Basic pH Range Research Articles

SHP-1 Variants Broaden the Understanding of pH-Dependent Activities in Protein Tyrosine Phosphatases.

The protein tyrosine phosphatase (PTP) SHP-1 plays an important role in both immune regulation and oncogenesis. This enzyme is part of a broader family of PTPs that all play important regulatory roles in vivo. Common to these enzymes is a highly conserved aspartic acid (D421 in SHP-1) that acts as an acid/base catalyst during the PTP-catalyzed reaction. This residue is located on a mobile loop, the WPD-loop, the dynamic behavior of which is intimately connected to the catalytic activity. The SHP-1 WPD-loop variants H422Q, E427A, and S418A have been kinetically characterized and compared to those of the wild-type (WT) enzyme. These variants exhibit limiting magnitudes of k cat ranging from 43 to 77% of the WT enzyme. However, their pH profiles are significantly broadened in the basic pH range. As a result, above pH 6, the E427A and S418A variants have turnover numbers notably higher than those of WT SHP-1. Molecular modeling results indicate that the shifted pH dependencies result primarily from changes in solvation and hydrogen-bonding networks that affect the pK a of the D421 residue, explaining the changes in pH-rate profiles for k cat on the basic side. In contrast, a previous study of a noncatalytic residue variant of the PTP YopH, which also exhibited changes in pH dependency, showed that the catalytic change arose from mutation-induced changes in conformational equilibria of the WPD-loop. This finding and the present study show the existence of distinct strategies for nature to tune the activity of PTPs in particular environments through controlling the pH dependency of catalysis.

Surveying the Distribution and Diversity of Predominant Mycobiota in Cultivated and Uncultivated Soils of Zaria, Northwestern Nigeria

Study’s Novelty/Excerpt This study presents a comprehensive survey of the distribution and diversity of soil fungi in cultivated and uncultivated soils of Zaria, Northwestern Nigeria, highlighting their morphological and microscopic characteristics, frequency, and relationship with physicochemical properties. It identifies and quantifies the presence of eight different fungal species, with Aspergillus niger being the most dominant, providing critical insights into the fungal biodiversity of this region. Additionally, the study correlates the richness of soil mycobiota with specific soil properties such as pH, organic matter content, and moisture levels, suggesting that these factors significantly influence fungal diversity and distribution, and recommending further research to assess their impact on soil productivity. Full Abstract Soil fungi are a crucial component of terrestrial ecosystems, playing a vital role as decomposers in nutrient cycles. The diversity of soil fungi serves as an indicator of soil health (favorable/deficient). Understanding soil biodiversity and its biological functioning will help not only in crop yields but also in a healthier society as it directly or indirectly enters the food chain. This study aimed at surveying the distribution and diversity of predominant mycobiota in cultivated and uncultivated soils of Zaria, Northwestern Nigeria. Focusing on their morphological and microscopic characteristics, percentage frequency, and relationship with physicochemical properties. After removing the surface soil, soil samples were randomly collected from two locations at 0-15 cm depths. Fungi were isolated via the dilution method on PDA. Previously established criteria were used to identify eight different fungal species: Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Fusarium spp., Mucor spp., Penicillium spp., Rhizopus spp., and Trichoderma spp. Aspergillus niger was the most dominant species, with a relative frequency of 26%, followed by Fusarium spp. and Rhizopus spp. With 18% and 17%, respectively. Aspergillus fumigatus was the least abundant (2%). The highest fungal isolation frequency (32%) was observed in L1 cultivated soil, closely followed by L2 uncultivated soil (31%), with the lowest in L2 uncultivated soil (16%). Physicochemical analysis indicated that these soils are rich in mycobiota, attributed to a basic pH range of 7.12-9.15, high organic matter content, and optimal moisture levels. Soils with significant organic matter due to litter accumulation, moist deciduous vegetation, and neutral to alkaline pH levels retain considerable moisture content, fostering a rich qualitative and quantitative mycobiota for recycling dead organic matter making nutrients available for suitable utilization. Further research is recommended to evaluate the impact of these isolated fungi on soil productivity, to determine whether their presence has a positive or negative effect.

Heavy Metal Removal from Aqueous Solutions Using a Customized Bipolar Membrane Electrodialysis Process.

