Presence Of Buffer Research Articles

Long-Term Preservation of Bacteriophage Antimicrobials Using Sugar Glasses.

The antimicrobial activity of LISTEX P100, Salmonella CG4, and E. coli AG10 bacteriophages were preserved in pullulan-trehalose mixture as dried films and as coatings on food packaging. The phages encapsulated in pullulan-trehalose films were able to retain infectivity for up to 3 months at ambient storage conditions. Various buffers, disaccharides and disaccharide concentrations were investigated to optimize the long-term stability of the phages in the films. It was found that pullulan and trehalose need to be simultaneously present in the film to provide the stabilizing effect and that the presence of buffers that lead to the formation of crystals in the films must be avoided for phage activity to be maintained. Overall, this study describes a method of preserving bacteriophage activity in a dried format that has great potential for use as coatings, which can be used to create antimicrobial surfaces for food preparation and for food preservation.

Direct Spectrophotometric Determination of Lead (II) in Industrial Samples using 1, 3-Benzenediamine, N, N'-bis(2-furanylmethylene) in Presence of Surfactant

Schiff's base are one of the excellent chelating agents that used for the spectrophotometric determination of metal ions. It was observed that 1, 3-Benzenediamine, N,N'-bis(2-furanylmethylene) (BDFM) formed a brown colored complex with lead (II) at 620 nm. Lead (II) was chelated with the Schiff's base (BDFM) in acidic medium at pH = 3.5 using acetate buffer in presence of sodium laureth sulfate (SLS) as a surfactant. The effect of time, temperature and foreign ions were studied. The stoichiometric composition of the formed complex was found to be 1:2 (metal: ligand) by Job's method of continuous variation. Beer's law was obeyed in the range of 10-110 μg mL-1 with molar absorptivity 10.16×103 L mol-1cm-1. The proposed method was applied for the determination of lead in gasoline, solders, gutters and wastewater.

Preveleged Ca2+ Signaling Pathway between Membrane NCX and Mitochondria in Cardiac Myocytes

Accumulating evidence suggests that mitochondrial Ca2+ signaling plays a critical role in cardiac myocytes E-C coupling and that this may involve Ca2+ entering the mitochondria via the mitochondrial Ca2+ uniporter (MCU) and exiting on the mitochondrial Na+-Ca2+ exchanger (mNCX). Here we investigate whether there are privileged Ca2+ transport pathways between surface membrane, mitochondria and SR. To address this issue, we used genetically engineered mitochondrial Ca2+ probes based on GCamP3 and GCamP6 along with synthetic fluorescent dye, Fura-2, to image mitochondrial and cytosolic Ca2+ movements simultaneously. Mitochondrial Ca2+ probes were virally introduced in either adult or neonatal cardiomyocytes. Whole-cell patch clamping and high-resolution TIRF microscopy were used to measure membrane current, mitochondrial Ca2+ and sub-sarcolemmal cytosolic Ca2+ simultaneously. In whole cell clamped myocytes dialyzed with 2mM EGTA, Na+ withdrawal- (substituting Na+ by tetra-ethylammonium, TEA) generated an outward NCX-mediated current reflecting Ca2+ entry and caused a rapid increase of mitochondrial Ca2+, without significant rise of cytosolic Cai, because of Ca2+-buffering by 2mM EGTA. When Na+ was readmitted, causing a rapid fall (release) of mitochondrial Ca2+ it triggered a significant transient rise of cytosolic Ca2+ despite the presence of buffering by 2mM EGTA. Interestingly, 5mM caffeine puffs while triggering rapid release of Ca2+ from the SR caused little or no significant rise in the mitochondrial Ca2+ signal. Blockers of MCU or mitochondrial NCX failed to suppress this Na+ withdrawal-induced mitochondrial Ca2+ rise. Our results suggest that Ca2+ buffers may block transfer of Ca2+ from the SR via the cytosol to mitochondria without blocking the privileged Ca2+ communication between sarcolemma and mitochondria. Supported by NIH grant R0-1,HL15162

A stimuli-responsive and bioactive film based on blended polyvinyl alcohol and cashew gum polysaccharide

In this study, a stimuli-responsive, biodegradable and bioactive film was produced by blending cashew gum polysaccharide (CGP) and polyvinyl alcohol (PVA). The film presented malleability and mechanical properties enabling an easy handling. Wetting the film changed the optical property from opacity to levels of transparency higher than 70% and resulted in up to 2-fold increase in its superficial area. Different swelling indexes were obtained varying the pH of solvent, which allows classifying the CGP/PVA film as pH sensitive stimuli-responsive material. The bioactivity was achieved through covalent immobilization of papain, which remained active after storage of CGP/PVA-papain film for 24h in the presence of buffer or in a dry form. These results evidenced that CGP/PVA-papain film is a very promising material for biomedical applications.

