Amino Acids In Aqueous Solutions Research Articles

Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Complex formation of aqua palladium(II) ions with glycine (Gly), β‑alanine (β-Ala), and taurine (Tau) in aqueous solution was studied by spectrophotometric titration at I = 1.0 mol/L (HClO4 + NaClO4) and T = 25 ± 1°C. A monoligand complex appeared at pH 0 in the H‒Pd–Gly system under the conditions of our experiment; mono- and biscomplexes were formed at pH 1. In the H‒Pd‒β-Ala system, a monoligand complex was formed at pH 1 and mono- and biscomplexes were formed at pH 2. In the H‒Pd‒Tau system, a monoligand complex was formed at pH 1 and 2. Molar absorption coefficients were calculated: the peak absorption occurs at λ = 370 nm and ε = 203 L/(mol cm) for the monoligand glycinate complex [PdGly(H2O)2]+; at λ = 325 nm and ε = 274 L/(mol cm) for the biscomplex [PdGly2]0; at λ = 365 nm and ε = 342 and 297 L/(mol cm) for the β‑alaninate [Pdβ‑Ala(H2O)2]+ and taurinate [PdTau(H2O)2]+ monoligand complexes, respectively; and at λ = 330 nm and ε = 549 L/(mol cm) for the β‑alaninate biscomplex [Pdβ‑Ala2]0. Logarithmic concentration formation constants were calculated for glycinate (log β1 = 15.03 ± 0.07, and log β2 = 28.97 ± 0.28), β-alaninate (log β1 = 13.94 ± 0.05, and log β2 = 25.24 ± 0.06), and taurinate (log β1 = 9.74 ± 0.08) palladium(II) complexes.

Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Determination of osmotic coefficients and activity coefficients of calcium d-pantothenate, cefazolin sodium, and ceftriaxone sodium drugs in aqueous solutions of amino acids by using vapor pressure osmometry at 310.15 K

Fundamental and serious efforts have been made over the past years to improve the drug acts, which leads to the discovery of novel drug preparations and delivery systems. The optimal design of such processes requires a molecular-level understanding of the interactions between drug molecules and biomolecules such as proteins. The thermodynamic investigation provides deep insight and knowledge of solute-solvent interactions and selection of appropriate production compounds in pharmaceutical fields. Particularly, the study of drug + biomolecule in aqueous media is the central issue in many types of research. The osmotic coefficient data for aqueous solutions containing the drugs (calcium d-pantothenate (CDP), cefazolin sodium (CFZ.Na), ceftriaxone sodium (CFT.Na)) with simple amino acid, l-alanine, glycine and l-leucine are obtained at 310.15 K using vapor pressure osmometry. Activity coefficients of both components in mixture were estimated using experimental osmotic coefficients. According to the results, the values of osmotic coefficients for the ternary system (drug + water + l-leucine) with a concentration of 0.04 mol∙kg−1 are higher than those values in other systems. The concentration dependence of osmotic coefficients indicates ion-pair formation between the ions of the drugs. Finally, Lin et al. and ECA models were used to correlate the water activity data in the presence of the amino acids obtained for the aqueous solution (drug + water + amino acid).

Impact of an Ionic Liquid on Amino Acid Side Chains: A Perspective from Molecular Simulation Studies.

Ionic liquids (ILs) are known to modify the structural stability of proteins. The modification of the protein conformation is associated with the accumulation of ILs around the amino acid (AA) side chains and the nature of interactions between them. To understand the microscopic picture of the structural arrangements of ILs around the AA side chains, room temperature molecular dynamics (MD) simulations have been carried out in this work with a series of hydrophobic, polar and charged AAs in aqueous solutions containing the IL 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) at 2 M concentration. The calculations revealed distinctly nonuniform distribution of the IL components around different AAs. In particular, it is demonstrated that the BMIM+ cations preferentially interact with the aromatic AAs through favorable stacking interactions between the cation imidazolium head groups and the aromatic AA side chains. This results in preferential parallel alignments and enhanced population of the cations around the aromatic AAs. The potential of mean force (PMF) calculations revealed that such favorable stacking interactions provide greater stability to the contact pairs (CPs) formed between the aromatic AAs and the IL cations as compared to the other AAs. It is further quantified that for most of the AAs (except the cationic ones), a favorable enthalpy contribution more than compensates for the entropy cost to form stable CPs with the IL cations. These findings are likely to provide valuable fundamental information toward understanding the effects of ILs on protein conformational stability.

