Na-acetate Buffer Research Articles

Synthesis and characterization of ZSM-5 zeolite with micro- and hierarchical pore structures from Bayatnatural zeolite

Synthesis of ZSM-5 (Zeolite Socony Mobil-5) has been carried out using Bayat natural zeolite as silica and alumina source. Pretreatment on Bayat natural zeolite was performed through the process of activation, purification, dealumination, and fragmentation. The purpose of activation process is to remove the polar impurities, free oxide in the surface that cover up the pores and release the water that trapped in the pores of the crystals. The purification was conducted using Na-acetate buffer solution with ratio 1:3 (w/v). The dealumination process with 2M HCl was carried out to increase the Si/Al ratio. Fragmentation process then was carried out by using NaOH as much as 50% of NaOH was mixed with Bayat natural zeolite. Synthesis of ZSM-5 was performed using single templates method by adding TPAOH (Tetrapropylammonium hydroxide) as micropore structure directing agent. Furthermore, synthesis of hierarchical ZSM-5 using double templates method was also carried out in which PDDAM (Poly(acrylamide-co-diallyldimethylammonium chloride)) as mesoporous directing agent. The results showed xRD pattern of Microporous ZSM-5 and Hierarchical ZSM-5 had specific peaks at position 2 theta position of 7-10° and 22-25° which are the characteristics of ZSM-5 zeolite. The Si/Al molar ratio of microporous ZSM-5 and hierarchical ZSM-5 are 32.34 and 43.53.

Methods and extractants to evaluate silicon availability for sugarcane

The correct evaluation of silicon (Si) availability in different soil types is critical in defining the amount of Si to be supplied to crops. This study was carried out to evaluate two methods and five chemical Si extractants in clayey, sandy-loam, and sandy soils cultivated with sugarcane (Saccharum spp. hybrids). Soluble Si was extracted using two extraction methods (conventional and microwave oven) and five Si extractants (CaCl2, deionized water, KCl, Na-acetate buffer (pH 4.0), and acetic acid). No single method and/or extractant adequately estimated the Si availability in the soils. Conventional extraction with KCl was no more effective than other methods in evaluating Si availability; however, it had less variation in estimating soluble Si between soils with different textural classes. In the clayey and sandy soils, the Na-acetate buffer (pH 4.0) and acetic acid were effective in evaluating the Si availability in the soil regardless of the extraction methods. The extraction with acetic acid using the microwave oven, however, overestimated the Si availability. In the sandy-loam soil, extraction with deionized water using the microwave oven method was more effective in estimating the Si availability in the soil than the other extraction methods.

Purificación y caracterización preliminar de proteasas del látex de Vasconcellea candicans (A. Gray) A. DC (Mito)

Preliminary studies indicate that, the Mito fresh latex, has a specific activity of papain from 1.84 times greater than that found in the latex of papaya, so the objective of this study was to purify and characterize Mito fresh latex proteases that have activity of papain. The crude extract protease was obtained from the Mito latex which was re-suspended (1:1) in 10 mM Na acetate buffer at pH 5.0; immediately proteins were precipitated at pH 9.0 and then with 45% ammonium sulfate. Subsequently, the proteins were purified on a Sephadex G-100 column and were three fractions: A, B and C. Using as a substrate casein, the enzymatic specific activity (ESA) was measured and was found to be the fraction A was 87.74 nkat.mg-1protein, for fraction B was 14.93 nkat.mg-1protein and for fraction C it was 16.13 nkat.mg-1protein. ESA of fraction A against papain of fresh latex of C. papaya was 13.3 times greater. Electrophoretic analysis (12% denaturant gel) shows for A fraction, two protein bands having one of them a relation similar to the papain standard. In addition, there was observed that the A fraction (papain of Mito) against different concentrations of casein, used as a substrate, displays a michaeliane sigmoid curve; different volumes of enzyme shows a linear behavior; it has an optimum pH of 7.5 and is active up to 60 °C.

