These layers are separated by the dimethylformamide solvent molecules which are firmly anchored via a short O—H O hydrogen bond [O Aminobenzoate modified MgAl hydrotalcites as a novel smart additive of reinforced concrete for anticorrosion applications.
Corrosion of alloy C in organic acid solutions. Electrochemical studies such as cyclic potentiodynamic polarization CPP and electrochemical impedance spectroscopy EIS were performed to determine the corrosion behavior of Alloy 22 N in 1M NaCl solutions at various p H values from acidic to neutral at 90 C degrees. All the tested material was wrought Mill Annealed MA. Tests were also performed in NaCl solutions containing weak organic acids such as oxalic, acetic, citric and picric acids.
Results show that the corrosion rate of Alloy 22 was significantly higher in solutions containing oxalic acid than in solutions of pure NaCl at the same p H. Citric and Picric acids showed a slightly higher corrosion rate, and Acetic acid maintained the corrosion rate of pure chloride solutions at the same p H. Organic acids revealed to be weak inhibitors for crevice corrosion. Higher concentration ratios, compared to nitrate ions, were needed to completely inhibit crevice corrosion in chloride solutions.
Results are discussed considering acid dissociation constants, buffer capacity and complex formation constants of the different weak acids. The study of 2-acetylaminotoluene ozonolysis in acetic ACID.
The kinetics and mechanism of ozone reaction with 2-aminotoluene and its acylated derivative in acetic acid were studied in order to determine the possibility of obtaining 2- aminobenzoic acid. It is shown that the 2-aminotoluene ozonolysis reaction in acetic acid solution runs at high speed, and preferably on the free electron pair of the amino group to form mainly resinous compounds; oxidation products by the methyl group of the substrate are not formed under these conditions.
The ozone attac Effect of ultraviolet light absorbers on photostabilization of azadirachtin-A in solution part: II. The effect of photostabilization of azadirachtin-A Aza-A was examined in solutions when exposed to UV radiation, in the presence of four structurally different UV absorbers namely, p-aminobenzoic acid , 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone and phenyl salicylate.
The percentages of Aza-A recovered from the solutions after 6 h exposed to UV radiation in the presence and absence of UV absorbers indicated that the order of stabilization of Aza-A by these absorbers was similar to that obtained in the solid phase experiments in accordance with our previous observations.
It is observed that the addition of phenyl salicylate in Aza-A in mole ratio provides the excellent photostabilization of Aza-A molecule in solid phase as well as in solution among the four absorbers studied. Crystal structures of three anhydrous salts of the Lewis base 1,8-diazabicyclo[5. Full Text Available The anhydrous salts of the Lewis base 1,8-diazabicyclo[5.
Ocarboxyl hydrogen bond [2. In I, structure extension is through amine N—H Ocarboxyl hydrogen bonds between the PABA anions, giving a three-dimensional structure. O hydrogen bonds, giving in both overall two-dimensional layered structures lying parallel to O carbonyl hydrogen bond. Three-molecule aggregates are formed via O—H N pyridyl hydrogen bonds, and these are connected into supramolecular layers in the bc plane by N—H NIR spectroscopic properties of aqueous acids solutions.
Acid content is one of the important quality attributes in determining the maturity index of agricultural product, particularly fruits.
Despite the fact that much research on the measurement of acidity in fruits through non-destructive spectroscopy analysis at NIR wavelengths between to 1, nm has been conducted, the same response towards individual acids is not well known. This paper presents NIR spectroscopy analysis on aqueous citric, tartaric, malic and oxalic solutions through quantitative analysis by selecting a set of wavelengths that can best be used to measure the p H of the solutions. The most important wavelengths for p H are located at nm and nm, while at nm for water.
Study of the growth and pyroelectric properties of TGS crystals doped with aniline-family dipolar molecules. TGS crystals doped with aniline-family dipolar molecules aniline, 2- aminobenzoic acid , 3- aminobenzoic acid , 3-aminobenzene-sulphonic acid , 4-aminobenzenesulphonic acid and 4-nitroraniline have been grown by the slow-cooling solution method.
The influence of these dopants on the growth habits, crystal morphology pyroelectric properties, and structure parameters of TGS crystals has been systematically investigated. The effects of the domain structure of the seed crystal on the pyroelectric properties of the doped crystals have been studied. It is found that the spontaneous polarization P , pyroelectric coefficient lambda , and internal bias field of the doped crystals are slightly higher than those of the pure TGS, and the larger the dipole moment of the dopant molecule, the higher the P and lambda of the doped TGS crystal.