Lack of safe water availability and access to clean water cause a higher risk of infectious diseases and other diseases as well. Heavy metals (HMs) are inorganic pollutants that cause severe threats to humans, animals, and the environment. Therefore, an effective HM removal technology is urgently needed. In the present study, a customized bipolar membrane electrodialysis process was used to remove HMs from aqueous solutions. The impacts of the feed ionic strength, applied electrical potential, and the type and concentration of HMs (Cd2+, Co2+, Cr3+, Cu2+, and Ni2+) on the process performance were investigated. The results showed that feed solution pH changes occurred in four stages: it first decreased linearly before stabilizing in the acidic pH range, followed by an increase and stabilization in the basic range of the pH scale. HM speciation in the basic pH range revealed the presence of anionic HM species. The presence of HMs on anion exchange membranes confirmed the contribution of these membranes for HM removal in the base channels of the process. While no clear trend was seen in the ionic strength solution, the maximum HM removal was observed when 1.5 g/L NaCl was used. The initial HM concentration showed a linear increase in HMs removal of up to 30 mg/L. A similar trend was seen with an increase in the applied electrical potential of up to 15 V. In general, the amount of HMs removed increased in the following order: Cd2+ ˃ Ni2+ ˃ Co2+ ˃ Cu2+ ˃ Cr3+. Under some operational conditions, however, the removed amount of Cu2+, Co2+, and Ni2+ was similar. The mass balance and SEM-EDX results revealed that the removed HMs were sorbed onto the membranes. In conclusion, this process efficiently separates HMs from aqueous solutions. It showed the features of diluate pH adjustment, reduction in the overall stack electrical resistance, and contribution of anion exchange membranes in multivalent cation removal. The mechanisms involved in HMs removal were diffusion and migration from the bulk solution, followed by their sorption on both cation and anion exchange membranes.

Influence of different pH milieu on the structure and function of human Aurora kinase B protein (AURK-B): Amalgamation of both spectroscopic and computational approach

Aurora kinase B (AURK-B) is a serine/threonine kinase protein that plays an essential role in chromosomal separation during the cell cycle event. AURK-B is highly expressed in various types of cancer such as human seminoma, thyroid carcinoma, non-small cell lung carcinoma (NSCLC), oral carcinoma, and gastric cancer. Hence, it is a potential therapeutic target in the treatment of various cancers. The structure of AURK-B in complex with one of its substrate inner centromeric protein (INCENP) is present, but the structural and functional characterization of native AURK-B at different pH environment is still unexplored.This study determines the effect of different pH milieu on the structure and function of AURK-B protein wherein the influence of pH on the protein conformation was probed using Circular dichroism (CD) and fluorescence spectroscopy. The structural studies were further combined with functional activity assay to observe the change in kinase activity at various pH milieu (2.0–11.0). CD and fluorescence spectroscopy experiments dictate that at high acidic conditions (pH 2.0 – 5.0), the secondary and tertiary structures of AURK-B become distorted, leading to diminished activity. The protein, however, was observed to stabilize towards pH 7.0 – 8.0 with minimal structure alteration over the basic pH range (pH 9.0 –11.0). The measured spectroscopic structural features were found to be in-line with obtained experimental kinase activity assays.Further, in-vitro experiments indicate that the enzyme is maximally active at pH 8.0. More ordered conformation and compact structure was observed at this pH (pH 8.0) as compared to other pH values through molecular dynamics simulation studies (MDS). As AURK-B localizes itself in the intracellular compartment, this study may provide a clue about the role of different pH environments in enhancing cancer growth, proliferation, and invasion.

UV-assisted photochemical transformation of a tetranuclear copper(II) complex: a DFT supported study on β-lactamase inhibitory activity towards antibiotic resistance.