Study of Thermodynamic Properties of l-Serine and l-Threonine in Aqueous Solutions of 1-(2-Carboxyethyl)-3-methylimidazolium Chloride [HOOCEMIM][Cl

The stability of amino acids in solutions containing electrolytes and the effect of ambient pH on their biological activity is an important research area. In this research work, the volumetric and transport properties of ionic liquid (IL) aqueous solution with special performance of 1-(2-carboxyethyl)-3-methylimidazolium chloride ([HOOCEMIM][Cl]) were studied. The selected IL acts as an electrolyte and allows the study of systems containing amino acids at acidic pH. In this work, the density, speed of sound and viscosity of binary and ternary solutions of IL in aqueous solution of amino acids in the structure of proteins, namely l-serine and l-threonine within IL molality range of (0.05, 0.07 and 0.09 mol·kg−1) were measured at 298.15 K. From these quantities, apparent molar volume, limiting apparent molar volume, apparent molar isentropic compression, limiting apparent molar isentropic compression, transfer standard volumes for amino acids from water to the aqueous IL solutions and viscosity B-coefficients were calculated using the equations of Redlich–Meyer and Jones–Dole. Close examination of literature indicates that there is no data for water activity for solution of l-serine + H2O at 308.15 and 318.15 K. In this way water activity, osmotic coefficient and vapor pressure were measured and using the interaction parameters of Wilson, NRTL, NRF-NRTL and UNIQUAC models, activity coefficient values of l-serine calculated.

Development of Thermophysical Property Models for Aqueous Amino Acid Solutions

AbstractModels for the calculation of density, heat capacity, viscosity, and thermal conductivity of amino acid aqueous solutions were proposed. Density, heat capacity, viscosity, and thermal conductivity of pure amino acid liquids were predicted by the Rackett model, Watson model, Heu‐Sheu‐Tu group contribution method, and Sato‐Riedel model, respectively. Mixing rule equations required for the prediction of density, heat capacity, viscosity, and thermal conductivity of amino acid aqueous solutions were suggested. Density, heat capacity, viscosity, and thermal conductivity data of 930, 975, 450, and 167 data points, respectively, for 20 amino acid aqueous solution systems were regressed to determine the most appropriate mixing rule parameters.

Evidence of excited-state lifetime enhancement in dimyristoyl-phosphocholine nanodiscs by ultraviolet absorption spectroscopy

Ultraviolet absorption spectroscopy is an analytical tool that is commonly utilized to determine protein concentrations, primarily due to characteristic absorption of tryptophan and tyrosine at 280 nm. Accurate concentration determination is essential to the accuracy of many biophysical techniques, and ultraviolet absorption provides a convenient and rapid method to assess protein concentration. However, the widespread usage of this method assumes that ultraviolet absorption is the same for individual amino acids in aqueous solution (where the molar extinction coefficient was measured) as for the amino acid in the conformational environment of the protein of interest. We demonstrate that additional considerations may be necessary for the membrane scaffold protein in dimyristoyl-phosphocholine nanodiscs through ultraviolet absorption spectroscopy of nanodiscs, liposomes, the membrane scaffold protein, and a mixture of liposomes and the non-nanodisc-associated protein. The aromatic amino acids of the membrane scaffold protein absorb significantly less light at 280 nm when associated with lipids in a lipoprotein assembly, which we plausibly attribute to an enhancement of chromophore excited-state lifetimes due to reduced intramolecular motion in the nanodisc. We caution that using the molar absorptivity of the membrane scaffold protein alone to determine nanodisc concentrations may not yield accurate results. Instead, the molar absorptivity of each nanodisc formulation should be explored independently to account for the unique conformational environment of each nanodisc.