A mathematical model of the calcium transient in urinary bladder smooth muscle cells.

An increase in cytoplasmic calcium (Ca(2+)) concentration ([Ca(2+)]i) is a prerequisite for the contraction of detrusor smooth muscle (DSM) cells . The increase in [Ca(2+)]i is accomplished by Ca(2+) entry mainly via voltage dependent L-type Ca(2+) channel and Ca(2+) release from intracellular stores. We report here a simulation of the processes that regulate intracellular Ca(2+) and their dependence on Ca(2+) concentration. Based on experimentally recorded data, mathematical equations for Ca(2+) current (generated mainly by L-type Ca(2+) channel) are developed along with representation of Ca(2+)ATPase pump currents. The plasma membrane Ca(2+)ATPase (PMCA) pump and sarco/endoplasmic reticulum Ca(2+)ATPase (SERCA) pump are responsible for lowering [Ca(2+)]i which leads to relaxation of smooth muscle. Our model simulates Ca(2+) current, action potential and the Ca(2+) transient response so as to reasonably mimic the experimental recordings. In novel findings, currents produced by PMCA and SERCA along with their amplitude and waveform pattern under voltage clamp condition have been predicted for DSM cells. The model has further been used to produce the Ca(2+) transient which results because of L-type Ca(2+) channel, Ca(2+) release from intracellular store, PMCA, SERCA and presence of buffer in the cytoplasm. To explore the model further, Ca(2+) transient decay rate in control condition is compared to the decay rate reached when PMCA and SERCA are inhibited. We conclude that this model can be used to describe the Ca(2+) transient response produced by the DSM cell in response to depolarization of cell membrane.

Design Approach of Traps Affected Source–Gate Regions in GaN HEMTs

ABSTRACTDesign of the source–gate region plays a key role in the performance of high electron mobility transistors (HEMTs) for any of its applications. In particular, the trap affected scaling of gate length and source-to-gate length directly influences the device transconductance (gm) and drain current (Ids) and hence the two main properties of the device. In this work, we investigated the effect of variations in gate length (1 to 5 µm) and source-to-gate length (1 to 3 µm). Various gate lengths and source-to-gate length designs were simulated by incorporating traps in barrier and the buffer layer. Downscaling of gate length (LG) and source-to-gate length (LSG) improved the device performance, enhanced the drain current (Ids) and device transconductance (gm). For gate length up to 2 µm, drain current showed much more reduction in the presence of buffer traps as compared to the barrier layer traps. However, this behaviour reversed for higher gate length (LG > 2 µm). For Lsg = 1 µm, the traps in buffer layers were having a more dominating effect on the reduction of Ids as compared to barrier traps. It was reversed for Lsg = 3 µm. Irrespective of Lsg and Lg variations, the presence of traps in the barrier layer showed the highest recorded gm. This strange behaviour was explained on the basis of the mobility distribution.