Herein, we present a dark-green crystalline tetranuclear Cu(II) Schiff base complex {C1 = [Cu4L4](ClO4)4(DMF)4(H2O)} using a N,N,O donor ligand (HL), namely 2-(((2-hydroxypropyl)imino)methyl)-6-methoxyphenol. Spectro-photometrical investigation on the β-lactamase-like activity of this coordinately saturated system revealed its catalytic inefficiency towards hydrolysis of nitrocefin as a model substrate. This complex has attracted significant interest as a promising photo-catalyst owing to its narrow band gap (2.40 eV) as predicted from DFT calculations and its higher responsivity towards UV light. Therefore, C1 is effectively involved in the photocatalytic reduction of perchlorate to Cl- in the presence of a hole scavenger (H2O-MeOH) under prolonged UV irradiation and itself becomes photo-cleaved to yield a new dark-brown colored chlorobridged dinuclear crystalline complex C2 {[CuL(H2O)2Cl3]H2O}. Furthermore, C2 was deployed as a functional β-lactamase model and was found to show a remarkable catalytic proficiency towards the hydrolysis of nitrocefin in 70 : 30 (V/V) MeOH-H2O medium. This pro-catalyst C2 has been speculated to generate an aqua bridged active catalyst that plays a crucial factor in hydrolysis. This phenomenon was again experimentally established by potentiometric pH titration where C2 displays only one pKa value (7.11) in the basic pH range, indicating the deprotonation of the bridged water molecule. Based on several other kinetic studies, it may be postulated that the hydrolysis of nitrocefin is initiated by the nucleophilic attack of a bridging hydroxide, followed by very fast protonation of the intermediate to furnish the hydrolyzed product. It is noteworthy that the rate of nitrocefin hydrolysis is greatly inhibited in the presence of external chloride concentration. To the best of our knowledge, this is the first report on the photochemical behavior of such a tetranuclear copper(II) Schiff base complex. Our current interest is focused on inventing a potent β-lactamase inhibitory therapeutic as well as elucidating its mechanism through comprehensive chemical analysis.

English

Regular use of organophosphate pesticides (OPPs) such as chlorpyrolifos in agriculture results in a variety of environmental issues, including groundwater contamination, surface water pollution, enhanced floral and faunal resistance, soil acidity, reduced soil fertility, and nitrate leaching. The objective of the current study was to identify and isolate bacterial strains from native soil that could degrade chlorpyrifos and had high pesticide resistance. A total of 60 distinct microbial strains were isolated from the soil samples and subsequently evaluated for their capacity to degrade chlorpyrifos. Serratia liquefaciens, one of the strains, was discovered to be the most effective among them for degrading chlorpyrifos. It was subsequently examined for the biodegradation of chlorpyrifos under various environmental conditions and was then identified using 16S rRNA sequencing. The strain S. liquefaciens degraded more than 90% of 50 mg L-1 of chlorpyrifos. The strain performed better when urea and sucrose were used as nitrogen and carbon sources, respectively. At a temperature of 35 °C and a basic pH range, the strain functioned exceptionally well. The finding demonstrated that the bacterial strain S. liquefaciens, which was isolated from agricultural soil, is a top contender for cleaning up OPP-contaminated soil.

G-B3C2N3: A Potential Two Dimensional Metal-free Photocatalyst for Overall Water Splitting.

Based on hybrid density functional theory (DFT) calculations, we propose a new two-dimensional (2D) B-C-N material, graphitic-B3C2N3(g-B3C2N3), with the promising prospect of metal-free photocatalysis. We find it to be a near ultraviolet (UV) absorbing direct band gap (3.69 eV) semiconductor with robust dynamical and mechanical stability. Estimating the band positions with respect to water oxidation and hydrogen reduction potential levels and through a detailed analysis of reaction mechanism of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), we observe that g-B3C2N3monolayer can be efficiently used for hydrogen fuel generation over entire pH range and for spontaneous water splitting at basic pH range. Upon biaxial strain application, band positions get realigned along with the free energy change that is involved in HER and OER. Consequently, operational range of pH for OER gets broadened and the proposed material exhibits the ability to perform spontaneous and simultaneous oxidation and reduction even in neutral pH. The combination of variation in pH and applied strain can be used as a key to control the reducing or oxidizing abilities precisely for diverse photocatalytic reactions to attain environmental sustainability.

