Presence Of Buffer Research Articles

Structure and Stability of Ago2 MID-Nucleotide Complexes: All-in-One (Drop) His6-SUMO Tag Removal, Nucleotide Binding, and Crystal Growth.

The middle (MID) domain of eukaryotic Argonaute (Ago) proteins and archaeal and bacterial homologues mediates the interaction with the 5'-terminal nucleotide of miRNA and siRNA guide strands. The MID domain of human Ago2 (hAgo2) is comprised of 139 amino acids with a molecular weight of 15.56 kDa. MID adopts a Rossman-like beta1-alpha1-beta2-alpha2-beta3-alpha3-beta4-alpha4 fold with a nucleotide specificity loop between beta3 and alpha3. Multiple crystal structures of nucleotides bound to hAgo2 MID have been reported, whereby complexes were obtained by soaking ligands into crystals of MID domain alone. This protocol describes a simplified one-step approach to grow well-diffracting crystals of hAgo2 MID-nucleotide complexes by mixing purified His6-SUMO-MID fusion protein, Ulp1 protease, and excess nucleotide in the presence of buffer and precipitant. The crystal structures of MID complexes with UMP, UTP and 2'-3' linked α-L-threofuranosyl thymidine-3'-triphosphate (tTTP) are presented. This article also describes fluorescence-based assays to measure dissociation constants (Kd) of MID-nucleotide interactions for nucleoside 5'-monophosphates and nucleoside 3',5'-bisphosphates. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Crystallization of Ago2 MID-nucleotide complexes Basic Protocol 2: Measurement of dissociation constant Kd between Ago2 MID and nucleotides.

Protecting our streams by defining measurable targets for riparian management in a forestry context

Abstract Generally, governments and industry have implemented some degree of protection to reduce the impacts of forestry on aquatic ecosystems. Here, we consider the widespread application of streamside management in terms of riparian buffer retention to protect freshwaters from forestry practices across three jurisdictions with large and intensive forestry sectors (British Columbia, Finland and Sweden). This perspective was developed by working with researchers, practitioners and policymakers on mitigation measures to decrease the impacts of forestry on streams. We demonstrate that it is exceedingly rare for policies and guidelines to specify concrete objectives and measurable targets that can be assessed against riparian buffer management outcomes. Most often, policy objectives for riparian management prescribe ‘to prevent or mitigate impacts’, and this vagueness is insufficient to protect our waters. We argue that we should be clearer about the targets (outcomes) for riparian management and go beyond the simple idea that buffer presence, without further specification of its conditions, is always a successful protection strategy. One cannot measure the effectiveness of rules and guidelines without quantitative targets. Policy implications: In this paper, we suggest that locally developed and adjusted targets for riparian buffers must include quantifiable, measurable goals that specify what is supposed to be achieved and protected with respect to ecological functions, biological communities or other values. It should be relatively simple to move from current vague objectives such as ‘protect and prevent’ to a defined range of values for ecological parameters that buffers are supposed to provide. For example, these can include region‐specific shading levels and microclimate targets, large wood volumes, or riparian forest species composition. We stress that these targets must be developed through an open dialogue between agencies, practitioners, land owners and scientists. We acknowledge that there are trade‐offs between being too prescriptive and too vague. However, when excessively broad goals are the norm, we lose the capacity to effectively implement, monitor or evaluate the outcomes of protection measures.

Enhanced oxidation of micropollutants by ozone/ferrate(VI) process: Performance, mechanism, and toxicity assessment