Volumetric Properties of Aqueous Sodium Salt of Amino Acids as CO2 Capture Solvent

Objectives: To produce new and accurate data of density of aqueous solution of amino acid salts at different temperatures and to correlate it with molality. Methods: The densities of aqueous solutions of sodium salts of Amino acids such as L-cysteine, L-leucine, L-proline and L-valine have been measured using double-arm Pycnometer, placed in a transparent glass-walled water bath having thermal stability of (0.01 K) at concentrations range (0.01 to 0.15) mol L-1 and at 298.15, 303.15, 308.15, and 313.15 K. From density data ahead, apparent molar volumes (Vϕ ), the partial molar volumes (Vϕ 0), expansion coefficient (E¥) and Hepler’s constant ( ¶ 2Vϕ 0=¶ T2) were calculated and analysed on the basis of the intermolecular interaction and molecular structure. Findings: The densities are observed to increase with concentration and decrease with increasing temperature. The positive values of partial molar volume (Vϕ 0) indicate strong sodium amino acids -water interactions. Novelty: For studied aqueous sodium salt solution of Amino acids, such properties have not yet been reported in the open literature and at such a lower concentrations range (0.01 to 0.15) mol L-1. Keywords: Density; Sodium Salt Amino Acid; Apparent Molar Volume; Helper’s Constant

Thermodynamic study of calcium d-pantothenate drug in the presence of aqueous solutions including some amino acids: Volumetric and compressibility properties

The impressive and remarkable efforts have been made over the past years to improve the production, formulation and purification of active ingredients pharmaceutical which leads to the discovery of novel drug preparations and delivery systems. The optimal design of such processes requires a molecular-level understanding of the interactions between drug molecules and biological membranes. The thermodynamic investigation provides deep and complete knowledge of interactions and the choice of appropriate and suitable compounds in pharmaceutical fields. Particularly, the analysis of drugs + biomolecules in aqueous solutions is the central issue in many types of research because they exert their impact by interacting with biological membranes. This work is aimed to measure the density and speed of sound for the calcium d-pantothenate, vitamin B5 calcium salt (CDP) in aqueous solutions of amino acids (glycine, l-alanine, and l-leucine) at temperature ranges (293.15 to 308.15) K. By correlating of the measured physical quantities in with standard relations, apparent molar volumes, Vϕ,m, and apparent molar isentropic compression, κs,ϕ,m, are calculated. In addition, apparent molar isobaric expansion, Eϕ,m0, and Hepler’s constant are computed. For fitting the experimental Vϕ,m and κϕ the Redlich-Meyer equation was employed that the important quantities; standard partial molar volume, Vϕ0 , and partial molar isentropic compression, κϕ0, were obtained.

Microwave characterization of aqueous amino acid solutions using the multifrequency WGM resonator technique.

Amino acids play essential role for humans. We studied the dielectric properties of the basic aliphatic amino acids and polar positive amino acids in solutions of different concentrations. The high-Q single microwave whispering gallery-mode (WGM) quartz dielectric resonator based technique, enhanced to a number of measurement frequencies, was applied. The technique allows liquid investigation of micro- to nano- liter volumes filled in microfluidic channel on six discrete frequencies in the 30-40GHz range. The dependencies of the complex permittivity on the molar mass show almost linear behavior for aliphatic amino acids at different concentrations. The study results are in good agreement with the calculated data obtained by Cole-Cole equation.

Investigating the kinetics of CO2 absorption in aqueous sodium serinate/piperazine solutions: An experimental and mathematical modeling

Aqueous solutions of amino acids are some of the most important alternatives to conventional alkanolamines for gas absorption applications. This study investigates the kinetics of CO2 absorption in sodium serinate solutions and their blend with piperazine. To that end, the kinetic analysis for sodium serinate was performed at 0.5, 1, 2, and 4 kmol/m3 concentration levels. The blended solution was prepared with 1 kmol/m3 of sodium serinate solution as the main component and piperazine in 0.5, 1, and 2 kmol/m3 concentration levels as the additive. The temperature ranged from 293 to 323 K. The density and viscosity of the solutions, gas solubility in the liquid, and physical mass transfer coefficient of the liquid phase were measured directly. The gas diffusion coefficient in the solution was calculated using the modified Stokes-Einstein relation. At constant concentration, the CO2 absorption rate increased by increasing temperature, while at a constant temperature, the rate directly correlated with concentration up to an optimum level. Beyond the optimum concentration, an increase in concentration decreased the rate. Here, a rate equation for the absorption of CO2 in sodium serinate/piperazine solutions was developed. It can be concluded that aqueous solution of sodium serinate can be used as a CO2 absorbent. Moreover, adding piperazine to the aqueous solution of sodium serinate can improve the CO2 absorption efficiency.