PH-equilibration of human hair: Kinetics and pH-dependence of the partition ratios for H+ − and OH− -ions based on a Freundlich isotherm

Hair is an insoluble, fibrous, α-keratinous, protein composite material, providing outer coverage, e.g., for mammals. In the context of a wider study on the effects of pH on human hair properties, we investigated the time-dependence of pH-equilibration study across the acid and the basic pH-range, using appropriate pure solutions of hydrochloric acid and sodium hydroxide. The results show that pH-equilibration follows essentially equal 1st-order kinetics across the pH-range. The characteristic process time does not change significantly and is in the range of 2.5–5 h. The analysis enables to determine the equilibrium uptakes of H+- and OH− -ions. These follow the expected U-shaped path across the pH-range. For both acidic and alkaline conditions, data are well described by two very similar sorption isotherms of the Freundlich-type. In consequence, partition ratios for both ions are highest near neutrality (pH 7: >6000) and drop off strongly towards low and high pHs (<50). Hair is thus a very strong ‘sink’ for H+ and OH−. This observation fundamentally challenges traditional views of limited ion uptake, namely, in the mid-pH-range due to hindered diffusion. It also does not support considerations on special roles of certain pHs, specific groups of amino acids, or morphological components. Our analysis thus suggests that established views of the interaction of hair and pH need to be reconsidered, The Freundlich isotherm approach appears to provide a versatile tool to refine our understanding of the interactions of hair and possibly other keratinous materials (horn, nail, feathers) with acids and bases.

Design, Development and in vitro Evaluation of Hydrogels Prepared by Free Radical Polymerization of Acrylic Acid (AAc) Containing a Model Antidiabetic Drug

Abstract: Introduction: The controlled release of medicaments in the management of diabetes is desirable to have a better therapeutic activity of the drug. Objectives: In the present study hydrogels were prepared as a controlled drug delivery system taking Rosiglitazone as a model drug. Materials and Methods: Hydrogels were created using the Free Radical Polymerization approach, with the crosslinker N, N′-Methylene bisacrylamide serving as a binding agent for the polymerization. To create a polymeric network, ammonium persulphate has been used as a polymerization inducer for AAc to poly (acrylic acid) in the existence of polyvinyl alcohol (PVP). A maximum of fifteen formulations were created with various concentrations of polymers and crosslinking agents to test the swelling, diffusion coefficients, ESR, and in vitro drug release properties of the drugs tested. The FT-IR and DSC techniques were used to determine the drug's compatibility with the polymers. The XRD studies were carried out to understand the nature of the drug contained within the hydrogel formulation. The morphologies of the surface were determined using SEM. Results and Discussion: A greater swelling was observed in the basic pH range and a marginal swelling was observed in the acidic pH range according to the swelling studies. The ESR affirmed that the pH of the hydrogels was indeed a factor in the swelling of the gels. The results of the diffusion study revealed that the diffusion coefficient has risen as a result of the reduction in cross-linker concentration and the increase in acrylic acid concentration in the solution. The in vitro release of drug data revealed that the swelling has been increased as a result of the increased concentration of acrylic acid, which resulted in the increased release of the drug. However, when the concentrations of PVP and cross-linker were increased, it was discovered that the drug release was decreased. Conclusion: AAc-PVP based hydrogel was found to be a promising controlled drug delivery system for the treatment of Rosiglitazone, according to the findings of this study. Keywords: Hydrogels, PVP Acrylic acid, Free Radical Polymerization, Antidiabetic Drug.

Functionalized copper metal-organic framework with peroxidase-mimetic activity as an adsorbent for efficient removal of noxious organic dye from aqueous solution

We show that Cu-BDC-NH 2 could be employed as a peroxidase-mimetic catalyst for Fenton-like degradation of methylene blue (MB) in water. The three-dimensional copper-based MOF was constructed solvothermally by dissolving CuCl 2 .2H 2 O and 2-amine-1, 4-benzenedicarboxylic acid (1, 4-BDC-NH 2 ) in DMF. Transmission electron microscopy, Fourier transform infrared spectroscopy, Powder X-ray diffraction, the Brunauer–Emmett–Teller technique, Thermal Gravimetric Analysis, X-ray Photoelectron Spectroscopy, UV–Vis, and fluorescence spectroscopy were used to characterize the material. The influence of pH, temperature and concentration dose of Cu-BDC-NH 2 on MB degradation was examined. According to the results, not only does Cu-BDC-NH 2 sustain a reasonably high level of activity at pH 3, but it also work efficiently in a neutral to basic pH range, showing good stability and endurance. Under ideal conditions, full removal of MB was accomplished in 60 min. The peroxidase activity provided an advantage in removing the dye in a short period of time. Selective adsorption of dyes over Cu-BDC-NH 2 were also conducted by combining two cationic dyes. The elimination of MB was above 80% after four cycles, demonstrating the high recyclability. The results show that Cu-BDC-NH 2 not only significantly adsorbs the dye but also exhibits photocatalytic activity. Because of their good activity in broader pH range, higher temperature endurance and greater recyclability for MB removal, the treatment technique may be simplified for practical use and thereby lowering treatment costs. • Cu-MOF with peroxidase-like activity is used for removal of MB dye in water. • Complete removal of MB could be achieved in 60 min. • High selectivity towards MB was achieved in 10 min even under mixed dye conditions. • Cu-MOF showed good activity in different pH, higher temperature and are recyclable.