Electrochemical behavior and assembly of tetranuclear Dawson-derived sandwich compound [Cd4 H2O 2 As2W15O56 2] on 4- aminobenzoic acid modified glassy carbon electrode. Its redox electrochemistry has been studied in acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. The electrocatalytic activities of the multilayer films containing As 4 W 30 Cd 4 have been investigated on the reduction of three substrates of important analytical interests, NO 2 - , BrO 3 - and IO 3 -.
And with the increase of the number of As 4 W 30 Cd 4 layers, the catalytic current towards the reduction of BrO 3 - was enhanced and the catalytic potential shifted positively. Para- aminobenzoic acid PABA used as a marker for completeness of 24 hour urine: effects of age and dosage scheduling. Also, with the currently recommended dosage schedule PABA taken with the main meals the risk of false-positive 24 h urine collections prevails.
With refinement of the PABA test procedure, ie employing a specific analytical method Objective: To examine the age dependency of the urinary para- aminobenzoic acid PABA excretion, and if a delayed PABA excretion can be overcome by advancing intake schedule; and to examine the recovery of PABA in fractionated urinary samples collected during 24 h after single and repeated doses Subjects: Employees and relatives from the Danish Food Administration.
Setting: Ninety-nine healthy The cation is linked by N—H The chains are further connected into a three-dimensional network by N—H O hydrogen-bonding interactions involving the perchlorate anion, the water molecules and the 4- aminobenzoic acid molecules. The O atoms of the perchlorate anion are disordered over two sets of positions, with refined site occupancies of 0. The compounds obtained are identified by chemical analysis and roentgenographically.
Their solubility products, which are values of the order of 10 -9 , are determined. Behavior of copper in acidic sulfate solution : Comparison with acidic chloride.
Tromans, D. The anodic polarization behavior of copper in a 0. Interpretation of the behavior was aided by comparison with aqueous equilibria and polarization studies of copper in a 0. Metal extraction by alkyl substituted diphosphonic acids. Part 1.
P,P '-Di 2-ethylhexyl methanediphosphonic acid. An investigation of the extraction of alkaline earth cations, Fe and representative tri-, tetra- and hexavalent actinide ions from nitric acid solutions into o-xylene solutions of H 2 DEH[MDP] at different concentrations was performed. With a few exceptions, the acid dependencies of the extraction of the above metal species strongly resembles those measured in the uptake of the same metals by the chelating ion exchange resin Diphonix R , which contains gem-diphosphonic acid groups chemically attached to a polymeric matrix.
With Fe and the actinides, variable slopes of the extractant dependencies were measured, their values being strongly dependent on the acidity of the aqueous phase. N pyridyl hydrogen bonds and these are connected into supramolecular layers in the bc plane by N—H Acid -base equilibrium in aqueous solutions of 1,3-dimethylbarbituric acid as studied by 13C NMR spectroscopy.
The signals in the spectra recorded for solutions of p H p H variation have been observed for the parent barbituric acid. Crystal and molecular structure of eight organic acid -base adducts from 2-methylquinoline and different acids. Eight supramolecular complexes with 2-methylquinoline and acidic components as 4- aminobenzoic acid , 2- aminobenzoic acid , salicylic acid , 5-chlorosalicylic acid , 3,5-dinitrosalicylic acid , malic acid , sebacic acid , and 1,5-naphthalenedisulfonic acid were synthesized and characterized by X-ray crystallography, IR, mp, and elemental analysis.
All of the complexes are organic salts except compound 2. All supramolecular architectures of involve extensive classical hydrogen bonds as well as other noncovalent interactions. The results presented herein indicate that the strength and directionality of the classical hydrogen bonds ionic or neutral between acidic components and 2-methylquinoline are sufficient to bring about the formation of binary organic acid -base adducts. The role of weak and strong noncovalent interactions in the crystal packing is ascertained.
These weak interactions combined, the complexes displayed 2D-3D framework structure. O hydrogen bonding.
Condensed, solution and gas phase behaviour of mono- and dinuclear 2,6-diacetylpyridine dap hydrazone copper complexes probed by X-ray, mass spectrometry and theoretical calculations. The complexes were synthesized from two widely used diacetylpryridine dap ligands, i. Theoretical calculations DFT were used to predict the complex geometries of these new structures, their equilibrium in solution and energies associated with the transformations. Proton magnetic resonance studies in solutions of o- and p -hydroxy benzoic acids in dioxan.
In the solution of OHBA in dioxan the chemical shift of the proton of the hydroxyl group increases with increase of solute concentration and attains a maximum at a solute concentration of 0.
For the carboxyl group, the chemical shift increase with increase of solute concentration and attians a maximum at 0. In solutions of PHBA in D the chemical shift of the single line observed increases with increase of solute concentration and attains a maximum at a solute concentration of 0.