From Chemical Fuel Cells to Biological Fuel Cells: Challenges and Directions

Electrochemical systems as such fuel cells or batteries could play an important rule in the increasing energy demand. They are based on red-ox reactions in which the reductant gets oxidized on the anode and the oxidant gets reduced on the cathode. In low temperature fuel cells (FCs), anode and cathode are generally separated by an electrolyte that works as ionic exchange membrane. The most used low temperature abiotic FCs work utilizing hydrogen (PEMFC) or methanol (DMFC) as anode fuel and oxygen at the cathode for completing the red ox reaction.Both reactions are possible and enhanced by the utilization of inorganic catalysts mainly based on platinum. FCs are not yet commercialized and this is mainly due to the tremendous cost of noble metals as anode/cathode catalyst that corresponds to almost the 50% of the overall cost of the FC. Consequently, new lines of research were opened trying to study new non-platinum group catalysts for reducing at least one order of magnitude the cost. Moreover, improvements on the materials have been also pursed and achieved in order to avoid electrode flooding, enhance materials durability and optimize the cost-efficiency of the FC. Also water demand and sanitation is an important problem that needs to be faced and possibile solutions need to be further investigated. Recently, microbial and enzymatic red ox reactions have been utilized with different important outputs. The new field of interest called bioelectrochemistry is able to utilize different redox reactions that are achieved by bacteria metabolism or enzymatic activity. The products of those reactions in bioelectrochemical systems (BESs) are various: i) positive electrical generation, ii) removal of organics and pollutants, iii) transformation of heavy metals, iv) water desalination, v) biosensors. Moreover, if external power is applied, hydrogen or other marketable compounds can be produced. Also in this case, several problems hinder the large scale commercialization. Several anologies and differences can be found between the abiotic and biotic (BES) fuel cells but only a critical analysis of materials and processes utilized can led to real advantages for biofuel cells. In this work, we sinthesize our experience in the past years to underline our discoveries and the future directions to follow. Starting from the anode, different species of electroactive bacteria are naturally able to oxidize and consequently degrade organic compounds and release electrons on the conductive electrode mainly carbonaceous-based. Those materials have been modified in order to increase bacteria attachment, faster the start up and led to higher current generated and organics degraded. Modifications were done introducing on the surface functional groups that facilitate electroactive bacteria to attach. Further studies should be directed on better understanding the rule of surface morphology on bacteria attachment. Moreover, the selection of different bacteria consortium directly attached on the electrode for enhancing electroactivity and current generation for long time experiments need to be investigated. Different cathodes instead have been investigated. Most of the cathode utilized were based on platinum but the cost is not sustainable for large scale applications. Other options are currently investigated with the utilization of: i) oxygen reducing enzymes, ii) biocathode, iii) non-PGM catalysts, iv) high surface area activated carbons. Enzymatic reduction of oxygen has the highest electrocatalytic activity at neutral conditions but the deactivation is very fast and consequently does not seem promising. Microbial catalysis has still to be fully understood but in few cases it has been proven the positive effect of bacteria grew carbonaceous towards reduction reaction. Non-PGM and activated carbon catalysts showed high electrocatalytic activity towards oxygen reduction reaction, high durability and high resistance to get poisoned in wastewaters. Any cathode utilized suffer dramatically from precipitation of carbonates species that clogs pores and decrease performances over time. Further investigations should led to combine microbial and inorganic catalysts for further improvements. The major problem related with lab scale BESs is the optimal working conditions that often are very different compare to the natural environments boosting up significantly the output. Bacteria activity in fact is increased by high temperature, presence of buffer that has ideal pH and large availability of easily degradable organics. At the contrary, in natural environment, temperature is lower than 30°C, the pH is not always neutral and organics are much more complex to degrade. As consequence of those above mentioned causes, the achievable performances are much lower. All those improvements achieved in BESs need to be further pursued in large scale and real environment. In our opinion, the main problem remain the lack of a common design that could boost power generation and allow an efficient water treatment.

One Dimensional Finite Element Model to Study the Effect of Diffusion of Free Ca2+ in Hepatocytes

Abstract The main functional cell of the liver is hepatocyte. The frequently working of liver depends on the particular level of cytosolic Ca 2+ in hepatocyte. Cytosolic calcium is a second messenger which responsible for reproduction. Calcium controls many biological processes like movement of cell, secretion, muscular contraction, cell differentiation and buffering processes etc. The calcium diffusion in hepatocyte can be described by the system of reaction-diffusion equations. The main objective of this paper is to study the effect of diffusion of cytosolic calcium concentration in hepatocyte in presence of buffers. A one Dimensional mathematical model is developed in the form of diffusion equation. This model has studied the effect of the important parameters like immobile buffer, diffusion coefficient and influx over [Ca 2+ ] profile on hepatocyte. It is found that diffusion has significant effect in the presence of low affinity buffer compared to high affinity buffer.

