Solutions Of L-phenylalanine Research Articles

Basic accuracy of a1D NOESY with presaturation method using standard solutions of amino and maleic acids.

1D NOESY with presaturation (NOESY-presat) is the most popular water suppression method. When D2O solutions of L-phenylalanine or L-valine were measured using NOESY, the absolute concentration biases increased with longer mixing and evolution times, reaching a maximum of 54% with respect to the preparation values. At mixing and evolution times of 0ms and 0µs, respectively, the absolute concentration biases were reduced to less than 3%. The remaining biases were caused by the off-resonance effect, which was prevented by setting the frequency offset to an intermediate value between the analyte and internal standard 3-(trimethylsilyl)-1-propanesulfonic acid-d6 (DSS-d6) signals. Nevertheless, NOESY-presat gave maximum absolute biases of 26% and 11% for glycine and maleic acid concentrations, respectively, in three H2O/D2O (90/10 vol%) solutions. The proposed NOESY-dual-presat method reduced the absolute biases to below 4%. However, water suppression was insufficient but was improved by setting the frequency offset to the same as the presaturation offset with the H2O signal, although the absolute biases rose to 5 to 13%. Quantitative analyses using NOESY-presat and NOESY-dual-presat require careful consideration of the off-resonance effect.

Enrichment of amino acids from its aqueous solution by ultrasonic atomization and ultrafine bubbles

The enrichment characteristics of amino acids by ultrasonic atomization were investigated. Samples were aqueous solutions of L-phenylalanine and L-tyrosine. The ratio of amino acid concentration in the mist to that in the solution was defined as the enrichment factor. As the flow rate of carrier gas became higher, the collection mass of mist increased and the enrichment factor decreased. The enrichment factor depended on the solution pH. The enrichment factor increased with decreasing amino acid concentration in the solution and enhanced by the addition of ultrafine bubbles.

Molecular interactions studies of doxycycline hyclate in water, aqueous L-phenylalanine and glycyl glycine at different temperatures by using volumetric, ultrasonic and viscometric parameters

The density, sound velocity and viscosity of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine have been determined at different temperatures (305.15, 310.15, 315.15 and 320.15) K. The calculated values of partial molar volume (V_ϕ^o), standard partial molar volume of transfer (〖Δ_tr V〗_ϕ^o), partial molar adiabatic compressibility (κ_(ϕ,s)^o) and partial molar adiabatic compressibility of transfer (〖Δ_tr κ〗_(ϕ,s)^o) for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine infer the dominance of ion-hydrophilic interactions over hydrophobic-hydrophobic interactions. The Jones-Dole viscosity B-coefficient, viscosity B-coefficient of transfer (ΔtrB), free energy of activation of viscous flow per mole of pure solvent (〖Δμ〗_1^(o*)) and solute (〖Δμ〗_2^(o*) ), respectively, activation entropy (〖ΔS〗_2^(o*)) and activation enthalpy (〖ΔH〗_2^(o*)) of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been calculated using viscosity data. The structure making and breaking behaviour of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine are obtained from the values of Hepler’s constant i.e.((δ^2 V_ϕ^o)/(δT^2 )) and (dB/dT). The presence and absence of caging effect has been studied with the help of partial molar adiabatic expansibility (E_ϕ^o). The isobaric thermal expansion coefficient (α^o= (E_ϕ^o)/(V_ϕ^o )), intermolecular free length and acoustic impedance for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been determined.

Scalable Treatment of Flowing Organic Liquids Using Ambient-Air Glow Discharge for Agricultural Applications

In this work, we developed a portable device with low production and operation costs for generating ambient-air glow discharge (AAGD) that is transferred to the surface of flowing liquid and demonstrated its applicability to practical use in agriculture. An experiment procedure that ensured the stable treatment of various liquids was established. Additionally, it was found that humidity did not have a significant effect on the treatment process, which makes the use of the developed device possible in various locations. It was found that an L-phenylalanine solution treated with AAGD allows simultaneous 40% hydroponic radish-sprout growth promotion with a bactericidal effect. Further, scalability and practical-application possibilities in hydroponic plant growth were discussed.

Comments on “Role of solubility and solvation thermodynamics on the stability of l-phenylalanine in aqueous methanol and ethanol solutions”

Several errors were found in the published paper by Imran and coworkers [J. Mol. Liq. 265 (2018) 693-700] pertaining to the calculation of thermodynamic properties of solution of l-phenylalanine in binary aqueous-methanol and aqueous-ethanol solvent mixtures. Errors were also found in the calculation of the Gibbs energies and entropies for transferring l-phenylalanine from water to the various aqueous-alcohol solvent mixtures.