The proton magnetic relaxation studies in the above solutions also confirm the above findings. Radiation protection by ascorbic acid in sodium alginate solutions. Aliste, A. E-mail: ajaliste ipen. Alginates are gelling hydrocolloids extracted from brown seaweed used widely in the nourishing and pharmaceutical industries. As alginic acid gellification retard food entrance in the stomach alginate is an additive used in diets.
The solutions were irradiated with doses up to 10 kGy. Ascorbic acid behaved as an antioxidant against radiation oxidative shock in this model system of an irradiated viscous solution. Besides its radiation protective role on alginate solutions ascorbic acid promoted a viscosity increase in the range of concentrations employed. The objective of this work was to study the protective action of the ascorbic acid in alginate solutions against the action of 60 Co gamma radiation.
This new hybrid material exhibit a linear correlation between the ligand content of the starting TiO2 and the rhodium loading, showing the accessibility of all surfaces amines fonctions on the non-porous parent materials. New immobilized catalysts show interesting activity in cyclohexene hydroformylation.
Two molecules of bza and two molecules of bpy are connected via O—H N, N—H O hydrogen bonds, forming forming infinite double-stranded zigzag chains along the c axis. The third molecule of bpy is linked to the chain by weak C—H These sheets are stacked via C—H Study of free acidity determinations in aqueous solution.
The object of this work is the study of the principal methods which can be applied to the measurement of 'free' acidity. In the first part, we define the various types of acidity which can exist in aqueous solution ; then, after having studied some hydrolysis reactions, we compare the value of the neutralisation p H of the hydrated cation and that of the precipitation of the hydroxide. In the second part we have started to study the determination of the acidity of an aqueous solution.
After having rapidly considered the 'total' acidity determination, we deal with the problem of the 'free' acidity titration.
We have considered in particular certain methods: extrapolation of the equivalent point, colorimetric titrations with or without a complexing agent, and finally the use of ion-exchange resins with mixed aqueous and solvent solutions. Rare earth and zinc layered hydroxide salts intercalated with the 2- aminobenzoate anion as organic luminescent sensitizer.
The results from FTIR spectroscopy suggest a direct coordination of 2- aminobenzoate to the metal cations of the inorganic layered structure. The organic derivative products from the intercalation reactions absorb a broader range of UV-light in relation to that shown by the parent material; the photoluminescence measurements present a strong violet, blue and green luminescence under UV-light excitation for layered compounds with, Zn, Y and Tb, respectively.
Rare earth hydroxide salts RE-LHS are potential alternative matrices for the immobilization of organic species to produce luminescent materials. Cursino, Ana Cristina Trindade, E-mail: anacursino ufpr. Box , Curitiba, PR Brazil. Estimation of free acid content in lanthanide salt solution used for p H-potentiometric determination of their stability constants with organic ligands. To improve the p H-potentiometric method for determining complex stability constants the possibility of alkalimetric titration of a free acid in the lanthanide perchlorate solution after binding metal ions by disodium salt of ethylene-diamine-tetraacetic acid is studied.
The stability constants were determined from the difference between the total acid content after complexon addition and doubled metal cation content in the solution which has been preliminarily determined by the complexonometric method.
It is shown that the alkaline NaOH equivalent quantities spent for free acid titration either in the absence or presence of the complexon is different. With increase of free acid content in the solution the difference in determinations with complexon and without it is somewhat reduced. Thus, the use of complexon contributes to a higher accuracy in determining the free acid , and in the first place in case of minor contents.
Determination of free nitric acid in uranyl nitrate solution. Potentiometric titration of uranyl nitrate solution with sodium hydroxide exhibits two peaks. This reaction, indicating the partial hydrolysis of uranyl oxalate complex, appears to be complete at p H9. If the titration is carried out to this end-point p H, the total alkali consumed can be equated to the sum of uranium content and the free acidity present in the sample volume. Based on this, a method was standardised to determine the free acidity in uranyl nitrate solution.
The sample, taken in a solution of potassium oxalate previously adjusted to p H9, is titrated to this p H with standard sodium hydroxide. The free acidity in the sample can be computed by subtracting the alkali reacted with uranium from the total alkali consumed. Analyses of several synthetic samples containing uranium and nitric acid in a wide range of combinations indicate that the free acidity can be accurately determined by this method, if uranium concentration in the sample is known.
The results are compared to those obtained by two other widely used methods, viz. The advantages of and the precision obtained with the present method over the above two methods are discussed. The acid -base chemistry of three zwitterionic compounds, namely anthranilic 2- aminobenzoic acid , N -methylanthranilic and N -phenylanthranilic acid has been characterized in terms of the macroconstants K a1 , K a2 , the isoelectric point p H I , the tautomerization constant K z and microconstants k 11 , k 12 , k 21 , k The potentiometric titration method was used to determine the macrodissociation constants.