Suppression of Pyrite Oxidation by Formation of Iron Hydroxide and Fe(III)-silicate Complex under Highly Oxidizing Condition

Acid drainage generated by pyrite oxidation has caused the acidification of soil and surface water, the heavy metal contamination and the corrosion of structures in abandoned mine and construction sites. The applicability of Na-acetate (Na-OAc) buffer and/or Na-silicate solution was tested for suppressing pyrite oxidation by reacting pyrite containing rock and treating solution and by analyzing solution chemistry after the reaction. A finely ground Mesozoic andesite containing 10.99% of pyrite and four types of reacting solutions were used in the applicability test: 1) <TEX>$H_2O_2$</TEX>, 2) <TEX>$H_2O_2$</TEX> and Na-silicate, 3) <TEX>$H_2O_2$</TEX> and 0.01M Na-OAc buffer at pH 6.0, and 4) <TEX>$H_2O_2$</TEX>, Na-silicate and 0.01M Na-OAc buffer at pH 6.0. The pH in the solution after the reaction with the andesite sample and the solutions was decreased with increasing the initial <TEX>$H_2O_2$</TEX> concentration but the concentrations of Fe and <TEX>$SO_4^{2-}$</TEX> were increased 10 - 20 times. However, the pH of the solution after the reaction increased and the concentrations of Fe and <TEX>$SO_4^{2-}$</TEX> decreased in the presence of Na-acetate buffer and with increasing Na-silicate concentration at the same <TEX>$H_2O_2$</TEX> concentration. The solution chemistry indicates that Na-OAc buffer and Na-silicate suppress the oxidation of pyrite due to the formation of Fe-hydroxide and Fe-silicate complex and their coating on the pyrite surface. The effect of Na-OAc buffer and Na-silicate on reduction of pyrite oxidation was also confirmed with the surface examination of pyrite using scanning electron microscopy (SEM). The result of this study implies that the treatment of pyrite containing material with the Na-OAc buffer and Na-silicate solution reduces the generation of acid drainage.

Osmotin purified from the latex of Calotropis procera: Biochemical characterization, biological activity and role in plant defense

A protein, similar to osmotin- and thaumatin-like proteins, was purified from Calotropis procera (Ait.) R.Br latex. The isolation procedure required two cation exchange chromatography steps on 50mM Na-acetate buffer (pH 5.0) CM-Sepharose Fast Flow and 25 mM Na-phosphate buffer (pH 6.0) Resource-S, respectively. The protein purity was confirmed by an unique N-terminal sequence [ATFTIRNNCPYTIWAAAVPGGGRRLNSGGTWTINVAPGTA]. The osmotin (CpOsm) appeared as a single band (20,100 Da) in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and as two spots in two-dimensional electrophoresis (pI 8.9 and 9.1). Both polypeptides were further identified by mass spectrometry as two osmotin isoforms with molecular masses of 22,340 and 22,536 Da. The CpOsm exerted antifungal activity against Fusarium solani (IC₅₀=67.0 μg mL⁻¹), Neurospora sp. (IC₅₀=57.5 μg mL⁻¹) and Colletotrichum gloeosporioides (IC₅₀=32.1 μg mL⁻¹). However, this activity was lost when the protein was previously treated with a reducing agent (DTT, Dithiothreitol) suggesting the presence of disulfide bounds stabilizing the protein. The occurrence of osmotin in latex substantiates the defensive role of these fluids.

An adaptable HPLC method for the analysis of frequently used antibiotics in ocular samples

Four different antibiotics, delivered individually to rabbit eyes via hydrophilic intraocular lenses soaked in the drug solution prior to implantation, were measured in aqueous and vitreous humor samples from the eyes. To meet this analytical need, we developed a sensitive, high performance liquid chromatographic (HPLC) method for measuring the concentrations of moxifloxacin, gatifloxacin, linezolid, and cefuroxime in the ocular tissue. Separations were carried out on a LichroSpher RP-18 column, maintained at room temperature. The fluoroquinolones were eluted with a mobile phase consisting of 20% acetonitrile, in 0.1% trifluoroacetic acid (pH 3.0) with 30 mM tetrabutylammonium chloride. Linezolid and cefuroxime were eluted with 25% acetonitrile in 25 mM Na acetate buffer, pH 5.0. All elutions were isocratic. With ultraviolet detection, the lower limit of quantitation (LLOQ) for these compounds approached 1 ng (on-column injection). By using fluorescence detection, the LLOQ for the fluoroquinolones improved to 200 pg. The overall accuracy of the method was ≥90%. With minor modifications, the method was optimized for each of the agents, and the resulting analytical sensitivity made the method suitable for clinical investigations of the ocular penetration of these drugs.

