Aqueous Solutions Of L-alanine Research Articles

Thermodynamic Characteristics of the Formation of Iron(II) and Iron(III) Complexes with L-Alanine in Aqueous Solutions

Thermodynamic Characteristics of the Formation of Iron(II) and Iron(III) Complexes with L-Alanine in Aqueous Solutions

Molecular Interaction Studies of Doxycycline Hyclate in Aqueous Glycine or l-Alanine by Using Volumetric and Ultrasonic Parameters

The intermolecular interactions of the antibiotic drug doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine were determined by using volumetric and acoustic methods at four different temperatures (305.15, 310.15, 315.15 and 320.15) K. The limiting partial molar volume $$(V_{\phi }^{{\text{o}}} )$$ , limiting standard partial molar volume of transfer $${(}\Delta_{{{\text{tr}}}} V_{\phi }^{{\text{o}}} )$$ , limiting partial molar adiabatic compressibility ( $$\kappa_{\phi ,s}^{{\text{o}}} )$$ and limiting partial molar adiabatic compressibility of transfer $${(}\Delta_{{{\text{tr}}}} \kappa_{\phi ,s}^{{\text{o}}} )$$ were calculated from the density and ultrasonic velocity data at different temperatures and the results suggest strong solute–solvent interactions. The caging effect of doxycycline hyclate in water and in aqueous solutions of glycine and aqueous solutions of l-alanine was studied using the positive values of $$\left( {E_{\phi }^{{\text{o}}} = \frac{{{\updelta }V_{\phi }^{{\text{o}}} }}{{{\updelta }T}}} \right)$$ . The structure making behavior of doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine was analyzed from the positive values of Hepler’s constant i.e. $$\left( {\frac{{{\updelta }^{2} V_{\phi }^{{\text{o}}} }}{{{\updelta }T^{2} }}} \right)$$ . The limiting isobaric thermal expansion coefficient $$\left( {\alpha^{{\text{o}}} { } = \frac{{E_{\phi }^{{\text{o}}} }}{{V_{\phi }^{{\text{o}}} }}} \right)$$ , intermolecular free length (Lf) and acoustic impedance (Z) of doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine were also calculated at the studied temperatures.

Molecular Interactions of Non-Steroid Anti-Inflammatory Drug Dolonex in Aqueous Solutions of L-Alanine/L-Valine at Different Temperatures: Viscometric Approach

The viscosities of aqueous solutions of L-alanine and L-valine with non-steroid anti-inflammatory drug dolonex (0.020, 0.040, 0.060 mol kg–1) have been measured at different temperatures (293.15–313.15 K) and at atmospheric pressure. On the basis of experimental results Jones–Dole coefficient-B, viscosity B-coefficient of transfer, activation parameters i.e., free energy of activation of viscous flow per mole of solvent $$\Delta \mu _{2}^{{^\circ \# }}$$ and per mole of solute $$\Delta \mu _{1}^{{^\circ \# }}$$ were determined. The obtained results were discussed in terms of solute–solvent interactions in these solutions. Moreover, structure breaker tendency of solute molecules were obtained by measuring temperature derivative of viscosity B-coefficient.

Thermodynamic Study of L-alanine in Aqueous Solutions of 1-Hexyl-3-Methylimidazolium Ibuprofenate as an Active Pharmaceutical Ingredient Ionic Liquid (API-IL)

The present work reported density, viscosity, speed of sound, electrical conductivity and refractive index data of L-alanine in the aqueous solutions of 1-hexyl-3-methylimidazolium ibuprofenate at T= 298.15 K. Using the measured data, partial molar volume of transfer ( ), partial molar isentropic compressibility of transfer ( ), viscosity B-coefficient of transfer (∆traB), ion association constant (KA) and molar refraction (RD) quantities were calculated. The obtained parameters provide the information about the solvation properties of aqueous solutions of L-alanine in the presence of [HMIm][Ibu]. The positive values of , and ∆traB are indicative of the ion-polar and polar-polar interactions between [HMIm][Ibu] and L-alanine. In addition, decreeing the KA values with addition of L-alanine to the [HMIm][Ibu] solutions suggests that the ion pair formation don’t proceed spontaneously at higher concentration of amino acid.