The Yasuda-Shedlovsky extrapolation procedure has been used to obtain the values of p K a1 and p K a2 in aqueous solutions. The p K a1 and p K a2 values obtained by this method are 2.
The method uses spectral differences between the zwitterionic form found at isoelectric p H in aqueous solution and the unionized form formed in an organic solvent of low dielectric constant. The values of log 10 K z for anthranilic and N -phenylanthranilic acids are similar and have values of 0.
The results indicate that the tested compounds, in aqueous solution around the isoelectric point p H I , occur mainly in the zwitterionic form. Moreover, the influence of the type of substituent and p H of the aqueous phase on the equilibrium were analyzed with regard to the formation and the coexistence of different forms of the acids in the examined systems.
Soil solution interactions may limit Pb remediation using P Lead Pb contaminated soils are a potential exposure hazard to the public. Amending soils with phosphorus P may reduce Pb soil hazards. Soil was acidified, neturalized and re-acidified to encourage Pb phosphate formation. PRSTM-probes were used to evaluate changes in soil solution chemistry. Treatments increased soil electrical conductivity above 16 mS cm-1, potentially causing a new salinity hazard.
This study used a novel approach by combining the human ingestion endpoint, PRSTM-probes, and X-ray absorption spectroscopy to evaluate treatment efficacy.
Identification of a 23 kDa protein from maize photoaffinity-labelled with 5-azido-[H]indolylacetic acid. A 23 kDa protein p 23 was identified in microsomal extracts from maize coleoptiles by photoaffinity labelling with 5-azido-[H]indolylacetic acid [3H]N3IAA.
In addition, labelling was efficiently decreased by tryptophan, as well as by the scavenger p-aminobenzoic acid. Labelling was, however, not affected by synthetic auxins such as 1-naphthylacetic acid or 2,4-dichlorophenoxyacetic a Investigation of the luminescent properties of terbium-anthranilate complexes and application to the determination of anthranilic acid derivatives in aqueous solutions. The luminescent properties of terbium complexes with furosemide FR , flufenamic FF acid , tolfenamic TF acid and mefenamic MF acid have been investigated in aqueous solutions.
For all four compounds, complexation occurs when the carboxylic acid of the aminobenzoic group is dissociated and is greatly favoured in the presence of trioctylphosphine oxide as co-ligand and Triton X as surfactant.
The sensitivity of the method for the determination of anthranilic acid derivatives is improved by one to two orders of magnitude with respect to that achieved using native fluorescence or terbium-sensitised luminescence in methanol. The method has been applied to the determination of flufenamic acid in spiked calf sera with and without sample pretreatment. Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions.
The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and p H of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant.
It is found that the inflection point on the dependence of the difference between the p H values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of p H of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.
The passivation of calcite by acid mine water. Column experiments with ferric sulfate and ferric chloride solutions at p H 2.
Soler, Josep M. Column experiments, simulating the behavior of passive treatment systems for acid mine drainage, have been performed. The composition of the solutions was monitored during the experiments. At the end of the experiments passivation of the columns , the composition and structure of the solids were measured. However, after some time several weeks, depending on the conditions , the columns became chemically inert.
The results showed that passivation time increased with decreasing anion and metal content of the solutions. Schwertmannite and goethite appeared as the Fe III secondary phases in those experiments. The photochemistry of periodate and periodic acid in aqueous solution was studied i by quantum yield measurements at low light intensity ii by flash photolysis, and iii by photolysis of glassy samples at 77 K.
The photochemical studies were supplemented with pulse radiolysis studies In strongly alkaline solution the photodecomposition of periodate proceeds via formation of O— and IVI. At p H solution O3 P is formed in a small Effects of solution P H on the adsorption of aromatic compounds from aqueous solutions by activated carbon. Absorption of p -Cresol, Benzoic acid and Nitro Benzene by activated carbon from dilute aqueous solutions was carried out under controlled ph conditions at k.
In acidic conditions, well below the p K a of all solutes , it was observed that the adsorbate solubility and the electron density of its aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces.
In higher solution ph conditions, on the other hand, it was found that the electrostatic forces played a significant role on the extent of adsorption. The Effect of ph must be considered from its combined effects on the carbon surface and on the solute molecules. It was found that the uptake of the molecular forms of the aromatic solutes was dependent on the substituents of the aromatic ring. Adsorption of the solutes in higher P H values was found to be dependent on the concentration of anionic form of the solutes.
All isotherms were fitted into Freundlich Isotherm Equations. N-glycans of therapeutic glycoproteins are critical quality attributes that should be monitored throughout all stages of biopharmaceutical development.