Phosphorus Forms in Conventional and Organic Dairy Manure Identified by Solution and Solid State P‐31 NMR Spectroscopy

Organic dairy production has increased rapidly in recent years. Organic dairy cows (Bos taurus) generally eat different diets than their conventional counterparts. Although these differences could impact availability, utilization, and cycling of manure nutrients, little such information is available to aid organic dairy farmers in making nutrient and manure management decisions. In this study, we comparatively characterized P in organic and conventional dairy manure using solution and solid state (31)P NMR spectroscopic techniques. Phosphorus in both types of dairy manure was extracted with water, Na acetate buffer (100 mmol L(-1), pH 5.0) plus 20 mg Na dithionite mL(-1), or 0.025 mol L(-1) NaOH with 50 mmolL(-1) EDTA. Solution NMR analysis revealed that organic dairy manure contained about 10% more inorganic phosphate than conventional dairy manure. Whereas organic dairy manure did contain slightly more phytate P, it contained 30 to 50% less monoester P than conventional dairy manure. Solid state NMR spectroscopy revealed that mono-, di-, and trivalent metal P species with different stabilities were present in the two dairy manures. Conventional dairy manure contained relatively higher contents of soluble inorganic P species and stable metal phytate species. In contrast, organic dairy manure contained more Ca and Mg species of P. These results indicate that P transformation rates and quantities should be expected to differ between organic and conventional dairy manures.

Characterization and degradation of pectin derived from Budimka apple

The characterization of apple pectin and its oligogalacturonic fractions derived from the autochthones apple variety Budimka, characteristic for central Serbia, is described in this paper. After extraction, the apple pectin was subjected to controlled enzymatic hydrolysis by polygalacturonase (PG) and pectin lyase (PL) from Aspergillus niger and then fractionated by ion-exchange column chromatography on Dowex 1X-8 (200-400 mesh). Saturated oligo?galacturonic acids, obtained by controlled hydrolysis with PG, were efficiently separated by elution with a gradient of Na acetate buffer (pH 6.0), while unsaturated oligogalacturonic acids, obtained by controlled hydrolysis with PL, were separated on the same resin, using a gradient of Na formate buffer (pH 4.7) as the eluent. The yields of the fractions with the particular degree of polymerization (DP) were also determined. The total content of neutral saccharides in the original Budimka apple pectin was detected by HPLC analysis of the 4-nitrobenzoyl derivatives of the sugar, and amounted to 5.31%. Among the neutral saccharides, contents of galactose, glucose, rhamnose, arabinose, xylose and mannose were detected.

Calorimetric and volumetric data of salting of hen egg lysozyme using NaCl solution at pH 8.8

Heat effects and densities of hen egg lysozyme in the phosphate buffer at pH 8.8 and various NaCl concentrations were determined at 25°C by LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter. The relation between the changes of the enthalpy and apparent molar volumes vs. molality of NaCl were determined. The data are discussed together with the data obtained previously for hen egg lysozyme solutions with NaCl salt in Na-acetate buffer pH 4.2.

Radiolabeling procedure, quality control and stability of 99mTc-labeled chondroitin sulfate: A new approach of targeting osteoarthritis

Chondroitin sulfate (CS) is an endogenous component of cartilage which could determine osteoarthritis after radiolabeling. Radiolabeling was performed by 99mTcO 4 −/tin method. We found that pH is a limiting factor. At pH 6.2 in 0.05 M Na acetate buffer 32.8% colloid was formed, at pH 5.0 in 0.5 M Na acetate, in our methodology only 4.7% colloid. The tracer was highly stable. We conclude that 99mTcCS could be a promising imaging agent of osteoarthritis due to simple radiolabeling and high stability.