Investigation of Factors Influencing the Photocatalytic Degradation of Pharmaceuticals, a Novel Investigation on Supported Catalysts Using UV‐A LEDs as Light Source

AbstractSupported titanium dioxide‐based photocatalysts were investigated for the degradation of pharmaceuticals under irradiation with UV−A LEDs. Focus of the presented research was placed on the degradation kinetics under different matrix influences and energy flux densities of UV−A radiation. The chemical parameters, pH, orthophosphate, nitrogen concentration and background organic concentration were investigated. The results were evaluated by time‐resolved measurement of the concentrations and by calculating and plotting the first‐order degradation rate. The results showed clear differences in the rates of degradation of each compound, with diclofenac being the most easily degraded and metoprolol the most resistant. When the influence of energy flux density was examined, a linear relationship between degradation rate and the square root of energy flux density was confirmed. The organic background matrix has a strong influence on the degradation kinetics of the compounds. Nitrogen and orthophosphate slow down the degradation much less than the organic background matrix. Investigating the pH influence, it could be shown that almost no degradation is detected in the basic pH range. The results were illustrated with the help of a radar diagram, which can show all dependencies at a glance.

The Future Is Bright for Polyoxometalates

Polyoxometalates (POMs) are clusters of units of oxoanions of transition metals, such as Mo, W, V and Nb, that can be formed upon acidification of neutral solutions. Once formed, some POMs have shown to persist in solution, even in the neutral and basic pH range. These inorganic clusters, amenable of a variety of structures, have been studied in environmental, chemical, and industrial fields, having applications in catalysis and macromolecular crystallography, as well as applications in biomedicine, such as cancer, bacterial and viral infections, among others. Herein, we connect recent POMs environmental applications in the decomposition of emergent pollutants with POMs’ biomedical activities and effects against cancer, bacteria, and viruses. With recent insights in POMs being pure, organic/inorganic hybrid materials, POM-based ionic liquid crystals and POM-ILs, and their applications in emergent pollutants degradation, including microplastics, are referred. It is perceived that the majority of the POMs studies against cancer, bacteria, and viruses were performed in the last ten years. POMs’ biological effects include apoptosis, cell cycle arrest, interference with the ions transport system, inhibition of mRNA synthesis, cell morphology changes, formation of reaction oxygen species, inhibition of virus binding to the host cell, and interaction with virus protein cages, among others. We additionally refer to POMs’ interactions with various proteins, including P-type ATPases, aquoporins, cinases, phosphatases, among others. Finally, POMs’ stability and speciation at physiological conditions are addressed.

Evaluation of aloins, pH and moisture in aloe leaf gel-based personal care products.

Some easily applicable analytical methods were explored to evaluate the quality of personal care products containing aloe leaf gel. Aloins should be absent in these products in view of their side effects. To check this, liquid chromatography (LC) was applied. The LC method used a C18monolithic column combined with gradient elution and ultraviolet (UV) detection. The mobile phase consisted of a mixture of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). The method was validated with respect to specificity, linearity, precision and accuracy. Next, it was practically applied for the analysis of commercial samples. In addition, the pH and moisture content were determined. The LC results indicated that aloins were detected in 25% of the analysed commercial samples. Further, it turned out that 42% of the test samples were found to be in the basic pH range and 33% of them contained excessive moisture. Proper quality control and adequate labelling of aloe leaf gel-based cosmetics are mandatory to avoid side effects.