Lipid-derived aldehyde degradation under thermal conditions

Nucleophilic degradation produced by reactive carbonyls plays a major role in food quality and safety. Nevertheless, these reactions are complex because reactive carbonyls are usually involved in various competitive reactions. This study describes the thermal degradation of 2-alkenals (2-pentenal and 2-octenal) and 2,4-alkadienals (2,4-heptadienal and 2,4-decadienal) in an attempt to both clarify the stability of aldehydes and determine new compounds that might also play a role in nucleophile/aldehyde reactions. The obtained results showed that alkenals and alkadienals decomposed rapidly in the presence of buffer and air to produce formaldehyde, acetaldehyde, and the aldehydes corresponding to the breakage of the carboncarbon double bonds: propanal, hexanal, 2-pentenal, 2-octenal, glyoxal, and fumaraldehyde. The activation energy of double bond breakage was relatively low (∼25kJ/mol) and the yield of alkanals (10–18%) was higher than that of 2-alkenals (∼1%). All these results indicate that these reactions should be considered in order to fully understand the range of nucleophile/aldehyde adducts produced.

Performance Evaluation of IEEE 802.11 DCF in Single Hop Ad Hoc Networks

The mathematical modeling of IEEE 802.11 CSMA/CA has received considerable attention in the past few years. However there is lack of significant work considering the presence of buffer in wireless networks. Also most of the work has not followed IEEE specifications regarding inclusion of retry limits. This paper presents a new analytical model for performance evaluation of IEEE 802.11 single hop networks. The work presented here takes into consideration the presence of first order memory buffer along with the effect of traffic arrival which obeys Poisson distribution. In addition, we have considered the short retry limit to accommodate IEEE 802.11 specifications. On one hand, lack of buffering leads to high delays and under utilization of the channel. Also the absence of short retry limit tends to overestimate the throughput. By accommodating both the shortcomings, it has been proved that our model predicts the behaviour more accurately. We have been carrying out extensive simulations to validate results of our model. We have presented the performance evaluation of both the access mechanisms present in 802.11 MAC protocol.

Variation in the structural changes of myoglobin in the presence of several protic ionic liquid

Protein stability in ionic solution depends on the delicate balance between protein–ion and ion–ion interactions. To address the ion specific effects on the protein, we have examined the stability of myoglobin (Mb) in the presence of buffer and ammonium-based ionic liquids (ILs) (50%, v/v). Here, fluorescence and circular dichroism (CD) spectroscopy experiments are used to study the influence of ILs on structure and stability of Mb. Our experimental results reveal that more viscous ILs (sulphate or phosphate ions) are stabilizers and therefore more biocompatible for Mb structure. Surprisingly, the less viscous ILs such as acetate anion based ILs are destabilizers for the native structure of Mb. Our results explicitly elucidate that anion variation has significant influence on Mb stability efficiency than cation variation. This study provides insight into anion effects on protein stability and explains that the intrasolvent interactions can be leveraged to enhance the stability.

Buffer regulation of calcium puff sequences

Puffs are localized Ca2 + signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP3). They are the result of the liberation of Ca2 + from the endoplasmic reticulum through the coordinated opening of IP3 receptor/channels clustered at a functional release site. The presence of buffers that trap Ca2 + provides a mechanism that enriches the spatio–temporal dynamics of cytosolic calcium. The expression of different types of buffers along the cell's life provides a tool with which Ca2 + signals and their responses can be modulated. In this paper we extend the stochastic model of a cluster of IP3R-Ca2 + channels introduced previously to elucidate the effect of buffers on sequences of puffs at the same release site. We obtain analytically the probability laws of the interpuff time and of the number of channels that participate of the puffs. Furthermore, we show that under typical experimental conditions the effect of buffers can be accounted for in terms of a simple inhibiting function. Hence, by exploring different inhibiting functions we are able to study the effect of a variety of buffers on the puff size and interpuff time distributions. We find the somewhat counter-intuitive result that the addition of a fast Ca2 + buffer can increase the average number of channels that participate of a puff.