A novel advanced oxidation technology of ozone and ferrate (ozone/Fe (VI)) was investigated and used to degrade micropollutants (e.g., sulfamethoxazole (SMX), diclofenac sodium (DCF)) in this study. The results demonstrated that the ozone/Fe(VI) process can rapidly and efficiently degrade SMX and DCF. The SMX and DCF degradation was substantially accelerated by increasing the Fe(VI) dosage (5 to 25 μM) or ozone concentration (10 to 52 μM), up to 77.0 % and 82.7 % of SMX and DCF were obtained, respectively. The removal efficiencies of SMX and DCF was higher in acidic conditions, and decreased from 98.4 % to 44.7 % and from 94.3 % to 62.9 %, respectively, at pH 5–9 in the presence of buffer. Besides, CO32−, Cl−, and HA had a little negative effect on SMX and DCF removal, and the ozone/Fe(VI) process still obtained high degradation efficiency (>64.5 %) for SMX and DCF in real water. On the basis of the finding of scavenging and probe experiments, ozone, Fe(VI), OH, and Fe(IV)/Fe(V) species were identified as the predominant oxidants for SMX and DCF degradation. Sixteen and eighteen transformation products (TPs) of SMX and DCF in ozone/Fe(VI) process were detected by UPLC-QTOF-MS. Then, the reaction pathways of SMX and DCF were proposed by Fukui function analysis and TPs identification. Using the ECOSAR software, the ecotoxicity of SMX, DCF, and their TPs were evaluated. These findings might provide useful information and a theoretical foundation for the application of ozone/Fe(VI) process in water treatment.

Solvent-Responsive Magnetic Beads for Accurate Detection of SARS-CoV-2.

Although numerous approaches were proposed for the nucleic acid (NA)-based SARS-CoV-2 detection, the nonideal NA desorption efficiency of conventional magnetic beads (MBs) limits their widespread application. In this study, we developed solvent-responsive MBs (called responsive MBs), which, in the presence of buffers, modulated the absorption and desorption capacities of NA by flipping the surface -COO-. Relative to other commercial MBs, responsive MBs exhibited similar absorption profiles and markedly enhanced desorption profiles. When applied for NA detection of complex samples, responsive MBs exhibited better performance of RNA detection than DNA, with obvious advantages in sensitivity. Specifically, the RNA and DNA desorption rates of commercial MBs were ∼85 and 82.5%, while those of responsive MBs were nearly 94 and 93.5%, respectively. Furthermore, responsive MBs exhibited remarkable extraction ability in a wide range of tissues and better performance of RNA extraction than DNA. When applied for SARS-CoV-2 detection, the responsive MBs along with the simulated digital RT-LAMP (a previously established apparatus) further improved detection efficiency, yielding a precise quantitative detection as low as 25 copies and an ultimate sensibility detection of 5 copies/mL. It was also successfully employed in numerous NA-based technologies such as polymerase chain reaction (PCR), sequencing, and so on.

Probabilistic modelling of the inherent field-level pesticide pollution risk in a small drinking water catchment using spatial Bayesian belief networks

Abstract. Pesticides are contaminants of priority concern that continue to present a significant risk to drinking water quality. While pollution mitigation in catchment systems is considered a cost-effective alternative to costly drinking water treatment, the effectiveness of pollution mitigation measures is uncertain and needs to be able to consider local biophysical, agronomic, and social aspects. We developed a probabilistic decision support tool (DST) based on spatial Bayesian belief networks (BBNs) that simulates inherent pesticide leaching risk to ground- and surface water quality to inform field-level pesticide mitigation strategies in a small (3.1 km2) drinking water catchment with limited observational data. The DST accounts for the spatial heterogeneity in soil properties, topographic connectivity, and agronomic practices; the temporal variability of climatic and hydrological processes; and uncertainties related to pesticide properties and the effectiveness of management interventions. The rate of pesticide loss via overland flow and leaching to groundwater and the resulting risk of exceeding a regulatory threshold for drinking water was simulated for five active ingredients. Risk factors included climate and hydrology (e.g. temperature, rainfall, evapotranspiration, and overland and subsurface flow), soil properties (e.g. texture, organic matter content, and hydrological properties), topography (e.g. slope and distance to surface water/depth to groundwater), land cover and agronomic practices, and pesticide properties and usage. The effectiveness of mitigation measures such as the delayed timing of pesticide application; a 10 %, 25 %, or 50 % reduction in the application rate; field buffers; and the presence/absence of soil pan on risk reduction were evaluated. Sensitivity analysis identified the month of application, the land use, the presence of buffers, the field slope, and the distance as the most important risk factors, alongside several additional influential variables. The pesticide pollution risk from surface water runoff showed clear spatial variability across the study catchment, whereas the groundwater leaching risk was uniformly low, with the exception of prosulfocarb. Combined interventions of a 50 % reduced pesticide application rate, management of the plough pan, delayed application timing, and field buffer installation notably reduced the probability of a high risk of overland runoff and groundwater leaching, with individual measures having a smaller impact. The graphical nature of BBNs facilitated interactive model development and evaluation with stakeholders to build model credibility, while the ability to integrate diverse data sources allowed a dynamic field-scale assessment of “critical source areas” of pesticide pollution in time and space in a data-scarce catchment, with explicit representation of uncertainties.