Study on vapor-liquid equilibrium and microscopic properties of DL-proline, L-glutamic acid, and L-serine aqueous solutions.

The vapor–liquid equilibrium (VLE) in aqueous amino acid solutions is essential in chemical production, such as purification, isolation, or crystallization of amino acid intermediates. In this work, VLE of DL-proline, L-glutamic acid, and L-serine aqueous solutions was measured at pressures ranging from 4.82 to 102.58 kPa. The developed model was successfully applied to correlate experimental data with temperatures in the range of 298.15–382.75 K. Model parameters (h, , , , and ) were given. Moreover, the amino acid aqueous solution was investigated by Fourier transform infrared spectroscopy (FTIR). By analyzing infrared spectra, the strength of intermolecular interactions was obtained, and the structure–activity relationship between the microscopic interactions and the VLE was established.

Vitamin C-amino acid interactions in aqueous solutions: Volumetric and interfacial properties

Nature of interactions occurring in aqueous solutions have been studied to understand various phenomena such as protein stabilization, drug-delivery, and food preservation. These interactions have been studied by measuring physicochemical properties of mixed aqueous solutions. Herein, we have measured the volumetric and interfacial properties of vitamin C (VC) in aqueous solutions of amino acids (Glycine, Gly; L-Leucine, Leu). Volumetric were studied at temperatures (298.15 K to 313.15 K). Transfer volumes were obtained from infinite dilution partial molar volumes of VC in aqueous Gly-and Leu-solutions. Positive transfer volumes (∆tV2° and ∆tK2) were observed, which decreases as Gly > Leu, suggesting dominance of hydrophilic-ionic interactions. Double derivative, (∂2V2° /∂T2)P suggest chaotropic nature of VC in presence of amino acids. Nature of interactions influencing interfacial properties (contact angle and surface tension) has also been evaluated at 298.15 K. Solute-co-solute interactions not much influence the interfacial properties.

The Artificial Synthesis of Raphide

Have you ever had an itchy mouth after eating yam? This is because the calcium oxalate needle shaped crystals, known as raphide, is contained in the plant that irritate the skin. raphide has been studied in various fields such as medicine and agriculture because of their characteristic effects. Although previous studies have reported useful effects, no successful artificial synthesis of raphide crystals has yet been reported. Therefore, I researched for factors that affect the synthesis of raphide. First, I conducted targeted experiments on drop rate, rotation speed, and concentration. As a result, it was found that the drop rate and rotation speed are factors that change the crystal structure. When these crystals were analyzed by X-ray crystallography, it was confirmed that they were calcium oxalate crystals. However, they were not raphide, so I attempted to synthesize them using a catalyst. For the catalyst, I decided to use the cell fluid part of aloe vera and an aqueous solution of amino acids. When the synthesized crystals were observed under a microscope, there were few raphide could be seen. Furthermore, since the extracted crystals may be the catalytic amino acid, ninhydrin reaction was performed on the filtrate and crystals, and no reaction was observed in both. Since it reacted in the solution before the experiment, I can say that it is calcium oxalate crystal. Therefore, it can be said that the synthesis of raphide was successful and the purpose of the research was achieved.