To reduce both the time for sample preparation and the variations in analytical results, we have developed an N-glycan analysis method that includes improved 2- aminobenzoic acid 2-AA labeling to easily remove deglycosylated proteins. The structures of 15 major and 18 minor N-glycans were identified from their mass values determined by quadrupole time-of-flight MS.
Taken together, the results show that a wide repertoire of N-glycans of therapeutic glycoproteins can be analyzed with high efficiency and consistency using the improved 2-AA labeling-based N-glycan analysis method. Crystal structures of two erbium III complexes with 4- aminobenzoic acid and 4-chloronitrobenzoic acid. The Er—O bond-length range is 2. Er separation in the dinuclear complex unit is 4. One of the coordinating water molecules is involved in an intra-unit O—H O hydrogen-bonding association with an inversion-related carboxylate O-atom acceptor.
The latter provides the inter-unit link in the one-dimensional coordination polymer extending along []. The Er—O bond-length range in II is 2. Er separation within the dinuclear unit is 4. In the crystal of I, extensive inter-dimer O—H O and N—H O hydrogen-bonding interactions involving both the coordinating water molecules and the solvent water molecules, as well as the amine groups of the 4-ABA anions, give an overall three-dimensional network structure.
Quantum chemical calculations and experimental investigations on 2- aminobenzoic acid -cyclodiphosph V azane derivative and its homo-binuclear Cu II complex. It also confirms that nitrogen atom of the pyridine ring contribute to the complexation. Electronic spectra and magnetic susceptibility measurements reveal square-planar geometry for the Cu II complex. Quantum chemical calculations were utilized to explore the electronic structure and stability of the H4L as well as the binuclear Cu II complex.
Different tautomers and geometrical isomers of the ligand were optimized at the ab initio DFT level. Simulated IR frequencies were scaled and compared with that experimentally measured. Arsenic removal from acidic solutions with biogenic ferric precipitates.
As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at p Hremoves iron and arsenic from acidic solutions , indicating potential for mining wastewater treatment. Synthesis, thermal, spectral, and biological properties of zinc II 4- aminobenzoate complexes.
The variation in mobile phase p H and ionizable solute dissociation constant p K a with the change of organic modifier fraction in hydroorganic mobile phase has seemingly been a troublesome problem in studies and applications of reversed phase high performance liquid chromatography RP-HPLC.
Most of the early studies regarding the RP-HPLC of acid -base compounds have to measure the actual p H of the mixed mobile phase rigorously, sometimes bringing difficulties in the practices of liquid chromatographic separation.
The theoretical and experimental derivation revealed that the variation in mobile phase p H and solute p K a will not affect the QSRRs of acidic compounds. This conclusion is proved to be suitable for various types of ion-suppressors, i. Although different types of ion-suppressor all can be used as mobile phase p H modifiers, the QSRR model obtained by using perchloric acid as the ion-suppressor was found to have the best result, and the slightly inferior QSRRs were obtained by using acetic acid or PBS as the ion-suppressor.
Process for extracting uranium from phosphoric acid solutions. The description is given of a method for extracting uranium from phosphoric acid solutions whereby the previously oxided acid is treated with an organic solvent constituted by a mixture of dialkylphosphoric acid and trialkylphosphine oxide in solution in a non-reactive inert solvent so as to obtain de-uraniated phosphoric acid and an organic extract constituted by the solvent containing most of the uranium.
The uranium is then separated from the extract as uranyl ammonium tricarbonate by reaction with ammonia and ammonium carbonate and the extract de-uraniated at the extraction stage is recycled. The extract is treated in a re-extraction apparatus comprising not less than two stages. The extract to be treated is injected at the top of the first stage. At the bottom of the first stage, ammonia is introduced counter current as gas or as an aqueous solution whilst controlling the p H of the first stage so as to keep it to 8.
Folates belong to the B vitamin group based on the parental compound folic acid FA. They are involved in important biochemical processes like DNA synthesis and repair. FA is composed of a pteridine ring, p-aminobenzoic acid and glutamate moieties. The human metabolism is not able to synthesize folates and therefore obtain them from diet. FA, a synthetic vitamin, is used as a food fortificant because of its low price, relative stability and increased bioavailability compared to natural folate forms.
FA is known to be a sensitive compound easily degradable in aqueous solution by ultraviolet and visible light towards various by-products. Irradiation is a process for preservation of foods that uses accelerated electrons, gamma rays or X-rays.
Irradiation is proposed for the treatment of various food products, eliminating or reducing pathogens and insects, increasing the storage time and replacing chemical fumigants. This study concerns the identification of degradation products of FA after E-beam irradiation.