DIFFERENTIAL STABILIZING EFFECTS OF BUFFERS ON STRUCTURAL STABILITY OF BOVINE SERUM ALBUMIN AGAINST UREA DENATURATION

The conformational stability of bovine serum albumin (BSA) against urea denaturation was investigated in aqueous solutions both in the absence and presence of buffers. Various buffers differing in polar and nonpolar characters such as sodium phosphate, Tris-HCl, (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) HEPES and [3-(N-morpholino)propanesulfonic acid] MOPS buffers were used in this study. Urea-induced structural changes were analyzed using different probes, i.e., intrinsic fluorescence, ANS fluorescence and UV-difference spectral signal. Presence of different buffers in the incubation medium offered different degrees of resistance to the protein against urea-induced structural changes compared to those obtained in water (in the absence of buffers). A similar trend of buffer-induced structural resistance was noticed with three different probes. The stabilizing effect of these buffers followed the order: MOPS > HEPES > sodium phosphate > Tris-HCl > water. As found in MOPS and HEPES buffers, the highest stability of BSA can be attributed to the presence of morpholine and piperazine rings, respectively, in their structures. These groups might have produced a hydrophobic environment around the protein surface, thus stabilizing protein conformation against urea denaturation.

A Point-of-Care Quartz Biosensor Chip for Detection of PF4/Heparin Complexes

BACKGROUNDOur recent studies indicate that circulating PF4/heparin complexes activate complement and contribute to a subsequent immune response seen in heparin-induced thrombocytopenia (HIT) (Khandelwal, Blood 2016). We undertook studies to develop a sensitive assay for measuring circulating PF4/heparin. To do so, we utilize a quartz crystal microbalance (QCM) device, which is a piezoelectric acoustic resonator that detects decreases in the resonance frequency of the quartz crystal due to the increased mass caused by molecules binding to the electrode surface. We hypothesize that a novel label-free QCM biosensor functionalized with PF4/heparin capture antibodies can provide for robust quantitative antigen detection and physical characterization of antigen-antibody interactions. METHODSWe formed a mixed self-assembled monolayer by using thiol-functionalized polyethylene glycols (PEGs) with -OH and biotin terminated head-groups on gold electrodes of quartz biosensor (Nelson; Langmuir 2001). PEG-backfilling of this surface provided protein non-fouling effects (1% BSA adsorbed only 10 ng/cm2), while biotin end-groups enabled close to full surface coverage of streptavidin (180 ng/cm2). This surface became our platform to immobilize biotinylated KKO (anti-PF4/heparin IgG2Κb monoclonal antibody, developed in Arepally Lab) and TRA (isotype IgG2Κb control antibody; developed in Arepally Lab).To characterize the sensor's detection ability, we flowed recombinant PF4 (provided by M. Poncz, Children's Hospital of Philadelphia) with a range of heparin (Elkins-Sinn, NJ) concentrations. The solutions are introduced to the biosensors 10 minutes after mixing the heparin and flowed through the system until the frequency readout stabilized. We determined the amount of captured PF4/heparin complexes and the layer thickness by monitoring the sensor's resonance frequency shifts and acoustic dissipation.The surface distribution of PF4/heparin complexes on KKO-functionalized surfaces was imaged by tapping-mode atomic force microscopy (AFM). The imaging results are used to verify layer thickness calculated by acoustic modeling of the QCM signal. RESULTSIn initial experiments, KKO showed no changes in the presence of buffer or PF4 alone. However, when PF4 (10 μg/ml) was infused with increasing amounts of heparin (0.2, 1 or 10 U/ml) significant binding was detected starting at 0.2 U/ml heparin (Figure A). The acoustic modeling of the KKO-bound PF4 complexes with 0.2 U/ml heparin suggested that the macromolecular complexes were nearly 25 nm high. These results are consistent with the neutralization model for the role of PF4 in heparin-induced thrombocytopenia, in which the amount of PF4/ heparin complexes peaks at a specific molar ratio of PF4:heparin (Kowalska; Thrombosis Research 2010). Comparatively, almost no binding occurred when the quartz crystal was functionalized with TRA. This result not only demonstrates the protein non-fouling capacity of the PEG backfilling of the surface, but also shows the specificity of the surface-immobilized assay.To gauge the sensitivity of the QCM biosensor to lower concentrations of PF4 and heparin that may be found in vivo, we tested 1µg/mL PF4 with lower heparin concentrations (0.02-0.05 U/ml). As shown in Figure B, a nearly linear KKO binding response was observed in this range capable of distinguishing heparin concentrations that differed by as little as 0.01 U/ml. The highest adsorption was observed at heparin concentration of 0.02 U/ml with associated atomic force microscopy (AFM) images again showing spherical particles with 25 nm diameter on the KKO immobilized surface. CONCLUSIONSHighly specific binding to PF4 complexes demonstrates the sensitivity of the QCM platform and its ability to distinguish differences between heparin concentrations of even 0.01 U/ml. Since QCM is a mass-sensing biosensor, it has a unique sensitivity advantage while sensing high molecular weight macromolecular complexes. This, combined with possible miniaturization of the sensor and integration with lab-on-a-chip systems, creates the potential for point-of-care bed-side detection of PF4/heparin. [Display omitted] DisclosuresArepally:Biokit: Patents & Royalties.

Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water

Measurement of pH in aqueous-organic mixtures with different compositions is of high importance in science and technology, but it is, at the same time, challenging both from a conceptual and practical standpoint. A big part of the difficulty comes from the fundamental incomparability of conventional pH values between solvents (spH, solvent-specific scales). The recent introduction of the unified pH (pHabs) concept opens up the possibility of measuring pH, expressed as , in a way that is comparable between solvent, and, thereby, removing the conceptual problem. However, practical issues remain. This work presents the experience of the authors with measuring values in mixtures of methanol, ethanol, and acetonitrile, with water, but without the presence of buffers or other additives. The aim was to assigned values to solvent–water mixtures using differential potentiometry and the ‘pHabs-ladder’ method. Measurements were made of the potential difference between glass electrodes immersed in different solutions, separated by an ionic liquid salt bridge. Data were acquired for a series of solutions of varying solvent content. This work includes experiences related to: a selection of commercial electrodes, purity of starting material, and comparability between laboratories. Ranges of values for selected compositions of solvent–water mixtures are presented.

Sensitive determination of Fluoxetine and Citalopram antidepressants in urine and wastewater samples by liquid chromatography coupled with photodiode array detector

A new analyte separation and preconcentration method for the trace determination of antidepressant drugs, Fluoxetine (FLU) and Citalopram (CIT) in urine and wastewaters, was developed based on HPLC-DAD analysis after magnetic solid phase extraction (MSPE). In the proposed method, FLU and CIT were retained on the newly synthetized magnetic sorbent (Fe3O4@PPy-GO) in the presence of buffer (pH 10.0) and then were desorbed into a lower volume of acetonitrile prior to the chromatographic determinations. Before HPLC analysis, all samples were filtered through a 0.45 µm PTFE filter. Experimental parameters such as interaction time, desorption solvent and volume, and pH were studied and optimized in order to establish the detection limit, linearity, enrichment factor and other analytical figures of merit under optimum operation conditions. In the developed method, FLU and CIT were analyzed by diode array detector at the corresponding maximum wavelengths of 227 and 238 nm, respectively, by using an isocratic elution of 60% pH 3.0 buffer, 30% acetonitrile, and 10% methanol. By using the optimum conditions, limit of detections for FLU and CIT were 1.58 and 1.43 ng mL−1, respectively, while the limit of quantifications was 4.82 and 4.71 ng mL−1, respectively. Relative standard deviations (RSD%) for triplicate analyses of model solutions containing 100 ng mL−1 target molecules were found to be less than 5.0 %. Finally, the method was successfully applied to urine (both simulated and real healthy human) and wastewater samples, and quantitative results were obtained in recovery experiments.