Effect of Amino Acids and Sodium Chloride on d-Sorbitol in Aqueous Solutions at Different Temperatures: Volumetric and Acoustic Approach

Apparent molar volumes and apparent molar compressibilities for d-sorbitol in (0.05, 0.1, 0.2 and 0.3) mol·kg−1 aqueous solutions of l-alanine, l-cysteine and l-histidine and NaCl have been determined from measurements of solution density at T = (288.15, 298.15, 308.15 and 318.15) K and sound velocity at T = 298.15 K, as a function of the concentration of the sugar alcohol. The data were used to obtain the limiting apparent molar volumes, limiting apparent molar compressibilities and the corresponding transfer parameters. Limiting apparent molar expansibilities and their second order derivatives and volume interaction coefficients were also estimated. These parameters are discussed in terms of d-sorbitol and co-solute (amino acid or sodium chloride) interactions in aqueous solutions.

Investigation of Volumetric and Acoustic Properties of Procainamide Hydrochloride in Aqueous Binary and (Water + Amino Acid) Ternary Mixtures at Different Temperatures

For effective drug design and development, an integrated process utilizing all available information from structural, thermodynamic, and biological studies plays a very important role. To understand the energy basis of molecular interactions utilizing various thermodynamic methods, volumetric and acoustic studies are vital early in the development process of any drug toward an optimal energy interaction profile while retaining a good pharmacological assay. In this article, we are reporting the data of densities (ρ) and speeds of sound (u) of an antiarrhythmic agent, namely, procainamide hydrochloride in an aqueous binary and aqueous solution of amino acids, i.e., l-alanine and l-valine at T = (298.15, 308.15 and 318.15) K. Different thermodynamic parameters such as the apparent molar volume (Vϕ) of the solute, the isentropic compressibility (κs) of the solution, and the apparent molar isentropic compressibility (κϕ) of procainamide hydrochloride in water and aqueous solutions of l-alanine and l-valine have been computed using the density and speed of sound data at different temperatures. The limiting apparent molar volume (Vϕ0) of solute and the limiting apparent molar compressibility (κϕ0) of solute in binary and ternary aqueous solutions have been obtained by extrapolating the plots. The results have been interpreted in light of the competing solute–solute and solute–solvent interactions.

Effect of 1-Butyl-3-methylimidazolium Ibuprofenate as an Active Pharmaceutical Ingredient Ionic Liquid (API-IL) on the Thermodynamic Properties of Glycine and l-Alanine in Aqueous Solutions at Different Temperatures

Recently, ionic liquids have been combined with active pharmaceutical ingredients (APIs), and a third generation of ILs has emerged (API-ILs). The effect of a novel ionic liquid containing the ibuprofenate anion as an active pharmaceutical ingredient ionic liquid (API-IL) on the thermodynamic properties of two amino acids, glycine and l-alanine, have been studied. The densities, speeds of sound, viscosities and refractive indices of glycine and l-alanine in water and in aqueous solutions of an API-IL, 1-butyl-3-methylimidazolium ibuprofenate ([BMIM][Ibu]), have been determined at temperatures 288.15–318.15 K. The measured data have been used to calculate the standard partial molar volume $$ V_{\phi }^{0} $$ , partial molar volume of transfer $$ \Delta_{\text{tr}} V_{\phi }^{0} $$ , Hepler’s constant $$ (\partial^{2} V_{\phi }^{0} /\partial T^{2} )_{p} $$ , apparent molar isentropic compressibility $$ \kappa_{\phi } $$ , molar refraction R D, viscosity B coefficient (B) and hydration number parameters n H. All of these parameters are discussed in terms of the competitive interactions occurring between amino acids–[BMIM][Ibu] and amino acids–water.

Formation of 4(5)-Methylimidazole in Aqueous d-Glucose-Amino Acids Model System.

The International Agency for Research on Cancer (IRAC) has classified 4(5)-methylimidazole (4-MeI) as a group 2B possible human carcinogen. Thus, how 4-MeI forms in a D-glucose (Glu) amino acids (AA) model system is important, as it is how browning is affected. An aqueous solution of Glu was mixed individually in equimolar amounts at 3 concentrations (0.05, 0.1, and 0.15 M) with aqueous solutions of L-Alanine (Ala), L-Arginine (Arg), Glycine (Gly), L-Lysine (Lys), and L-Serine (Ser). The Glu-AA mixtures were reacted at 60, 120, and 160 °C for 1 h. The 4-MeI levels were measured by gas chromatography-mass spectrometry after derivatization with isobutylchloroformate. No 4-MeI was formed at 60 °C for any treatment combination; however, at 120 °C and 0.05 M, Glu-Arg and Glu-Lys produced 0.13 and 0.14 mg/kg of 4-MeI. At 160 °C and 0.05 M all treatment combinations formed 4-MeI. At 160 °C and 0.15 M, the observed levels of Glu-Ala, Glu-Arg, Glu-Gly, Glu-Lys, and Glu-Ser were 0.21, 1.00, 0.15, 0.22, and 0.16 mg/kg. The AA type, reactant concentrations, and temperature significantly affected (P < 0.001) formation of 4-MeI as well as browning. Glu-Lys treatment in all combinations produced the most browning, but Glu-Arg produced the most 4-MeI. This method showed that foods processed using low temperatures may have reduced levels of 4-MeI.