Applied doses were between 0 control and Absorbed doses were monitored with FWT X-ray structural investigation into complexes of p-aminobenzoic acid and metals. The basis of the structure was formed by infinite along the axis a chains of strontium atom octavertices articulated with common oxygen vertices. Sr-O bond lengths were 2. Bond angles were presented. Quantitative twoplex glycan analysis using 12C6 and 13C6 stable isotope 2- aminobenzoic acid labelling and capillary electrophoresis mass spectrometry.
Capillary electrophoresis CE offers excellent efficiency and orthogonality to liquid chromatographic LC separations for oligosaccharide structural analysis. Combination of CE with high resolution mass spectrometry MS for glycan analysis remains a challenging task due to the MS incompatibility of background electrolyte buffers and additives commonly used in offline CE separations.
Here, a novel method is presented for the analysis of 2- aminobenzoic acid 2-AA labelled glycans by capillary electrophoresis coupled to mass spectrometry CE-MS. To ensure maximum resolution and excellent precision without the requirement for excessive analysis times, CE separation conditions including the concentration and p H of the background electrolyte, the effect of applied pressure on the capillary inlet and the capillary length were evaluated.
The twoplex quantitative CE-MS glycan analysis platform is ideally suited for comparability assessment of biopharmaceuticals, such as monoclonal antibodies, for differential glycomic analysis of clinical material for potential biomarker discovery or for quantitative microheterogeneity analysis of different glycosylation sites within a glycoprotein.
Additionally, due to the low injection volume requirements of CE, subsequent LC-MS analysis of the same sample can be performed facilitating the use of orthogonal separation techniques for structural elucidation or verification of quantitative performance. Modelling of the effect of solute structure and mobile phase p H and composition on the retention of phenoxy acid herbicides in reversed-phase high-performance liquid chromatography.
A feed-forward artificial neural network ANN learned by error back-propagation is used to generate a retention predictive model for phenoxy acid herbicides in isocratic reversed-phase high-performance liquid chromatography.
The investigated solutes 18 compounds , apart from the most common herbicides of this class, include some derivatives of benzoic acid and phenylacetic acid structurally related to phenoxy acids , as a whole covering a p K a range between 2. After elimination of redundant variables, a nine-dimensional model is identified and its prediction ability is evaluated by external validation based on three solutes not involved in model generation and by cross-validation.
A multilinear counterpart in terms of the same descriptors is seen to provide a noticeably poorer retention prediction. Removal of sulfamic acid from plutonium sulfamate--sulfamic acid solution. Plutonium metal can be readily dissolved in aqueous solutions of sulfamic acid. When the plutonium sulfamate--sulfamic acid solutions are added to normal purex process streams, the sulfamate ion is oxidized by addition of sodium nitrite. This generates sodium sulfate which must be stored as radioactive waste.
When recovery of ingrown Am or storage of the dissolved plutonium must be considered, the sulfamate ion poses major and undesirable precipitation problems in the process streams. If the solutions are chilled, additional sulfamic acid will precipitate. Acidity function p a H gamma Cl as a step to p H assessment. The conventional assignment of p H reference buffer standards, p H S , is achieved by means of a series of procedures that follow from measurement of Harned cell potentials for an electrolyte solution which is the buffer solution of interest.
An intermediate step is assessment of the acidity function p a H gamma Cl 0 , the extrapolated value of a linear representation of the dependence of p a H gamma Cl on m Cl for at least three different molalities, m Cl , of added alkali chloride 0. This experimental value can be compared with a theoretically expected value calculated from the dissociation constants of the buffer species.
Whereas these calculations always give negative slopes for diprotic and triprotic acids and zero slope for monoprotic acids , experimental values with negative or positive slopes can be obtained for well fitting straight lines obtained for buffer solutions with ionic strengths from 0.
Such disagreement between theoretically and experimentally obtained values introduce an extra source of uncertainty in the establishment of p H S and on its traceability chain. In this work examples are presented and discussed for which the discrepancy between expected and experimental values leads to different intercept p a H gamma Cl 0. Acetic acid extraction from aqueous solutions using fatty acids. A major challenge for production of acetic acid via bio-based routes is cost-effective concentration and purification of the acetic acid from the aqueous solutions , for which liquid—liquid extraction is a possible method.
A main challenge in extraction of acetic acid from dilute aqueous solutions is. Corrosion control of vanadium in aqueous solutions by amino acids. The electrochemical behavior of vanadium in amino acid free and amino acid containing aqueous solutions of different p H was studied using open-circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy EIS.
The corrosion current density, i corr , the corrosion potential, E corr and the corrosion resistance, R corr , were calculated. A group of amino acids , namely, glycine, alanine, valine, histidine, glutamic and cysteine has been investigated as environmentally safe inhibitors. The effect of Cl - on the corrosion inhibition efficiency especially in acid solutions was investigated. In neutral and basic solutions , the presence of amino acids increases the corrosion resistance of the metal.