Enzyme-immobilized flat-sheet membrane contactor for green carbon capture

• Enzyme-mediated CO 2 capture in a flat-sheet gas–liquid membrane contactor. • Biocatalytic membranes with immobilized carbonic anhydrase on amine functionalized PP. • Multiscale modeling considering enzyme attached on membrane surface and inside pores. • Mass transfer in wetted pores mitigated by enzymatic CO 2 hydration inside the pores. Membrane contactors (MC) represent an attracting system for CO 2 capture due to the enhanced mass transfer and gas–liquid interfaces, modularity, and compactness. A novel gas–liquid MC with biocatalytic flat sheet membrane was developed. The biocatalytic membrane was prepared via co-deposition of polydopamine (PDA)/ polyethyleneimine (PEI) and covalent bonding of carbonic anhydrase (CA) on polypropylene (PP) flat sheet membrane, using different deposition and enzyme immobilization conditions. The highest CA activity was achieved for 7 h deposition time, PDA/PEI ratio = 2/2, 1.0 (v/v)% glutaraldehyde, 0.8 mg/ml CA solution, 32 h immobilization time, and pH 6.0 in the immobilization process. The biocatalytic membrane showed good storage stability after 40-day. The MC performance was investigated under various conditions, including buffer type/concentration, liquid flow rate, temperature, and counter-current/co-current operating conditions. A CO 2 absorption flux of 0.29 × 10 -3 mol/m 2 s was obtained when the biocatalytic membrane was integrated into a flat sheet MC and 100 mM Tris in water was used in the absorption process. The absorption rate stability of the biocatalytic MC was also examined for several hours to verify the potential of the new flat sheet bioreactor in industrial applications. A multiscale model (with gas-filled or partially liquid-filled membrane porous structure and enzyme attached on the surface of the membrane and inside the pores) was developed to investigate the behaviour of the MC. Overall, the employment of biocatalytic membrane in flat sheet MC is a novel, green, and environmentally friendly approach allowing CO 2 capture with water (in presence of buffer) as absorbent.

Stationary Ca2+ nanodomains in the presence of buffers with two binding sites

We examine closed-form approximations for the equilibrium Ca2+ and buffer concentrations near a point Ca2+ source representing a Ca2+ channel, in the presence of a mobile buffer with two Ca2+ binding sites activated sequentially and possessing distinct binding affinities and kinetics. This allows us to model the impact on Ca2+ nanodomains of realistic endogenous Ca2+ buffers characterized by cooperative Ca2+ binding, such as calretinin. The approximations we present involve a combination or rational and exponential functions, whose parameters are constrained using the series interpolation method that we recently introduced for the case of simpler Ca2+ buffers with a single Ca2+ binding site. We conduct extensive parameter sensitivity analysis and show that the obtained closed-form approximations achieve reasonable qualitative accuracy for a wide range of buffer’s Ca2+ binding properties and other relevant model parameters. In particular, the accuracy of the derived approximants exceeds that of the rapid buffering approximation in large portions of the relevant parameter space.

Effect of cholecalciferol on unsaturated model membranes

Vitamin D plays an important role in many physiological processes, particularly calcium and phosphorous homeostasis. The biochemistry of vitamin D is also complex, encompassing a range of active molecules that may be either endogenous or dietary in origin. The role of lipids and fats in the production, processing and use of vitamin D is an interesting one, with a relative paucity of model studies into the interactions of vitamin D with lipidic systems such as micelles and vesicles. Here, we have studied the effect of vitamin D3 in simple unsaturated phospholipid systems. We used NMR and FTIR spectroscopy to investigate the effect of increasing vitamin D concentration on the structure and dynamics of the lipid chains and interfacial region. In order to link these model studies with more complex biomimetic environments, we compare results in the presence of buffer and vitamin D binding protein. We have also used DLS to determine that vitamin D3-DOPC vesicles can retain their size distribution for varying amounts of time in different conditions. We find that the acyl chain region of vitamin D3-DOPC membranes are generally disordered, and that the addition of buffer and/or protein alters the properties of the interfacial region.