Molecular-structure variation of biomolecules irradiated with atmospheric-pressure plasma through plasma/liquid interface

Plasma interactions with organic materials through a plasma/liquid interface have been investigated via the degradation of l-alanine in liquid by irradiation with atmospheric-pressure He plasma. The optical emission spectra of atmospheric-pressure He plasma show considerable emissions of He lines and emissions of O, N, H, and OH radicals attributed to the dissociation of air and water. Variation in the molecular structure of l-alanine in aqueous solution irradiated with the plasma has been observed by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoemission spectroscopy (XPS). The results obtained from FT-IR and XPS analyses show that the atmospheric-pressure He plasma exposure affects the structural variation of l-alanine in solution owing to the oxidation by irradiated radicals from plasma through the plasma/liquid interface.

Growth and characterization of pure and semiorganic nonlinear optical Lithium Sulphate admixtured l-alanine crystal

Lithium sulphate admixtured l-alanine (LSLA) salt was synthesized and the solubility of the commercially available l-alanine and the synthesized LSLA sample was determined in de-ionized water at various temperatures. In accordance with the solubility data, the saturated aqueous solutions of l-alanine and lithium admixtured l-alanine were prepared separately and the single crystals of the samples were grown by the solution method with a slow evaporation technique. Studying single x-ray diffraction shows that pure and LSLA crystal belong to the orthorhombic system with a non-centrosymmetric space group P212121. Using the powder x-ray diffraction study, the crystallinity of the grown crystals is confirmed and the diffraction peaks are indexed. The various functional groups present in the pure and LSLA crystal are elucidated from Fourier transform infrared spectroscopy study. UV–visible transmittance is recorded to study the optical transmittance range for the grown crystals. The powder second harmonic generation test confirms the nonlinear optical property of the grown crystals. From the microhardness test, the hardness of the grown crystals is estimated. The dielectric behaviour, such as the dielectric constant and the loss of the sample, are measured as a function of temperature and frequency. The ac conductivity of the grown crystals is also studied and the activation energy is calculated.

Plasma Interactions with Biological Molecules in Aqueous Solution

ABSTRACTPlasma interactions with L-alanine in aqueous solution have been examined as a basis of fundamental processes in plasma medicine. The plasma interactions with L-alanine in aqueous solution have been examined for investigations of chemical modifications induced by exposures with the atmospheric-pressure hollow-cathode He plasma to the surface of the aqueous solution, which contained L-alanine as a solute in pure water, via chemical bonding states analyses using x-ray photoelectron spectroscopy (XPS). Measurement of hydrogen ion exponent (pH level) of pure water during the atmospheric plasma exposure showed that the pH level decreased to be acidic, but the water temperature did not change. The C 1s XPS spectrum from the L-alanine after the plasma exposure to the aqueous solution showed the decomposition of the -COOH group and the formation of -C=O group.

Effect of dipotassium hydrogen phosphate on thermodynamic properties of glycine and l-alanine in aqueous solutions at different temperatures

Densities, ρ, speed of sound, u for glycine, l-alanine have been measured in aqueous solutions of dipotassium hydrogen phosphate (DKHP) ranging from 0.2, 0.4, 0.6 and 0.8mol·kg−1 at temperatures T=(288.15, 298.15, 308.15 and 318.15)K. The different parameters such as apparent molar volume, limiting apparent molar volume, transfer volume, partial molar expansibility have been derived from density data. Experimental speeds of sound data were used to estimate apparent molar adiabatic compressibility, limiting apparent molar adiabatic compressibility, transfer parameter and hydration number. These parameters have been discussed in the light of ion-ion and ion-solvent interactions.