Structure and phospholipase function of peroxiredoxin 6: identification of the catalytic triad and its role in phospholipid substrate binding

Peroxiredoxin 6 (Prdx6) is a bifunctional protein with glutathione peroxidase and phospholipase A(2) (PLA(2)) activities, and it alone among mammalian peroxiredoxins can hydrolyze phospholipids. After identifying a potential catalytic triad (S32, H26, D140) from the crystal structure, site-specific mutations were used to evaluate the role of these residues in protein structure and function. The S32A mutation increased Prdx6 alpha-helical content, whereas secondary structure was unchanged by mutation to H26A and D140A. Lipid binding by wild-type Prdx6 to negatively charged unilamellar liposomes showed an apparent rate constant of 11.2 x 10(6) M(-1) s(-1) and a dissociation constant of 0.36 microM. Both binding and PLA(2) activity were abolished in S32A and H26A; in D140A, activity was abolished but binding was unaffected. Overoxidation of the peroxidatic C47 had no effect on lipid binding or PLA(2) activity. Fluorescence resonance energy transfer from endogenous tryptophanyls to lipid probes showed binding of the phospholipid polar head in close proximity to S32. Thus, H26 is a site for interfacial binding to the liposomal surface, S32 has a key role in maintaining Prdx6 structure and for phospholipid substrate binding, and D140 is involved in catalysis. This putative catalytic triad plays an essential role for interactions of Prdx6 with phospholipid substrate to optimize the protein-substrate complex for hydrolysis.

Complexation Thermodynamics of Cucurbit[6]uril with Aliphatic Alcohols, Amines, and Diamines

Using the isothermal calorimetric titration technique, we determined the stability constants (K), reaction enthalpy (ΔH°), and entropy (ΔS°) for complexation of cucurbit[6]uril (CB[6]) with a series of aliphatic alcohols, mono- and diamines, as well as spermidine and spermine, in aqueous solutions of alkali metal chlorides. The K for spermine reached 5.4 × 1010 M− 1 in 0.2 M LiCl, which is the largest amongst the values reported for CB[6]. Propylamine forms the strongest 1:1 complex with CB[6] (K = 21000 M− 1) in 0.1 M Na acetate buffer, which is driven exclusively by entropy. A comparison of K for 1,3-propanediamine versus 1,4-butanediamine reveals an extraordinary >60000-fold enhancement in affinity, which is the largest increment/CH2 ever observed in supramolecular chemistry. The present results in combination with our ESI-MS data reported recently unambiguously demonstrate that CB[6] exists in aqueous solution of alkali metal salts exclusively as a dicationic species, e.g. [CB[6]·2Na]2+.

Potentiometric study of quinohemoprotein alcohol dehydrogenase immobilized on the carbon rod electrode

Enzymes, which exhibit redox properties and are able to directly exchange electrons with conducting materials, are currently of special interest in the fields of biosensorics and bioelectronics. The detection of new electronic properties makes them even more attractive for these growing fields. Quinohemoprotein alcohol dehydrogenase (QH-ADH) from Gluconobacter sp. 33 was demonstrated as ‘nano-sized electrical power generator’ able to separate the electrical charges and generate a measurable electrical potential. This phenomenon was investigated potentiometrically in electrochemical system where QH-ADH was applied as the catalyst oxidizing ethanol thereby converting the energy of this chemical reaction to an electrical potential. A basic immobilization technique based on cross-linking with glutaraldehyde was applied for the immobilization of QH-ADH onto a carbon rod. The maximal open circuit potential generated by QH-ADH immobilized on carbon rod electrode was −115 mV versus an inactivated QH-ADH-modified electrode (Inactiv-ADH/carbon). If 10 mM of redox mediator K 3[Fe(CN) 6] was added to the solution the potential rose to −190 mV versus Inactiv-ADH/carbon. The influence of concentration of Na acetate buffer, pH 6.0, on registered potential was approximately at the same level as the influence of KCl concentration (influence of ionic strength). This result implies that local pH changes do not play a significant role in the development of QH-ADH-modified carbon electrode potential. The potentiometric signal was more stable than amperometric signal based on the same QH-ADH-modified carbon electrode. The ability to directly generate electric potential opens new opportunities for the application of QH-ADH and other direct electron transfer exhibiting enzymes in the design of new potentiometric sensors, biofuel cells and self-powering bioelectronic devices.