Kinetics of chain reaction driven by proton-coupled electron transfer: α-hydroxyethyl radical and bromoacetate in buffered aqueous solutions.

We measured and computed the rate constants of the reaction between the α-hydroxyethyl radical (˙CH(CH3)OH) and bromoacetate (BrCH2CO2-) in the non-buffered (NB), as well as in the bicarbonate (HCO3-) and hydrogen phosphate (HPO42-) buffered aqueous solutions in the presence of ethanol. These complex multistep reactions are initiated by the proton-coupled electron transfer (PCET) which reduces BrCH2CO2- and incites its debromination. The PCET is followed by the step in which the resulting carboxymethyl radical propagates a radical chain reaction thus recovering ˙CH(CH3)OH and enhancing the debromination yields. It is found that the rate constants for the initial PCET step (k1) are raised by ca. an order of magnitude in the presence of the buffers (k1(NB) = 1.4 × 105 dm3 mol-1 s-1; k1(HCO3-) = 1.4 × 106 dm3 mol-1 s-1; k1(HPO42-) = 1.1 × 106 dm3 mol-1 s-1). To rationalize this, we used density functional theory at the M06-2X-D3/6-311+G(2d,p) level in conjunction with the polarizable continuum model (PCM) for an implicit description of the aqueous environment. To acceptably reproduce the measured rate constants, the minimal solute, consisting of ˙CH(CH3)OH, BrCH2CO2- and the buffer anion, has to be expanded by at least 2-3 explicit molecules of the water solvent. The used kinetic model consisting of a set of coupled differential equations indicates the sigmoid dependence of yields vs. k1 thereby confirming the autocatalytic trait of these reactions. The computations unravel the profound influence of the presence of buffers on these reaction systems. On the one hand, the buffer anions promote the PCET by accelerating the proton transfer; on the other hand, they slow down the propagation step by forming the strong hydrogen bonds with the carboxymethyl radical. The two opposing effects cancel out and cause the Br- yields to remain approximately comparable in the non-buffered and buffered media.

Buffer Pk a Impacts the Mechanism of Hydrogen Evolution Catalyzed By a Cobalt Porphyrin-Peptide

The effect of buffer pK a on the mechanism of electrochemical hydrogen evolution catalyzed by a cobalt porphyrin peptide (CoMP11-Ac) at constant pH is presented. The addition of buffer to CoMP11-Ac in water and KCl leads to an enhancement of the catalytic current of up to 200-fold relative to its value in the absence of a buffer. Two distinct catalytic regimes are identified as a function of the buffer pK a. In the presence of buffers with pK a ≤ 7.4, a fast catalysis regime limited by diffusion of buffer is reached. The catalytic half-wave potential (E h ) shifts anodically (from −1.42 to −1.26 V vs Ag/AgCl/KCl(1M)) as the buffer pK a decreases from 7.4 to 5.6, proposed to result from fast Co(III)-H formation following the catalysis-initiating Co(II/I) reduction. With higher-pK a buffers (pK a > 7.7), an E h = −1.42 V, proposed to reflect the Co(II/I) couple, is maintained independent of the buffer pK a, consistent with rate-limiting Co(III)-H formation under these conditions. We conclude that the buffer species pK a impacts catalytic current and potential and the rate-determining step of the reaction.