The corrosion inhibition process is based on the adsorption of the amino acid molecules on the metal surface and the adsorption process follows the Freundlich isotherm. The adsorption free energy for valine on V in acidic solutions was found to be Effect of citric acid on the acidification of artificial pepsin solution for metacercariae isolation from fish.
Artificial digestive solution based on pepsin is essential for collecting metacercariae from fish. To promote the enzymatic reactivity of pepsin, the p H of the solution has to be adjusted to p H 1. Hydrochloride HCl is usually used for this purpose, but the use of HCl raises safety concerns. The aim of this work was to address the usefulness of citric acid as an alternative for HCl for the acidification of pepsin solution , and to examine its potential to damage metacercariae during in vitro digestion as compared with HCl.
Digestion of fish muscle was evaluated by measuring released protein concentrations by spectrophotometry. The present study shows that addition of citric acid reduced the p H of pepsin solutions to the required level. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. Read more about how to correctly acknowledge RSC content.
Fetching data from CrossRef. This may take some time to load. Loading related content. Jump to main content. Jump to site search. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page. Issue 13, From the journal: CrystEngComm. Martin R. Cruz-Cabeza , b Craig L. Bull , c Nicholas P. Two independent experiments were performed for each cell line. In each experiment the extract was tested in triplicate.
Cellular viability was expressed as a percentage relative to the solvent control. The Kolmogorov Smirnov test was used to check for normality distribution of data. The separation was carried out using a gradient from Nine extracts resulted in no hits in the dereplication analysis that could explain the observed activities.
These were submitted to the GNPS data analysis workflow using default parameters except ion mass tolerance precursor, which was set to 0. The resulting molecular network was visualized with Cytoscape v3. These putative compound masses were used for an additional dereplication step by searching the predicted accurate mass against the Dictionary of NP database version When hits from Actinobacteria were obtained, information regarding the biological activity of the compounds was retrieved from this database.
A total of 90 actinobacterial strains were isolated from sterilized tissue fragments obtained from the holdfast, stipe, and blades of L. Actinobacterial strains were isolated from all parts of the macroalgae Figure 1B and recovered from the three selective culture media used Figure 1C. Several strains presented typical characteristics of actinobacteria, such as slow growth, formation of hyphae and production of spores and pigments, the latter sometimes leading to a change of the color of the culture medium Figure 2.
The sterilization treatment was not entirely effective, as five isolates were recovered from the sterilization controls. Two of such isolates, identified as Pseudomonas sp. Streptomyces , Isoptericola , Rhodococcus , Nonomuraeae , Nocardiopsis , and Microbacterium strains were isolated from the holdfast, Microbispora and Microbacterium strains from the stipe, and Streptomyces and Microbacterium strains from the blades Figures 1A,B , 3.
The selective medium SCN allowed the retrieval of strains belonging to all genera identified in this study Figure 1C. Growth of Streptomyces and Microbacterium strains was observed in all culture media used.
The evolutionary relationships between the isolated actinobacterial strains was inferred from a 16S rRNA gene phylogenetic tree Figure 3. Several of the isolated strains, many of them affiliated with the genus Streptomyces , were found to group very closely in a well-supported clade, which indicates a high similarity between these strains.
Figure 1. Actinobacterial genera recovered from L. A Number of actinobacterial strains affiliated with the different genera retrieved from L. Figure 2. Morphological diversity of some actinobacterial strains isolated from L.
Figure 3. The tree was generated using bp and bootstraps. Numbers in parenthesis correspond to GenBank accession numbers. Bacillus subtilis was used as an outgroup. Antimicrobial assays identified 45 isolates capable of inhibiting the growth of C. These isolates were affiliated with the genera Streptomyces 39 strains , Isoptericola one strain , Nonomuraeae one strain , Nocardiopsis one strain , Microbispora one strain , and Microbacterium two strains.
The diameters of inhibition halos varied from 0. The MIC value was reproduced once. The lowest antibacterial MIC value was determined for S. Table 1. Actinobacteria isolated from L. Twenty-eight isolates showed statistically significant cytotoxic activity against at least one of the tested human cancer cell lines compared to the solvent control. Here, we searched for strains that had cytotoxic activities toward human cancer cell lines, but not against the normal cells.
This same pattern, albeit with lower potencies, was observed for the extracts obtained from strains KENR23D, 26, 31, 57, 71, 74, 78, and Figure 4.
The effect of extracts from actinobacterial strains isolated from L. All of these extracts were re-tested on the non-cancer cell line C for general cytotoxicity. PC and SC indicate positive and solvent controls, respectively. Interestingly, we found that 26 of these extracts contained one or more members of the antimycin family of compounds Supplementary Table S2. This allowed us to pinpoint four clusters that were observed in a single extract, which we defined as an additional criterium for an increased chance of a cluster corresponding to a novel compound.