Role of hydration in determining the structure and vibrational spectra of L-alanine and N-acetyl L-alanine N′-methylamide in aqueous solution: a combined theoretical and experimental approach

In this work we have utilized recent density functional theory Born-Oppenheimer molecular dynamics simulations to determine the first principles locations of the water molecules in the first solvation shell which are responsible for stabilizing the zwitterionic structure of L-alanine. Previous works have used chemical intuition or classical molecular dynamics simulations to position the water molecules. In addition, a complete shell of water molecules was not previously used, only the water molecules which were thought to be strongly interacting (H-bonded) with the zwitterionic species. In a previous work by Tajkhorshid et al. (J Phys Chem B 102:5899) the L-alanine zwitterion was stabilized by 4 water molecules, and a subsequent work by Frimand et al. (Chem Phys 255:165) the number was increased to 9 water molecules. Here we found that 20 water molecules are necessary to fully encapsulate the zwitterionic species when the molecule is embedded within a droplet of water, while 11 water molecules are necessary to encapsulate the polar region with the methyl group exposed to the surface, where it migrates during the MD simulation. Here we present our vibrational absorption, vibrational circular dichroism and Raman and Raman optical activity simulations, which we compare to the previous simulations and experimental results. In addition, we report new VA, VCD, Raman and ROA measurements for L-alanine in aqueous solution with the latest commercially available FTIR VA/VCD instrument (Biotools, Jupiter, FL, USA) and Raman/ROA instrument (Biotools). The signal to noise of the spectra of L-alanine measured with these new instruments is significantly better than the previously reported spectra. Finally we reinvestigate the causes for the stability of the Pπ structure of the alanine dipeptide, also called N-acetyl-L-alanine N′-methylamide, in aqueous solution. Previously we utilized the B3LYP/6-31G* + Onsager continuum level of theory to investigate the stability of the NALANMA4WC Han et al. (J Phys Chem B 102:2587) Here we use the B3PW91 and B3LYP hybrid exchange correlation functionals, the aug-cc-pVDZ basis set and the PCM and CPCM (COSMO) continuum solvent models, in addition to the Onsager and no continuum solvent model. Here by the comparison of the VA, VCD, Raman and ROA spectra we can confirm the stability of the NALANMA4WC due to the strong hydrogen bonding between the four water molecules and the peptide polar groups. Hence we advocate the use of explicit water molecules and continuum solvent treatment for all future spectral simulations of amino acids, peptides and proteins in aqueous solution, as even the structure (conformer) present cannot always be found without this level of theory.

Vacuum-Ultraviolet Electronic Circular Dichroism ofl-Alanine in Aqueous Solution Investigated by Time-Dependent Density Functional Theory

The electronic circular dichoism (ECD) of L-alanine in the vacuum-ultraviolet region was calculated for various optimized structures using time-dependent density functional theory (TDDFT) to assign the CD spectrum observed experimentally in aqueous solution down to 140 nm [Matsuo, et al. Chem. Lett. 2002, 826]. The structure of L-alanine in vacuo was optimized using density functional theory (DFT) at the B3LYP/6-31G* level. Its hydrated structure was optimized with nine water molecules (six and three around carboxyl and amino groups, respectively) using DFT and a continuum model (Onsager model). The dihedral angles of carboxyl and amino groups in the optimized hydrated structure differed greatly from those in the crystal and in nonhydrated structures optimized using a continuum model only. The ECD spectrum calculated for the hydrated structure had two successive positive peaks with molar ellipticities of about 2000 deg cm2 dmol(-1) at around 205 and 185 nm, which were close to those observed experimentally. These positive peaks were attributable to n pi* transitions of the carboxyl group, with the latter peak also influenced by the pi pi* transition of the carboxyl group that originates below 175 nm. A small negative peak observed at around 252 nm was also predicted from the hydrated structure. These results demonstrate that the hydrated water molecules around the zwitterions play a crucial role in stabilizing the conformation of L-alanine in aqueous solution and that TDDFT is useful for the ab initio assignment of ECD spectra down to the vacuum-ultraviolet region.

The VA and VCD spectra of various isotopomers of l-alanine in aqueous solution

Density functional theory (DFT) at the Becke 3LYP level has been used to calculate the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra of various deuterated species of l-alanine. The effect of replacing the methine hydrogen, CH1, the methyl group, CH3, and both the methine and methyl group hydrogens, CH1 and CH3, with the deuteriated species Cd1, Cd3 and Cd1 and Cd3 is investigated, both in H 2O and D 2O. The predicted results are then compared to the corresponding experimental spectra. Comparison of the experimental and calculated frequency shifts and intensity changes in the VA and VCD spectra are used as a check of the Becke 3LYP hybrid model to successfully reproduce these fine features in the VA and VCD intensities. Furthermore, several aspects of the isotopomers and the isotope effects on vibrational spectra are discussed in the light of the approximation, i.e., validity of Born–Oppenheimer approximation.

