion channels and seems to converge at the vascular smooth muscle cell voltage-gated Ca²⁺ channel. The l-cysteine-CSE-H₂S pathway contributes to vasorelaxation and appears to modulate basal vessel tone.     

Toxicity of silver nanoparticles and ionic silver: Comparison of adverse effects and potential toxicity mechanisms in the freshwater clam Sphaerium corneum

Abstract

A range of studies has addressed possible environmental impacts of nanosilver, but most focused on acute effects in few species. Moreover, it remains unclear if toxic effects are particle-specific or mediated by released silver ions. We investigated chronic effects of nanosilver and soluble silver (AgNO₃) on the freshwater bivalve Sphaerium corneum. Animals were exposed to nanosilver (0–500?μg?Ag?L^?1) and AgNO₃ (0–318?μg?Ag?L^?1) over 28 days, and effects on reproduction and behavioral changes were assessed. To explore toxic mechanisms, we evaluated the effects on intracellular levels of reactive oxygen species (ROS) and the activity of antioxidant enzymes (superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase). We further explored the activity of the sodium–potassium adenosine triphosphatase (Na⁺/K⁺-ATPase). Chronic exposure to nanosilver and AgNO₃ resulted in negative effects on reproduction at concentrations of 5 and 3.18?µg?Ag?L^?1 (LOEC), respectively. ROS levels significantly increased after exposure to nanosilver at 10?µg?Ag?L^?1 and AgNO₃ at 63.5?µg?Ag?L^?1. Both forms of silver altered the activities of antioxidant enzymes. Nanosilver (500?μg?Ag?L^?1) and AgNO₃ (318?μg?Ag?L^?1) inhibited Na⁺/K⁺-ATPase activity by 82.6 and 78.9%, respectively. Nanoparticulate and soluble silver produced similar effects in S. corneum suggesting that toxicity of nanosilver is mainly mediated by dissolution of nanoparticles in the test media or after uptake by the test organisms.     

The role of Na+, K+-ATPase in the hypoxic vasoconstriction in isolated rat basilar artery

Hypoxia-induced cerebrovascular dysfunction is a key factor in the occurrence and the development of cerebral ischemia. Na⁺, K⁺-ATPase affects the regulation of intracellular Ca^2 + concentration and plays an important role in vascular smooth muscle function. However, the potential role of Na⁺, K⁺-ATPase in hypoxia-induced cerebrovascular dysfunction is unknown. In this study, we found that the KCl-induced contraction under hypoxia in rat endothelium-intact basilar arteries is similar to that of denuded arteries, suggesting that hypoxia may cause smooth muscle cell (SMC)-dependent vasoconstriction in the basilar artery. The Na⁺, K⁺–ATPase activity of the isolated basilar artery with or without endothelium significantly reduced with prolonged hypoxia. Blocking the Na⁺–Ca^2 + exchanger with Ni^2 + (10^− 3 M) or the L-type Ca^2 + channel with nimodipine (10^− 8 M) dramatically attenuated KCl-induced contraction under hypoxia. Furthermore, prolonged hypoxia significantly reduced Na⁺, K⁺-ATPase activity and increased [Ca^2 +]_i in cultured rat basilar artery SMCs. Hypoxia reduced the protein and mRNA expression of the α₂ isoform of Na⁺, K⁺-ATPase in SMCs in vitro. We used a low concentration of the Na⁺, K⁺-ATPase inhibitor ouabain, which possesses a high affinity for the α₂ isoform. The contractile response in the rat basilar artery under hypoxia was partly inhibited by ouabain pretreatment. The decreased Na⁺, K⁺-ATPase activity in isolated basilar artery and the increased [Ca^2 +]_i in SMCs induced by hypoxia were partly inhibited by pretreatment with a low concentration of ouabain. These results suggest that hypoxia may educe Na⁺, K⁺-ATPase activity in SMCs through the α₂ isoform contributing to vasoconstriction in the rat basilar artery.     

High- and low-affinity sites for sodium in δ-OR-Gi1α (Cys351-Ile351) fusion protein stably expressed in HEK293 cells; functional significance and correlation with biophysical state of plasma membrane

The effect of sodium, potassium, and lithium on δ-opioid receptor ligand binding parameters and coupling with the cognate G proteins was compared in model HEK293 cell line stably expressing PTX-insensitive δ-OR-G_i1α (Cys³⁵¹-Ile³⁵¹) fusion protein. Agonist [³H]DADLE binding was decreased in the order Na⁺???Li⁺?>?K⁺?>?(+)NMDG. When plotted as a function of increasing NaCl concentrations, the binding was best-fitted with a two-phase exponential decay considering two Na⁺-responsive sites (r ²?=?0.99). High-affinity Na⁺-sites were characterized by K_d?=?7.9 mM and represented 25 % of the basal level determined in the absence of ions. The remaining 75 % represented the low-affinity sites (K_d?=?463 mM). Inhibition of [³H]DADLE binding by lithium, potassium, and (+)-NMDG proceeded in low-affinity manner only. Surprisingly, the affinity/potency of DADLE-stimulated [³⁵S]GTPγS binding was increased in a reverse order: Na⁺?<?K⁺?<?Li⁺. This result was demonstrated in PTX-treated as well as PTX-untreated cells. Therefore, it is not restricted to G_i1α(Cys³⁵¹-Ile³⁵¹) within the δ-OR-G_i1α fusion protein, but is also valid for stimulation of endogenous G proteins of G_i/G_o family in HEK293 cells. Biophysical studies of interaction of ions with polar head-group region of lipids using Laurdan generalized polarization indicated the low-affinity type of interaction only proceeding in the order: Cs⁺?<?K⁺?<?Na⁺?<?Li⁺. The results are discussed in terms of interaction of Na⁺, K⁺ and Li⁺ with the high- and low-affinity sites located in water-accessible part of δ-OR binding pocket. We also consider the role of negatively charged Cl^?, Br^?, and I^? counter anions in inhibition of both [³H]DADLE and [³⁵S]GTPγS binding.     