Functional properties of sharpnose stingray (Dasyatis zugei) skin collagen by ultrasonication extraction as influenced by organic and inorganic acids

The aim of this study was to extract acid-soluble collagen from the skin of the sharpnose stingray using organic (acetic) and inorganic (hydrochloric) acid via an ultrasound-assisted method. The pre-treated stingray skin was extracted by 0.5M acetic acid and hydrochloric acid under ultrasonication treatment for 30 min. The collagen's properties, including viscosity, rheology, water-holding capacity (WHC), emulsifying stability index (ESI) and solubility, were determined. The yield of collagen extracted using acetic acid (11.49 ± 0.03%) was significantly higher than the yield extracted using hydrochloric acid (3.50 ± 0.01%) (p < 0.05). The viscosities of both extracted collagens were thermally stable, with a high thermal denaturation temperature (Td). The viscoelastic properties of collagen extracted using acetic acid were higher than those of collagen extracted using hydrochloric acid. The WHC and ESI for extracted collagen using acetic acid were significantly higher (47.8%, 15.01 min) than those of extracted collagen using hydrochloric acid (20.08%, 12.91 min), respectively. Both extracted collagens had higher solubility in an acidic pH range (pH 1–5) and the lowest solubility at a basic pH range (pH 9–10). Hence, these findings showed that the collagen extracted by ultrasound using acetic acid gave a higher yield and better properties than collagen extracted using hydrochloric acid.

Triapine Analogues and Their Copper(II) Complexes: Synthesis, Characterization, Solution Speciation, Redox Activity, Cytotoxicity, and mR2 RNR Inhibition.

Three new thiosemicarbazones (TSCs) HL1–HL3 as triapine analogues bearing a redox-active phenolic moiety at the terminal nitrogen atom were prepared. Reactions of HL1–HL3 with CuCl2·2H2O in anoxic methanol afforded three copper(II) complexes, namely, Cu(HL1)Cl2 (1), [Cu(L2)Cl] (2′), and Cu(HL3)Cl2 (3), in good yields. Solution speciation studies revealed that the metal-free ligands are stable as HL1–HL3 at pH 7.4, while being air-sensitive in the basic pH range. In dimethyl sulfoxide they exist as a mixture of E and Z isomers. A mechanism of the E/Z isomerization with an inversion at the nitrogen atom of the Schiff base imine bond is proposed. The monocationic complexes [Cu(L1–3)]+ are the most abundant species in aqueous solutions at pH 7.4. Electrochemical and spectroelectrochemical studies of 1, 2′, and 3 confirmed their redox activity in both the cathodic and the anodic region of potentials. The one-electron reduction was identified as metal-centered by electron paramagnetic resonance spectroelectrochemistry. An electrochemical oxidation pointed out the ligand-centered oxidation, while chemical oxidations of HL1 and HL2 as well as 1 and 2′ afforded several two-electron and four-electron oxidation products, which were isolated and comprehensively characterized. Complexes 1 and 2′ showed an antiproliferative activity in Colo205 and Colo320 cancer cell lines with half-maximal inhibitory concentration values in the low micromolar concentration range, while 3 with the most closely related ligand to triapine displayed the best selectivity for cancer cells versus normal fibroblast cells (MRC-5). HL1 and 1 in the presence of 1,4-dithiothreitol are as potent inhibitors of mR2 ribonucleotide reductase as triapine.

Siloxene: A novel 2D photocatalyst for degradation of dye molecules

Silicon based materials on 2D landscape are gaining significant interest due to their exotic properties along with well-developed processing technologies. We report use of 2D siloxene nanosheets as a potential photocatalyst for remediation of water polluted from cationic dyes. Degradation of methylene blue (MB) is used as a representative case study. Systematic studies were performed by varying reaction time, pH, material mass concentration, and dye concentration. Results suggest that adsorption mechanism is prominent over the basic pH range. Adsorption isotherms reveal that the process can be described by Langmuir model, suggesting monolayer adsorption of MB on siloxene nanosheets and pseudo second order kinetics is obeyed. Samples exhibited adsorption capacity of 8.93 mg/g of MB within equilibrium time of ∼10 min. These are also found to be effective in removal of other cationic dyes such as Azure A, Azure B and Malachite Green. Siloxene nanosheets are expected to open a new avenue for efficient remediation for treatment of textile effluents by adsorption under diffuse light.