A comparison of aqueous solvent models used in the calculation of the Raman and ROA spectra of l-alanine

This paper presents a quantum description of L-alanine in aqueous solution predicting the Raman and Raman optical activity (ROA) spectra. We have investigated theoretically the chiral sensitive spectroscopic method of ROA as a probe for secondary structural features. We have utilized the Becke 3LYP/6-31G* description to determine the geometries and Hessians [Theoretical and Computational Genome Research, Plenum Press, New York, 1997, p. 225; J. Phys. Chem. B 102 (1998) 5899; Chem. Phys. 225 (2000) 165], and have calculated the Becke 3LYP/6-31G* level electric dipole–electric dipole polarizability derivatives. The electric dipole–magnetic dipole polarizability derivatives and electric dipole–electric quadrupole polarizability derivatives further required to obtain the ROA spectra have also been calculated. The Raman scattering and ROA spectral simulations for the various structures are compared with the experimentally measured spectra and previously reported spectral simulations. The combination of Raman and ROA spectroscopy is shown to be as sensitive to secondary structural changes as its sister combination of vibrational absorption and vibrational circular dichroism and thus offers a complementary source of information when investigating the secondary structural and chiral features of biomolecules.

Structures, vibrational absorption and vibrational circular dichroism spectra of L-alanine in aqueous solution: a density functional theory and RHF study

A detailed comparative study of structures, vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra has been carried out for the zwitterionic structure of the amino acid L-alanine. Theoretically determined structures necessary for deriving VA and VCD spectra were calculated with three different solvation approaches: the zwitterion surrounded by explicit water molecules only, the zwitterion embedded in a self-consistent reaction field (Onsager model) and the zwitterion plus the explicit water molecules embedded in a self-consistent reaction field. The structures were optimized at the density functional theory level using the B3LYP functional with the 6-31G* basis set. The Hessians and atomic polar tensors and atomic axial tensors were all calculated at the B3LYP/6-31G* level of theory. An important result is the method of treating solvent effects by both adding explicit water molecules and a dielectric media through the Onsager model and only this combination gave excellent comparison to experimental VA and VCD spectra. Two dominant conformers with different backbone configurations are identified, and the inclusion of solvent effects clearly favours one of the conformers. The calculated VA and VCD spectra of this conformer are in better agreement with experimentally measured VA and VCD spectra previously reported.

Potentiometric and spectroscopic study of copper(II) complexes with glycyl-glycyl- l-histidyl- l-alanine in aqueous solution

The complex formation between copper(II) and the tetrapeptide glycyl-glycyl- l-histidyl- l-alanine ([H 3L] 2+) has been studied in aqueous solution at t = 25°C and I = 0.1 mol dm −3 by potentiometric, visible spectrophotometric and circular dichroism measurements. All the experimental techniques show that the complex [CuLH −2] − is predominant over a wide pH range, while the monodentate [CuLH] 2+ is formed in the acidic region and a further deprotonated [CuLH −3] 2− species exists at pH higher than 10. The formation constants of the three above complexes are reported and a structure is proposed on the basis of spectroscopic results. The structure of [CuLH −2] − species very probably involves four nitrogen donors in the plane, excluding coordination by the l-alanine residue, while it seems likely that [CuLH −3] 2− is formed by simple dissociation of the N-1 pyrrole hydrogen.

Electronic spectral studies of nickel(II) alanine complexes

The electronic absorption spectrum of hydrated nickel(II) exhibits three bands, a broad band λ max at 658 nm and two sharp bands with λ max at 394 and 302 nm. The electronic absorption spectrum of Ni(II) and D- and L-alanine in aqueous solution shows the same three characteristic bands, but with λ max at 618,370 and 302 nm, with the absorption intensities increased for the first two bands. The three bands are assigned to the three spin-allowed d-d transitions 3A 2g → 3T 2g, 3A 2g → 3T 1g(F) and 3A 2g → 3T 1g(P) of octahedral nickel(II). Information about the Ni(II) complex formation mechanism and nature of the products was obtained from isosbestic points and pH profile studies of electronic spectra and amino acid racemization rates.

The partial molar enthalpies in aqueous solution of some amino acids with polar and non-polar side chains

The enthalpies of dilution of aqueous solutions of L-alanine, L-arginine, L-cysteine, glycine, L-serine, and L-valine have been measured by flow calorimetry, and used to calculate the partial molar enthalpies of the solution components. Partial molar entropies of water in the solutions were calculated using literature data for the activity of H 2O in the solutions. The partial molar enthalpies of H 2O in the solutions of amino acids with non-polar side chains were negative but in the solutions of amino acids with polar side chains and in glycine solutions they were positive.