Biomethane Production from Co-digestion of Banana Peel and Waste Glycerol

Banana peel and biodiesel derived glycerol are one of the most abundant agricultural waste in Southeast Asian countries. This current research demonstrated potential biomethane production from co-digestion of agricultural wastes under mesophilic fermentation. The wastes used include (1) banana peel (varying total solids in the range 2.5-10% w/v) and (2) Banana peel mixed with pure or waste glycerol. All treatments were setup in duplicate in 0.5 L batch reacotr. Gas and liquid samples were collected every 12 and 24 hr, respectively. Maximum methane production potential and yield were 181 mL and 188mL g-1 TS at 7.5% banana peel. The maximum methane production potential and yield of 7.5% banana peel mixed with 7.5 g L-1 pure glycerol (in the presence of buffer) were 467 mL and 151 mL g-1 COD, respectively, while those of 7.5% banana peel mixed with 7.5 g L-1 waste glycerol (in the presence of buffer) were 652 mL and 281 mL g-1 COD, respectively. Small amount of VFAs and ethanol was accumulated in the reactor content. The current findings indicate the potential use of glycerol waste as a co-substrate in biomethane production.

Measurements of Solute Polarizabilites Affecting Lipid Membrane Interactions

The van der Waals attraction between lipid membranes depends on the polarizability of solute molecules present in the aqueous space between neighboring membranes [1]. In particular, zwitterionic molecules (such as common pH buffers) have been shown to affect van der Waals forces more strongly than monovalent saltions [2]. Experimentally, changes in van der Waals forces are detected by x-ray scattering measurements of multilamellar lipid vesicles through the sensitivity of lamellar repeat distances to solution polarizabilities. In this respect, a direct determination of solute polarizabilities would lend support to the interpretation of x-ray data. Here we use a recently developed method [3] to quantify the polarizabilities of zwitterionic pH buffers including TAPS, TES, MES, MOPS, and HEPES. This method calculates a solution function r(c) which gives the polarizability of hydrated solutes as a function of concentration (c) by combining mass density and index of refraction measurements into a dimensionless quantity. We obtain that the zwitterionic molecules considered are significantly more polarizable than NaCl used as reference. These results are in agreement with x-ray measurements of lipid membrane interactions in the presence of buffers and monovalent salt solutions. Further, measurements of solutions 1:1 mixtures by volume have shown the polarizability is additive in agreement with theoretical models.

Finite Element Model to Study Effect of Na+/K+ Pump and Na+/Ca2+ Exchanger on Calcium Distribution in Oocytes in Presence of Buffers

Finite Element Model to Study Effect of Na+/K+ Pump and Na+/Ca2+ Exchanger on Calcium Distribution in Oocytes in Presence of Buffers

Oriented Immobilization of His-Tagged Protein on a Redox Active Thiol Derivative of DPTA-Cu(II) Layer Deposited on a Gold Electrode—The Base of Electrochemical Biosensors

This paper concerns the development of an electrochemical biosensor for the determination of Aβ16–23′ and Aβ1–40 peptides. The His-tagged V and VC1 domains of Receptor for Advanced Glycation end Products (RAGE) immobilized on a gold electrode surface were used as analytically active molecules. The immobilization of His6–RAGE domains consists of: (i) formation of a mixed layer of N-acetylcysteamine (NAC) and the thiol derivative of pentetic acid (DPTA); (ii) complexation of Cu(II) by DPTA; (iii) oriented immobilization of His6–RAGE domains via coordination bonds between Cu(II) sites from DPTA–Cu(II) complex and imidazole nitrogen atoms of a histidine tag. Each modification step was controlled by cyclic voltammetry (CV), Osteryoung square-wave voltammetry (OSWV), and atomic force microscopy (AFM). The applicability of the proposed biosensor was tested in the presence of human plasma, which had no influence on its performance. The detection limits for Aβ1–40 determination were 1.06 nM and 0.80 nM, in the presence of buffer and human plasma, respectively. These values reach the concentration level of Aβ1–40 which is relevant for determination of its soluble form in human plasma, as well as in brain. This indicates the promising future application of biosensor presented for early diagnosis of neurodegenerative diseases.

Dose and type of crystalloid fluid therapy in adult hospitalized patients.