Physico-chemical behaviour of l-phenylalanine in aqueous and aqueous d-glucose solutions at different temperatures

The density, d, viscosity, η, and the conductance, Λ, values of solutions of l-phenylalanine in aqueous and aqueous solutions of d-glucose (5, 10, 15, and 20wt%) have been determined at four different temperatures ranging from 298.15K to 313.15K at 5K intervals. Sound velocity has been measured at 298.15K. The experimental data were used to calculate apparent molar volume, Vφ, limiting apparent molar volume, Vφ°, apparent molar isentropic compressibility, Ks,φ, and limiting apparent molar isentropic compressibility, Ks,φ°. The derived acoustical and thermodynamics parameters, namely isentropic compressibility, Ks, specific acoustic impedance, Z, molar compressibility, W, molar sound velocity, R, free length, Lf, and relative association, RA, have been calculated. Shedlovsky equation has been used to obtain limiting molar conductance, Λm°, from the conductance data. The results have been discussed in terms of solute–solute, solute–solvent and solvent–solvent interactions.

Preparation and characterization of L-phenylalanine modified chitosan resin for aromatic amino acid adsorption

A novel L-phenylalanine modified chitosan resin (PCR) was prepared for adsorption of aromatic amino acid from mixed amino acids solution. The structure and properties of PCR were observed by FTIR, 13C NMR, AFM and SEM. PCR was found to swell rather than dissolve in acidic mediums from its solubility and swelling behavior experiments. Batch adsorption experiments were performed to evaluate the adsorption capacity, selectivity and reusability as well as its application to the removal of L-phenylalanine and tyrosine from mixed amino acids solution. The results indicated that the maximum adsorption capacity of PCR was 309.44 mg/g in sole L-phenylalanine solution at 25 °C. The selectivity coefficient of L-phenylalanine, tyrosine and other amino acids on PCR indicated an overall preference for L-phenylalanine and tyrosine, which were much higher than that of non-modified chitosan resin. PCR could be reused for ten times with about 6.26% loss. This suggests that PCR is a very promising adsorbent for the selective removal of aromatic amino acid from mixed amino acids solution. Open image in new window

Physicochemical study of solute–solute and solute–solvent interactions of l-phenylalanine in (water + arabinose/glucose/sucrose) solutions at different temperatures

The values of density, ρ and ultrasonic speed, u of solutions of l-phenylalanine in aqueous-carbohydrate solvents (2.5 and 5% of arabinose/glucose/sucrose, w/w in water) at T=(293.15, 298.15, 303.15, 308.15, 313.15, and 318.15)K; and viscosities, η of these solutions at (298.15, 303.15, 308.15, 313.15, and 318.15)K and at atmospheric pressure were measured. From these experimental results, the apparent molar volume, Vϕ, limiting apparent molar volume, Vϕ° and the slope, Sv, transfer volume, Vϕ,tr°, apparent molar compressibility, Ks,ϕ, limiting apparent molar compressibility, Ks,ϕ° and the slope, Sk, transfer volume, Vϕ,tr°, transfer compressibility, Ks,ϕ,tr°, limiting apparent molar expansivity, Eϕ°, Hepler’s constant, (∂2Vϕ°/dT2), Falkenhagen Coefficient, A, Jones–Dole coefficient, B and hydration number, nH were calculated. The Gibbs free energies of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, entropies, ΔS° and enthalpies, ΔH° of activation of viscous flow were also calculated and discussed in terms of transition state theory. The structure-making/breaking ability of the amino acid has also been discussed in terms of the sign of (∂2Vϕ°/dT2) and dB/dT. The results have been interpreted in terms of solute–solvent and solute–solute interactions in these systems.

A new approach for quantitative analysis of l-phenylalanine using a novel semi-sandwich immunometric assay

Here, we describe a novel method for L-phenylalanine analysis using a sandwich-type immunometric assay approach for use as a new method for amino acid analysis. To overcome difficulties of the preparation of high-affinity and selectivity monoclonal antibodies against L-phenylalanine and the inability to use sandwich-type immunometric assays due to their small molecular weight, three procedures were examined. First, amino groups of L-phenylalanine were modified by "N-Fmoc-L-cysteine" (FC) residues and the derivative (FC-Phe) was used as a hapten. Immunization of mice with bovine serum albumin/FC-Phe conjugate successfully yielded specific monoclonal anti-FC-Phe antibodies. Second, a new derivatization reagent, "biotin linker conjugate of FC-Phe N-succinimidyl ester" (FC(Biotin)-NHS), was synthesized to convert L-phenylalanine to FC-(Biotin)-Phe as a hapten structure. The biotin moiety linked to the thiol group of cysteine formed a second binding site for streptavidin/horseradish peroxidase (HRP) conjugates for optical detection. Third, a new semi-sandwich-type immunometric assay was established using pre-derivatized L-phenylalanine, the monoclonal anti-FC-Phe antibody, and streptavidin/HRP conjugate (without second antibody). Using the new "semi-sandwich" immunometric assay system, a detection limit of 35 nM (60 amol per analysis) and a detection range of 0.1-20 μM were attained using a standard L-phenylalanine solution. Rat plasma samples were analyzed to test reliability. Intra-day assay precision was within 6% of the coefficient of variation; inter-day variation was 0.1%. The recovery rates were from 92.4 to 123.7%. This is the first report of the quantitative determination of L-phenylalanine using a reliable semi-sandwich immunometric assay approach and will be applicable to the quantitative determination of other amino acids.