Two of such clusters were found in the extract obtained from Streptomyces sp. KENR85, one from Streptomyces sp. KENR86 and one other from Streptomyces sp. As such, for each of these four clusters of compounds, we carried out an additional dereplication. For two of the clusters, a number of hits from Actinobacteria were retrieved Supplementary Table S3 that could explain the accurate mass and the observed activities in the corresponding extract.
However, for the remaining two clusters one from Streptomyces sp. KENR85 and one from Streptomyces sp. KENR91 , no hits were retrieved from this database.
Figure 5. The extracts obtained from three Streptomyces sp. Macroalgae offer a favorable habitat for several epiphytic and endophytic microorganisms Egan et al. Although actinobacterial endophytes of terrestrial plants have been proven to be a valuable source of bioactive compounds Strobel, ; Zhao et al. We isolated a high number of actinobacterial strains some of them possibly endophytes from the kelp L. The majority of the isolated strains was obtained from the holdfast of L.
Streptomyces strains are commonly isolated and cultured under laboratory conditions and have been isolated from numerous marine ecological niches Rashad et al. Several Streptomyces strains with biological activity have been isolated from algae, including from species belonging to the class Phaeophyceae where L.
In our study, most of the isolates recovered from L. Rare actinobacterial genera are also gaining increasing attention in the field of NP discovery, owning to their underexplored metabolic potential Subramani and Aalbersberg, , ; Dhakal et al. We isolated strains affiliated with six rare actinobacterial genera — Rhodococcus , Nonomuraeae , Microbispora , Isoptericola , Nocardiopsis , and Microbacterium. Isolates from the latter three genera have also been obtained from macroalgae species, including some from the class Phaeophyceae Hollants et al.
Half of the isolates exhibited antimicrobial activity, mostly antifungal activity against C. Streptomyces strains isolated in other studies from diverse marine sources have produced secondary metabolites with antifungal properties against C.
El-Gendy and El-Bondkly, In this study we have also isolated eight actinobacterial strains exhibiting antibacterial activity against S. Marine actinobacteria are known to produce secondary metabolites capable of inhibiting the growth of S. The compounds arenimycin and abyssomicin C are two such examples, produced by Salinispora and Verrucosispora strains, respectively Bister et al.
Recently, an actinobacterial strain identified as Kocuria marina CMG S2, isolated from the brown macroalgae Pelvetia canaliculata , was reported to produce a novel antibiotic, named as kocumarin, with activity against fungi and pathogenic bacteria, including methicillin-resistant S.
Likewise, several actinobacterial strains isolated from different marine sources, including macroalgae, are capable of producing secondary metabolites with anticancer activity Lam, ; Asolkar et al. Many of these strains are Streptomyces but genera exclusive from marine environments like Salinispora , Salinibacterium , and Marinispora are also considered promising sources of anticancer molecules Lam, ; Zotchev, In our study, a total of 28 extracts demonstrated capacity to decrease significantly the viability of the cell lines.
However, some of the extracts with strong anticancer activity had negligible toxicity to non-tumor cells, and showed specificity toward neuroblastoma cells KENR18, 25, 59, The bioassay data that we obtained indicated the presence of active compounds in the extracts and, hence, the potential for the discovery of new bioactive metabolites.
As such, and to understand to what extent the observed bioactivities could result from known compounds and, concomitantly, which extracts were more likely to harbor new bioactive metabolites, we performed dereplication and molecular networking analyses. We found that a number of different antimycins was associated with many of the dereplicated samples.
These likely antimycin-containing extracts were obtained from different genera of actinobacteria and from all sampled L. Members of this class of metabolites have been isolated previously from marine actinobacteria Imamura et al. UV-Vis and ion chromatograms extracted from the LC-HRESIMS data indicate that these potential novel metabolites are not likely to be abundant in crude extracts Figure 5 , but we intend to follow-up on these interesting results.
Moreover, we only analyzed in depth clusters from the molecular network that were associated with a single extract, which does not rule out the possibility for additional chemical novelty in the set of nine strains that showed no relevant hits in the GNPS dereplication. This work adds to the knowledge available on actinobacteria associated with marine macroalgae and their bioactive potential.
Our data indicates that the kelp forest alga L. MG and IR carried out the isolation of actinobacteria and taxonomic identification. MG and TR carried out cell line cytotoxicity assays. IA performed the kelp sampling. FP oversaw the molecular biology methodologies and performed the phylogenetic analysis together with MG.
RU oversaw cell line assays and performed the statistical analysis. MG and MC led the writing of the manuscript with contributions from all the co-authors.
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