ObjectiveIn this narrative review, an overview is given of the pros and cons of various crystalloid fluids used for infusion during initial resuscitation or maintenance phases in adult hospitalized patients. Special emphasis is given on dose, composition of fluids, presence of buffers (in balanced solutions) and electrolytes, according to recent literature. We also review the use of hypertonic solutions.MethodsWe extracted relevant clinical literature in English specifically examining patient-oriented outcomes related to fluid volume and type.ResultsA restrictive fluid therapy prevents complications seen with liberal, large-volume therapy, even though restrictive fluid loading with crystalloids may not demonstrate large hemodynamic effects in surgical or septic patients. Hypertonic solutions may serve the purpose of small volume resuscitation but carry the disadvantage of hypernatremia. Hypotonic solutions are contraindicated in (impending) cerebral edema, whereas hypertonic solutions are probably more helpful in ameliorating than in preventing this condition and improving outcome. Balanced solutions offer a better approach for plasma composition than unbalanced ones, and the evidence for benefits in patient morbidity and mortality is increasing, particularly by helping to prevent acute kidney injury.ConclusionsIsotonic and hypertonic crystalloid fluids are the fluids of choice for resuscitation from hypovolemia and shock. The evidence that balanced solutions are superior to unbalanced ones is increasing. Hypertonic saline is effective in mannitol-refractory intracranial hypertension, whereas hypotonic solutions are contraindicated in this condition.

An Experimental Study of CO2-low Salinity Water Alternating Gas Injection in Sandstone Heavy Oil Reservoirs

Several studies have shown that oil recovery significantly increased by low salinity water flooding (LSWF) in sandstones. However, mechanism of oil recovery improvement is still controversial. CO2 that develops buffer in presence of water is expected as a deterrent factor in LSWF efficiency based on mechanism of IFT reduction due to pH uprising. No bright evidence in literature supports this idea. Here, a set of core floods including a pair of CO2 WAG and a pair of water injection tests are conducted and, the efficiency of LSWF and high salinity water flooding (HSWF) were compared for each pair. HSWF was followed by LSWF in tertiary mode. Results showed that not only CO2 does not deteriorate LSWF recovery efficiency, but also improves recovery. Since CO2-low salinity WAG showed best performance among types by constant pore volume injected. Positive results in both secondary and tertiary modes with Kaolinite free samples used here showed that Kaolinite release is not the critical phenomenon in LSWF brisk performance. Also different pressure behaviour of CO2 WAG processes in comparison with reported behaviour of LSWF proves that LSWF performance may not depend on how pressure changes through flooding.

A NUMERICAL MODEL TO STUDY THE ROLE OF ADVECTION DIFFUSION OF \(Ca^{2+}\) IN MONITORING FREE \(Ca^{2+}\) CONCENTRATION IN PRESENCE OF BUFFER

Astrocytes are directly involved in synaptic processes, and may more actively contribute to the information processing in the brain than pre- viously thought. Ca 2+ signalling appears to provide the most versatile and crucial mechanisms for such a glial contribution. Intracellular calcium distri- bution is responsible to maintaining the cellular metabolic functions. Many factors that affect the cytosolic calcium concentration in Astrocytes. The main objective of this paper to study the effect of advection diffusion of cytosolic cal- cium concentration in Astrocytes in presence of buffers. A mathematical model is developed in the form of advection diffusion equation. Interdependence of all the important parameters like immobile buffer, diffusion coefficient and influx over (Ca 2+ ) profile has been studied. it is found that advection has significant effect in the presence of low affinity buffer but in the presence of high affinity buffer advection term does not show much effect on calcium concentration in

A further study of acetylacetone nitrosation

The nitrosation of acetylacetone (AcAc) has been revised in an aqueous acid medium of perchloric acid and buffers of mono-, di-, or tri-chloroacetic acid. The results show that in the presence of buffers, under conditions of [nit] ≪ [AcAc] (nit = sodium nitrite) the reaction cannot be studied by UV-Vis spectroscopy, contrary to the recently published paper by García-Rio et al. (J. Org. Chem., 2008, 73, 8198). The present study also corroborates the previously published mechanism of AcAc nitrosation, where no base-catalysis was observed. Contrarily, the low effect of buffers was attributed to the formation of nitrosyl chloro-, dichloro- or trichloro-acetate salts that are new nitrosating agents.