Calorimetric and volumetric data of nucleating bovine albumin solutions at various NaCl, Li2SO4 and (NH4)2SO4 concentrations

Heat effects and densities of bovine albumin solutions in Na-acetate buffer pH 4.2 at various NaCl, Li2SO4 and (NH4)2SO4 concentrations were determined by a LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter (25°C). The density measurements were made after 1 and 48 h of the dissolution of bovine albumin in the buffer. The correlations between the changes of the enthalpy of salting and apparent molar volumes vs. concentrations of salts were determined.

Production and purification of refolded recombinant Plasmodium falciparum β-ketoacyl-ACP reductase from inclusion bodies

A recombinant form of Plasmodium falciparum β-ketoacyl-ACP reductase (PfFabG) was overexpressed in Escherichia coli BL-21 codon plus (DE3). The resulting insoluble inclusion bodies were separated from cellular debris by extensive washing with buffer containing 0.05% Tween 20 and solubilized by homogenization with 8 M urea. Attempts to refold PfFabG from solubilized inclusion bodies employing Rotofor (separation based on different p Is of proteins in a mixture) followed by Ni 2+ or cation exchange chromatography were not successful either by bringing down the urea concentration instantaneously, stepwise, or by dialysis. Denatured PfFabG was therefore initially purified by cation exchange chromatography and was then correctly refolded at a final concentration of 100–200 μg/ml in a 20 mM Na-acetate buffer, pH 5.3, with 300 mM NaCl, 10% glycerol, and 0.05% Tween 20. The protein was found to be properly folded only in the presence of the cofactor NADPH and salt at a concentration ⩽300 mM by drop dilution method at 2–8 °C for 12 h. The purified final product was >98% pure by denaturing gel electrophoresis. The purified protein was biologically active in a standard enzymatic assay using acetoacetyl-CoA as a substrate. The enzyme was found to be stable up to fourth day of purification and glycerol was found to stabilize enzyme activity for several weeks, during storage. This effort paves the way for elucidation of the structure–function correlations for PfFabG as well as exploration of the enzyme for developing inhibitors against it for combating malaria.

Ni2+ binds to active site of hen egg-white lysozyme and quenches fluorescence of Trp62 and Trp108

We found that the maximum emission of the tryptophyl fluorescence of hen egg-white lysozyme is shifted from 337 to 323nm and quenched to the extent of 55% with an increase in concentrations of NiCl2 from 0 to 2M in 50mM Na acetate buffer (pH 4.7). In contrast, NaCl does not influence the fluorescence of lysozyme up to 2M. To elucidate the particular effects of Ni2+ on the tryptophyl fluorescence of lysozyme, we have measured the assembly behavior and secondary structure of lysozyme in various concentrations of NiCl2, and determined the structures of lysozyme crystals grown in 0.3, 0.5, and 1.0M NiCl2, respectively. The results of analytical centrifugation and circular dichroism experiments show that lysozyme keeps a monomer state and has an identical secondary structure, irrespective of NiCl2 concentrations. The crystal structures show that all crystals grown in different concentrations of NiCl2 have an identical main chain and side chain conformation. And one Ni2+ binding with Oδ atom of Asp52 in the active site and coordinating with five water molecules to form hexagonal coordination has been determined for each crystal structure. Based on these results, we have proposed that Ni2+ quenches the fluorescence of Trp62 and Trp108 due to the binding of Ni2+ to the active site of lysozyme.