The benzene metabolite p-benzoquinone inhibits the catalytic activity of bovine liver catalase: A biophysical study

The current communication reports the inhibitory effect of para-benzoquinone (p-BQ) on the structure and function of bovine liver catalase (BLC), a vital antioxidant enzyme. Both BLC and p-BQ were dissolved in respective buffers and the biophysical interaction was studied at physiological concentrations. For the first time our data reveals an enthalpy-driven interaction between BLC and p-BQ which is due to hydrogen bonding and van der Waals interactions. The binding affinity of p-BQ with BLC is nearly 2.5 folds stronger in MOPS buffer than Phosphate buffer. Importantly, the binding affinity between BLC and p-BQ was weak in HEPES buffer as compared to other buffers being the strongest in Tris buffer. Molecular docking studies reveal that binding affinity of p-BQ with BLC differ depending upon the nature of buffers rather than on the participating amino acid residues of BLC. This is further supported by the differential changes in secondary structures of BLC. The p-BQ-induced conformational change in BLC was evident from the reduced BLC activity in presence of different buffers in the following order, Phosphate>MOPS>Tris>HEPES. The absorbance peak of BLC was gradually increased and fluorescence spectra of BLC were drastically decreased when BLC to p-BQ molar ratio was incrementally enhanced from 0 to 10,000 times in presence of all buffers. Nevertheless, the declined activity of BLC was positively correlated with the reduced fluorescence and negatively correlated with the enhanced absorbance. Electrochemical study with cyclic voltammeter also suggests a direct binding of p-BQ with BLC in presence of different buffers. Thus, p-BQ-mediated altered secondary structure in BLC results into compromised activity of BLC.

Mathematical Modeling of Calcium Oscillatory Patterns in a Neuron.

Calcium oscillations are an imperative mode of signaling phenomenon. These oscillations are due to the active interactions taking place between some of the parameters like voltage gated calcium channels (VGCC), sodium calcium exchanger (NCX), calcium binding buffers, endoplasmic reticulum (ER) and mitochondria. The present paper focuses on the problem of higher level of calcium concentration in neurons which may further result into Alzheimer's Disease (AD). For this, a three-dimensional mathematical model having a system of differential equations depicting the changes in cytosolic calcium (in presence of buffers, VGCC and NCX), ER calcium and mitochondrial calcium, is formulated. A three-dimensional neuronal structure is targeted as the domain which is further discussed and solved using finite element technique in Comsol Multiphysics 5.4. Apposite boundary conditions matching well with the in-situ conditions are assumed. The obtained results clearly show the significance of the lower amount of the buffer and higher calcium mediated activities of VGCC, NCX, ER and mitochondria on calcium profile. These changes may lead to AD. To transit from AD condition to normal, exogenous buffers are added to check their significance. The results thus show that the replenishment of buffer may balance the amount of cell calcium and hence can affect positively on Alzheimer's affected cells.

Effect of Human Plasma on Hepatic Uptake of Organic Anion-Transporting Polypeptide 1B Substrates: Studies Using Transfected Cells and Primary Human Hepatocytes.

Current challenges with the in vitro-in vivo extrapolation (IVIVE) of hepatic uptake clearance involving organic anion-transporting polypeptide (OATP) 1B1/1B3 hinder drug design strategies. Here we evaluated the effect of 100% human plasma on the uptake clearance using transfected human embryonic kidney (HEK) 293 cells and primary human hepatocytes and assessed IVIVE. Apparent unbound uptake clearance (PSinf,u) increased significantly (P < 0.05) in the presence of plasma (vs. buffer incubations) for about 50% of compounds in both OATP1B1-transfected and wild-type HEK cells. Thus, plasma showed a minimal effect on the uptake ratios. With cultured human hepatocytes, plasma significantly (P < 0.05) increased PSinf,u for 11 of 19 OATP1B substrates (median change of 2.1-fold). Cell accumulation in HEK cells and hepatocytes was also increased for tolbutamide, which is not an OATP substrate. Plasma-to-buffer ratio of PSinf,u obtained in hepatocytes showed a good correlation with unbound fraction in plasma, and the relationship was best described by a "facilitated-dissociation" model. IVIVE was evaluated for the 19 OATP1B substrates using hepatocyte data in the presence of buffer and plasma. PSinf,u from buffer incubations markedly underpredicted hepatic intrinsic clearance (calculated via well stirred and parallel tube models) with an estimated bias of 0.10-0.13. Predictions improved when using PSinf,u from plasma incubations; however, considerable systemic underprediction was still apparent (0.19-0.26 bias). Plasma data with a global scaling factor of 3.8-5.3 showed good prediction accuracy (95% predictions within 3-fold; average fold error = 1.7, bias = 1). In summary, this study offers insight into the effect of plasma on the uptake clearance and its scope in improving IVIVE. SIGNIFICANCE STATEMENT: Our study using diverse anionic compounds shows that human plasma facilitates organic anion-transporting polypeptide 1B-mediated as well as passive uptake clearance, particularly for the highly bound compounds. Leveraging data from transfected human embryonic kidney 293 cells and primary human hepatocytes, we further evaluated mechanisms involved in the observed plasma-facilitated uptake transport. Enhanced hepatic uptake rate in the presence of plasma could be of relevance, as such mechanisms likely prevail in vivo and emphasize the need to maintain physiologically relevant assay conditions to achieve improved translation of transport data.