Application of novel metal organic framework,MIL-53(Fe) and its magnetic hybrid: For removal of pharmaceutical pollutant,doxycycline from aqueous solutions

As a pharmaceutical pollutant, doxycycline causes contamination when enters into the environment. In this research MIL-53(Fe), and its magnetic hybrid MIL-53(Fe)/Fe₃O₄ were synthesized and employed for removal of doxycycline from aqueous solutions. The adsorbents were characterized by XRD, SEM, BET, FTIR, EDAX, VSM and TG-DTG technique. The effect of different variables such as DOC concentration, pH, contacting time, and adsorbent dose on the removal efficiency was studied and under optimized conditions the adsorption capacity of 322 mgg⁻¹ was obtained. The adsorption process was kinetically fast and the equilibration was attained within 30 min. The used adsorbent was easily separated from the solution by applying external magnetic field. The regenerated adsorbent retained most of its initial capacity after six regeneration steps. The effect of ionic strength was studied and it was indicated that removal of doxycycline from salt-containing water with moderate ionic strengths was quite feasible. Langmuir, Freundlich, Tempkin and Dubinin–Redushkevich isotherms were employed to describe the nature of adsorption process. The sorption data was well interpreted by the Longmuir model.     

Isoform specificity of cardiac glycosides binding to human Na,K-ATPase α1β1, α2β1 and α3β1

Cardiac glycosides inhibit the Na⁺,K⁺-ATPase and are used for the treatment of symptomatic heart failure and atrial fibrillation. In human heart three isoforms of Na⁺,K⁺-ATPase are expressed: α₁β₁, α₂β₁ and α₃β₁. It is unknown, if clinically used cardiac glycosides differ in isoform specific affinities, and if the isoforms have specific subcellular localization in human cardiac myocytes. Human Na⁺,K⁺-ATPase isoforms α₁β₁, α₂β₁ and α₃β₁ were expressed in yeast which has no endogenous Na⁺,K⁺-ATPase. Isoform specific affinities of digoxin, digitoxin, β-acetyldigoxin, methyldigoxin and ouabain were assessed in [³H]-ouabain binding assays in the absence or presence of K⁺ (each n = 5). The subcellular localizations of the Na⁺,K⁺-ATPase isoforms were investigated in isolated human atrial cardiomyocytes by immunohistochemistry. In the absence of K⁺, methyldigoxin (α₁ > α₃ > α₂) and ouabain (α₁ = α₃ > α₂) showed distinct isoform specific affinities, while for digoxin, digitoxin and β-acetyldigoxin no differences were found. In the presence of K⁺, also digoxin (α₂ = α₃ > α₁) and β-acetyldigoxin (α₁ > α₃) had isoform specificities. A comparison between the cardiac glycosides demonstrated highly different affinity profiles for the isoforms. Immunohistochemistry showed that all three isoforms are located in the plasma membrane and in intracellular membranes, but only α₁β₁ and α₂β₁ are located in the T-tubuli. Cardiac glycosides show distinct isoform specific affinities and different affinity profiles to Na⁺,K⁺-ATPase isoforms which have different subcellular localizations in human cardiomyocytes. Thus, in contrast to current notion, different cardiac glycoside agents may significantly differ in their pharmacological profile which could be of hitherto unknown clinical relevance.     

Nickel adsorption from aqueous solution using lemon peel biomass chemically modified with TiO2 nanoparticles

Adsorption technique has attracted considerable attention as a promising alternative for reducing heavy metal ions in water sources. This work is focused on the adsorption of nickel ions using lemon peel biomass chemically modified with titanium dioxide (TiO₂) nanoparticles through siloxane bonds. The biomass was characterized by FT-IR and compositional analyses to identify functional groups and elemental composition. From these measurements, it was observed peaks at 1741, 1328, and 1229 cm^?1, characteristics of CO, C–O, and C–H stretching bands, respectively. These organic bonds can be related to the existence of cellulose, lignin, and pectin biopolymers, which are present in the lemon peel biomass, as observed from the compositional analyses. After grafting TiO₂ nanoparticles onto lemon peel biomass surface, it was observed from FTIR the presence of vibrational bands at 1524, 1054, and 943 cm^?1, characteristics of –Ti-O-C, –Si-O-Si, and –Ti-O-Si functional groups. Additionally, the morphology and elemental composition of the lemon peel biomass modified with the titanium dioxide (TiO₂) nanoparticles were determined by SEM microscope, observing the presence of C, O, Ti, and Si atoms from the EDS mapping. Batch adsorption experiments were carried out to determine the effect of pH and biomass particle size on adsorption of Ni (II) ions from aqueous solution. From these experiments, maximum adsorption of Ni (II) ions of 78 ± 0.2% was obtained at pH 6.0, while no significant effects were observed for biomass particle size. Furthermore, the modification of biomass with TiO₂ nanoparticles increased up to 90 ± 0.1% the Ni (II) ions adsorption, suggesting the potential of the biomass modified with metal oxide nanoparticles for removal of heavy metal ions.