Comparison of enthalpy and apparent molar volume data on nucleating lysozyme solution at various Li 2SO 4, MgCl 2 and (NH 4) 2SO 4 concentrations

Heat effects and densities of lysozyme solutions in Na-acetate buffer pH 4.2 at various Li 2SO 4, MgCl 2 and (NH 4) 2SO 4 concentrations were determined by an LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter (25 °C). The calorimetric measurements were carried out through mixing equal volumes of the solutions to be investigated. The density measurements were made after 1, 24 and 48 h of the dissolution of lysozyme in the buffer and electrolyte studied. Changes of nucleation enthalpy and apparent molar volumes vs. concentration of electrolyte studied have similar course.

Iron-binding ability of melanoidins from food and model systems

Soluble high molecular weight fractions isolated from the development of the Maillard reaction in 22 different model systems and food matrices were studied in order to assess their iron-chelating ability in vitro. Melanoidins and iron were incubated in a Na-acetate buffer (0.1 M, pH 5) at different weight ratios and free iron was measured by FAAS and the bathophenantroline procedure at the steady state. Melanoidins were classified at three levels according to their number of co-ordination sites for iron. Melanoidins from coffee (medium roasted), different types of beer (Pilsener, Abbeys, and dry-stout styles), and sweet wine (Pedro Ximenez) exerted a low iron-binding effect compared with melanoidins from model systems. The type of sugar was shown to be a significant parameter for obtaining melanoidins with high iron ability, and glucose was more efficient than lactose. No relationship was observed between browning and iron binding ability of melanoidins from model systems. The chromophoric residues were not the main co-ordination sites for iron complexation in the melanoidin structure.

04/00306 Potential synergies and challenges in refining cellulosic biomass to fuel, chemicals, and power: Wyman, C. E. Biotechnology Progress, 2003, 19, (2), 254–262

The enzymatic hydrolysis of wheat straw was carried out in bi-phasic media prepared with acetate esters and Na-acetate buffer. The volume percentage of the organic chemicals was 75%. The biomass was pretreated in a steam explosion plant at 217°C and for 3 min. A cellulase complex from commercial source was utilised and the experiments were run at 45°C and at constant enzyme to biomass weight ratio (0.06). Biomass loadings ranged from 6.25 to 100 g per litre of reactor. The amount of glucose formed per litre of reactor and hour and the glucose yield (grams of product per gram of biomass) were close to the values attained in pure buffer. The glucose concentration in the aqueous phase was in bi-phasic media much higher than in pure buffer and reached the value of 146 g lH2O−1 during 72 h of saccharification. The results were poorly dependent on the physical–chemical properties of the solvents. Nevertheless, butyl acetate could be slightly preferred to propyl and i-amyl acetate. The use of bi-phasic media did not require stirring rate higher than in pure buffer. The presence of acetate ester traces did not alter markedly the production of ethanol in the fermentation stage, but determined the extension of the lag phase.

Purification and molecular mass determination of a lipid transfer protein exuded from Vigna unguiculata seeds

Plants exude a variety of substances through their surface especially of roots and germinating seeds. Some of these released compounds seem to have an inhibitory action against certain pathogens. Lipid transfer proteins (LTPs) are 9 kDa cysteine-rich cationic peptides and are thought to play a role in the protection of plants against microbial infections. The aim of this work was to isolate and determine the molecular mass of a LTP present in the exudates of imbibed cowpea seeds. For exudation induction, 50 seeds were submerged in 50 mL sterile 100 mmol.L-1 Na-acetate buffer, pH 4.5 and shaken at 30 ºC for 24 h. The resulting exudate was subjected to ammonium sulphate fractionation and the pellet formed between 0 and 70 % saturation was dialysed and recovered by freeze drying. Further purification steps were carried out using chromatographic methods and the molecular mass of the LTP determined. All of these steps were monitored by SDS-Tricine gel electrophoresis and Western blotting using an anti-LTP serum. The purified LTP showed a relative molecular mass of 9 kDa.