Enthalpies of solution of L-phenylalanine in aqueous solution of amides at 298.15 K

The enthalpies of solution ΔsolHm have been determined for L-phenylalanine in aqueous solutions of formamide (FA), N-methylformamide (MFA), N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA). The measurements have been made at 298.15K and mole fraction of amide x2=(0–0.4) on the precise isothermic calorimeter. The results obtained have been used to calculate the standard enthalpies of solution (ΔsolH°) and transfer (ΔtrH°) of L-phenylalanine from water into mixtures as well as the enthalpy coefficients of pairwise interaction (hxy) of the solute with amide in aqueous media. The interrelation between enthalpy characteristics of dissolution (transfer) of L-phenylalanine and the composition of (water+amide) binary mixtures has been established. Contributions of the amides properties (molar volume, dipolarity/polarizability, acidity and basicity) to the energy of pairwise interactions have been estimated quantitatively by means of a modified Kamlet–Taft equation.

Chiral polyaniline with flaky, spherical and urchin-like morphologies synthesized in the l-phenylalanine saturated solutions

Chiral polyaniline (PANI), of flaky, spherical and urchin-like morphologies, was synthesized in the saturated l-phenylalanine solution by adjusting the molar ratio of l-phenylalanine to aniline from 0.25 to 40. The concentration of l-phenylalanine solution was constant, which was different from the conventional synthesis. The morphologies of PANI were observed by scanning electron microscopy. The molar ratio of l-phenylalanine to aniline and the amount of aniline were proposed to be crucial to the morphologies. Circular dichroism spectra confirmed that l-phenylalanine endowed predominately one type of chirality to polyaniline by hydrogen bonding. The optical, structural and electrochemical properties of these synthesized PANI were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry, respectively. There were some insulating structures, such as oligomers, in the PANI chains, which were caused by the weak acid circumstance during the polymerization.

The thermodynamic parameters of the step dissociation of L-phenylalanyl in aqueous solution

The heats of interaction of L-phenylalanine with solutions of nitric acid and potassium and lithium hydroxides were determined calorimetrically at 288.15, 298.15, and 308.15 K and solution ionic strengths of 0.5, 0.75, and 1.0 in the presence of LiNO3 and KNO3. The standard thermodynamic characteristics (Δr H°, Δr G°, Δr S°, and ΔC p ° of acid-base interactions in aqueous solutions of L-phenylalanine were calculated. The influence of the concentration of background electrolytes and temperature on the heats of dissociation of L-phenylalanine was considered. A comparative analysis of the standard thermodynamic characteristics of step dissociation of L-phenylalanine and alanine was performed in terms of the modern concepts of the structure and physicochemical properties of these compounds and their solutions.

The aromatic amino acid behaviour in aqueous amide solutions

The enthalpies of solution of L-phenylalanine in the mixtures of water with the protein denaturant urea have been measured in the temperature range of 288.15–318.15 K. Using the results of the present research and literature data of free energies, the standard thermodynamic functions of the solute transfer from water to aqueous urea solutions have been estimated in a wide temperature range. The enthalpic, heat capacity, entropic and free energy parameters of the solute-urea pair and triplet interactions have been computed. The amino acid — amide pair interaction was found to be attractive in the temperature range studied due to the favourable enthalpic term. The triplet interaction being slightly repulsive reveals the enthalpic origin also. The examination of the Savage and Wood additivity-of-groups approach does indicate the inapplicability of this scheme to enthalpies and entropies of interaction. It has been found for the first time that the heat capacity of interaction changes its sign at 303 K, i.e. the temperature dependence of enthalpic and entropic parameters passes through the pronounced extrema near the temperature of the minimum of the heat capacity of pure water.

Thermodynamics of interaction of L-α-phenylalanine with urea and dimethylformamide in aqueous solution

The thermal effects of solution of L-phenylalanine in aqueous solutions of urea and dimethylformamide (DMF) at 25°C were determined. The solubility of L-phenylalanine in water and aqueous DMF solutions was measured. The standard enthalpies, free energies, and entropies of solution of the amino acid in aqueous solutions of amides were calculated. The parameters of pair and ternary amino acid-amide interactions were determined within the framework of the McMillan-Mayer theory. The amino acid-amide pair interaction is accompanied by a decrease in the Gibbs free energy, controlled by the entropy term with DMF and by the enthalpy term with urea. The interaction of L-phenylalanine with two amide molecules is repulsive, which in the case of DMF leads to an increase in the standard free energies of solution of the amino acid at the amide mole fraction X 2 > 0.05.