Applicability of Mn-Mg binary oxide nanoparticles for the adsorptive removal of copper and zinc from aqueous solution

In the present study, synthesis of a novel Mn-Mg binary metal oxide was carried out using facile co-precipitation method for the possible adsorption of copper and zinc from aqueous medium. The prepared adsorbent was characterised to explore the morphology and structure using XRD and SEM. Experimental studies at batch scale were carried out examining the consequence of varying dosage of adsorbent, initial metal concentration, pH of solution and contact time on the adsorptive removal of both copper and zinc. The efficiency was found to increase with increasing dosage of adsorbent (0.1–0.5 g/L) and inversely with initial chromium concentration (10–50 ppm). Adsorption was found increasing with pH shifting from acidic to basic pH range. Adsorption isotherms plotted indicated freundlich model to be fitting better along with pseudo 2nd order kinetics.

Efficient removal of methylene blue dye from an aqueous solution using silica nanoparticle crosslinked acrylamide hybrid hydrogels

Silica nanoparticle cross-linked acrylamide polymer hydrogels showed promising adsorption behavior for organic dye removal in a neutral to basic pH range with a rapid adsorption rate, high adsorption capacity and excellent regeneration efficacy.

Conserved Amino Acid Residues that Affect Structural Stability of Candida boidinii Formate Dehydrogenase.

The NAD+-dependent formate dehydrogenase (FDH; EC 1.2.1.2) from Candida boidinii (CboFDH) has been extensively used in NAD(H)-dependent industrial biocatalysis as well as in the production of renewable fuels and chemicals from carbon dioxide. In the present work, the effect of amino acid residues Phe285, Gln287, and His311 on structural stability was investigated by site-directed mutagenesis. The wild-type and mutant enzymes (Gln287Glu, His311Gln, and Phe285Thr/His311Gln) were cloned and expressed in Escherichia coli. Circular dichroism (CD) spectroscopy was used to determine the effect of each mutation on thermostability. The results showed the decisive roles of Phe285, Gln287, and His311 on enhancing the enzyme's thermostability. The melting temperatures for the wild-type and the mutant enzymes Gln287Glu, His311Gln, and Phe285Thr/His311Gln were 64, 70, 77, and 73°C, respectively. The effects of pH and temperature on catalytic activity of the wild-type and mutant enzymes were also investigated. Interestingly, the mutant enzyme His311Gln exhibits a large shift of pH optimum at the basic pH range (1 pH unit) and substantial increase of the optimum temperature (25°C). The present work supports the multifunctional role of the conserved residues Phe285, Gln287, and His311 and further underlines their pivotal roles as targets in protein engineering studies.

Role of glycine 256 residue in improving the catalytic efficiency of mutant endoglucanase of family 5 glycoside hydrolase from Bacillus amyloliquefaciens SS35.

Wild-type, BaGH5-WT and mutant, BaGH5-UV2 (aspartate residue mutated to glycine), endoglucanases belonging to glycoside hydrolase family 5 (GH5), from wild-type, and UV2 mutant strain of Bacillus amyloliquefaciens SS35, respectively, were earlier cloned in pHTP0 cloning vector. In this study, genes encoding BaGH5-WT or BaGH5-UV2 were cloned into pET28a(+) expression-vector and expressed in Escherichia coli BL-21(DE3)pLysS cells. BaGH5-UV2 showed 10-fold (43.6 U/mg) higher specific activity against carboxymethylcellulose sodium salt (CMC-Na), higher optimal temperature by 10°C at 65°C, and 22-fold higher catalytic efficiency against CMC-Na, than BaGH5-WT. BaGH5-UV2 showed stability in wider acidic pH range (5.0-7.0) unlike BaGH5-WT in narrow basic pH range (7.0-7.5). BaGH5-UV2 displayed a mutation, Asp256Gly in L11 loop, connecting β6 -sheet with α6 -helix, near active site toward the domain surface of (α/β)8 -TIM barrel fold. Molecular dynamics simulation studies showed more stable structure, accessibility of substrate for a catalytic site, and increased flexibility of loop L11 of BaGH5-UV2 than the wild type, suggesting enhanced catalysis by BaGH5-UV2. Molecular docking analysis displayed enhanced hydrogen bond interactions of cello-oligosaccharides with BaGH5-UV2, unlike BaGH5-WT. Thus, Gly256 residue of loop L11 plays an important role in enhancing catalytic efficiency, and pH stability of GH5 endoglucanase. Therefore, these results help in protein engineering of GH5 endoglucanase for improved biochemical properties.