Manipulation of spin polarization of rubidium atoms by optical pumping with both D1 and D2 beams

In this paper, we experimentally study the manipulation of the atomic spin polarization of rubidium atoms via optical pumping beams in resonance with both D1 and D2 transitions. In the presence of buffer and quenching gases, the D1 pumping beam with σ+ polarization creates atomic spin polarization along the direction of the beam, while the D2 pumping beam creates atomic spin polarization in the opposite direction. When the D1 and D2 pumping beams are simultaneously applied, the pumping processes caused by the two beams compete with each other since the D1 and D2 transitions share the same ground states. Here, we demonstrate that the resulting spin polarization of rubidium atoms is sensitive to the intensity and frequency of the D1 and D2 pumping beams. Furthermore, we show that the spin polarizations of two isotopes, 85Rb and 87Rb, can be independently manipulated with the combination of the D1 and D1 pumping beams. This provides a convenient method to create spin polarization of two isotopes of rubidium atoms in a selective manner, which may be useful in studying the spin dynamics of different isotopes in an atomic ensemble of natural abundance.

Performance of nickel-iron foam (Ni-Fe) cathode in bio-electrochemical system for hydrogen production from effluent of glucose fermentation

The high cost of Pt-based cathode, and its possibility of being poisoned by the presence of buffer in the electrolyte are two paramount issues in the BES system. The Ni-Fe has become one of the good alternatives because it has excellent catalytic properties, inexpensive, commercially available and low toxicity to microorganisms. In this study, Ni-Fe foam applied as a cathode in dual-chamber BES, while effluent of glucose fermentation as a substrate in the anode side. The characteristic of Ni-Fe surface was analyzed by using field emission scanning electron microscopy. Whereas, the catalytic property of Ni-Fe was evaluated by using linear sweep voltammetry test. The maximum hydrogen production rate and yield obtained were 500 ± 80 m3/m3/d and 470.2 ± 11.2 mL/g COD, respectively. The results show that the Ni-Fe has comparable performance to GF/Pt. Hence it could be used as an alternative cathode in BES application.

Hydrolytic Nanozymes

In 2004 we first reported catalytic nanoparticles, that are able to cleave phosphate diesters with very high efficiency (Angew. Chem. Int Ed, 2004, 43, 6165–6169) and dubbed them “nanozymes” for the similarity of their behavior with natural enzymes, both in terms of efficiency and mechanism of action. Since then the field has impressively expanded and a search on the web of science at the time of submitting this contribution returned almost 1,000 entries. This minireview highlights what has been done in the field focusing specifically on hydrolytic nanozymes, the focal point of the research in our group since its very beginning. Special emphasis is given to the advantage of bringing catalytic units in the confined space of a nanosystem in terms of inducing the cooperation between them, favoring the interaction with substrates, and altering the local environment. We will try to answer to questions like: why can a lipophilic substrate be transformed by these catalysts even in an aqueous environment? Why may the pH in the catalytic loci of the nanosystem be different from that of the bulk solution even in the presence of buffers? Why are most of these nanosystems better than monovalent ones?