Solvation Properties of Branched-Chain Amino Acids in Aqueous Solutions of 1-Dodecyl-3-methylimidazolium Bromide at Different Temperatures: Volumetric and Acoustic Measurements

Solvation Properties of Branched-Chain Amino Acids in Aqueous Solutions of 1-Dodecyl-3-methylimidazolium Bromide at Different Temperatures: Volumetric and Acoustic Measurements

MAIN TRENDS AND DIFFERENCES IN THE COMPLEX FORMATION OF AMINO ACIDS WITH CALCIUM(II) AND MAGNESIUM(II) IONS ACCORDING TO OPTICAL SPECTROSCOPY DATA

The thermodynamic stability constants of coordination compounds of calcium(II) and magnesium(II) ions with amino acids in aqueous solutions at 298 K were calculated by spectrophotometry using the mathematical processing of experimental data. The main principles and approaches of mathematical processing are shown. Differences of calcium(II) and magnesium(II) ions as complexing amino acids as ligands are indicated, a regularity in the complex formation of amino acids of various structures is established.

Simultaneous Discrimination and Quantification of Enantiomeric Amino Acids under Physiological Conditions by Chiral 19F NMR Tag.

Enantiomeric analysis is of great significance in chemistry, chemical biology and pharmaceutical research. We herein propose a chiral 19F NMR tag containing an amino reactive NHS group to discriminate the enantiomeric amino acids under physiological conditions by NMR spectroscopy. The chiral 19F NMR tag readily forms stable amide products with the amino acids in aqueous solution. The stereospecific chemistry of enantiomeric amino acids is discriminated by a stereogenic carbon bonded with a 19F atom and is therefore decoded by the 19F reporter and manifested in the distinct 19F chemical shift. The chemical shift difference (ΔΔδ) of the chiral 19F NMR tag derived enantiomeric amino acids variants has a broad chemical shift range between -1.13 to 1.68 ppm, indicating the high sensitivity of the chiral 19F NMR tag to the stereospecific environment surrounding the individual amino acids. The distinguishable chemical shift produced by the chiral 19F NMR tag permits simultaneous discrimination and quantification of the enantiomeric amino acids in a mixture. The high fidelity of the chiral 19F NMR tag affords high-accuracy determination of the enantiomeric composition of amino acids by simple 1D NMR under physiological conditions.

Reversible and Efficient Absorption of SO2 with Natural Amino Acid Aqueous Solutions: Performance and Mechanism

Reversible and Efficient Absorption of SO₂ with Natural Amino Acid Aqueous Solutions: Performance and Mechanism

Molecular dynamics calculations of partial molar volumes of amino acids in aqueous solutions

Partial molar volumes of amino acids in their zwitterionic and molecular forms were calculated using molecular dynamics simulations of these systems in aqueous solutions. Calculations performed with the TIP4P, SPC (rigid and flexible), SPC/E, and polarizable water models showed that the choice of water model can have a significant impact on the calculated volumes. The effect of treatment of long-range electrostatic interactions on the calculated results was also investigated. The volumes obtained in simulations with a properly chosen water model fit well the experimental data for both molecular and zwitterionic forms of amino acids.

Efficient Oligomerization of Aromatic Amino Acids Induced by Gaps in Four-Helix Bundles of DNA or RNA.

The formation of peptides from amino acids is one of the processes associated with life. Because of the dominant role of translation in extant biology, peptide‐forming processes that are RNA induced are of particular interest. We have previously reported the formation of phosphoramidate‐linked peptido RNAs as the products of spontaneous condensation reactions between ribonucleotides and free amino acids in aqueous solution. We now asked whether four‐helix bundle (4HB) DNA or RNA folding motifs with a single‐ or double‐nucleotide gap next to a 5’‐phosphate can act as reaction sites for phosphoramidate formation. For glycine, this was found to be the case, whereas phenylalanine and tryptophan showed accelerated formation of peptides without a covalent link to the nucleic acid. Free peptides with up to 11 tryptophan or phenylalanine residues were found in precipitates forming in the presence of gap‐containing DNA or RNA 4HBs. Control experiments using motifs with just a nick or primer alone did not have the same effect. Because folded structures with a gap in a double helix are likely products of hybridization of strands formed in statistically controlled oligomerization reactions, our results are interesting in the context of prebiotic scenarios. Independent of a putative role in evolution, our findings suggest that for some aromatic amino acids an RNA‐induced pathway for oligomerization exists that does not have a discernable link to translation.