The thermodynamic parameters of solution of L-phenylalanine in water

The heat effects of solution of L-phenylalanine in water were measured over wide concentration and temperature ranges. The enthalpies of solution of L-phenylalanine were found to be independent of the content of the amino acid in solution over the concentration range studied. The standard enthalpies, heat capacities, and entropies of solution of the amino acid and the solubility of L-phenylalanine over the temperature range studied were calculated.

Role of Glutamine Depletion in Directing Tissue-specific Nutrient Stress Responses to L-Asparaginase

Role of Glutamine Depletion in Directing Tissue-specific Nutrient Stress Responses to L-Asparaginase

THE IMMOBILIZATION OF AMINOACYLASE AND THE RESOLUTION OF D,L-PHENYLALANINE

A polymer with suitable physical characters and matched functional groups was synthesized,and used as a supporter to immobilize aminoacylase. The results showed that this supporterhad high immobilizing capacity and high selectivity for aminoacylase. Immobilized amino-acylase had high specific activity. In this paper, we determine the physical and chemicalcharacters of aminoacylase for resolution of D,L--phenylalanine, including its optimum tem-perature, pH, ion concentration, activated ion, substrate concentration, thermal stability anddenaturation. The immobilized aminoacylase was used to resolve the D,L-phenylalaninecontinuously. Thc resolved products was separated and purified with ion-exchange resins. L-phenylalanine solution was concentrated by vacuum evaporation and its hydrochloride wasformed. Checking of final product with polarimeter showed high yield and purity.

Monitoring of phenylketonuria: A colorimetric method for the determination of plasma phenylalanine using l-phenylalanine dehydrogenase

A simple, rapid, accurate, and precise colorimetric assay for the determination of l-phenylalanine in plasma samples using l-phenylalanine dehydrogenase [ l-phenylalanine:NAD +-oxidoreductase (deaminating)] from Rhodococcus sp. M 4 is described. The enzyme catalyzes the NAD-dependent oxidative deamination of l-phenylalanine. However, the equilibrium of reaction favors l-phenylalanine formation. By stoichiometric coupling of this reaction with diaphorase/iodonitro tetrazolium chloride (INT) the formed NADH converts INT to a formazan whereby the reaction is displaced in favor of phenylpyruvate. Using a kinetic approach the increase in absorbance at 492 nm shows linearity over more than 30 min. Deproteinized standard solutions of l-phenylalanine in the range from 30 to 1200 μmol/liter show a linearity between the dA formazan/30 min and the substrate concentration. In phenylketonuria (PKU) plasma samples no interferences caused by l-tyrosine or phenylpyruvic acid are seen. Applicability is demonstrated by comparative determination of plasma l-phenylalanine of treated PKU patients by the colorimetric method and automated amino acid analysis.

Enzymatic determination of l-phenylalanine and phenylpyruvate with l-phenylalanine dehydrogenase

An enzymatic method is described for the determination of l-phenylalanine or phenylpyruvate using l-phenylalanine dehydrogenase. The enzyme catalyzes the NAD-dependent oxidative deamination of l-phenylalanine or the reductive amination of the 2-oxoacid, respectively. The stoichiometric coupling of the coenzyme allows a direct spectrophotometric assay of the substrate concentration. The equilibrium of the reaction favors l-phenylalanine formation; however, by measuring initial reaction velocities, the enzyme can be used for l-phenylalanine determination, too. Standard solutions of l-phenylalanine in the range of 10–300 μ m and of phenylpyruvate (5–100 μ m) show a linearity between the value for dE NADH/min and the substrate concentration. Besides phenylalanine, the enzyme can convert tyrosine and methionine, and their oxoacids, respectively. The K m values of these substrates are higher. The influence of tyrosine on the determination of phenylalanine was studied and appeared tolerable for certain applications.

"Fragmented" isoenzymes of alkaline phosphatase in the diagnosis of transient hyperphosphatasemia.

We describe the appearance of "fragmented" isoenzymes of serum alkaline phosphatase (EC 3.1.3.1) in two cases of transient hyperphosphatasemia. We determined the isoenzymes by liquid chromatography, then characterized them by heat inactivation, inhibition with 5 mmol/L L-phenylalanine solution, and electrophoresis on cellulose acetate membranes. We suspect that a virus-induced decrease in clearance of the enzyme from serum is responsible for a similar increase of bone and liver isoenzyme activities and for the presence of these fragmented isoenzymes in transient hyperphosphatasemia.