L-serine In Aqueous Solutions Research Articles

Volumetric properties for glycine and l-serine in aqueous solutions of 1-Ethyl-3-methylimidazolium hydrogen sulfate ([Emim][HSO4]) at T = (293.15–313.15) K and ambient pressure

By using the volumetric properties, the solute–solvent interactions are studied in the ternary (glycine+1-Ethyl-3-methylimidazolium hydrogen sulfate [Emim][HSO4]+water) and (l-serine+1-Ethyl-3-methylimidazolium hydrogen sulfate [Emim][HSO4]+water) systems. For this purpose, the apparent molar volumes, Vφ, are calculated from the experimental density data. To obtain limiting apparent molar volumes Vφ0, the apparent molar volume values are fitted to the Redlich-Mayer type equation. Then the limiting apparent molar volumes of transfer, ΔVφ0, for studied amino acids from water to aqueous solutions of ionic liquid (IL) are calculated. The results showed that the ΔVφ0 values are negative for both ternary systems at all temperatures. The limiting apparent molar expansibility Eφ0 values have been obtained from the first derivative of limiting apparent molar volumes with respect to temperature. The values of second derivative of limiting apparent molar volumes respect to temperature show the structure making or breaking ability of glycine and l-serine in studied IL aqueous solutions. The results indicated that glycine and l-serine act as structure maker in studied solutions. McMillan–Mayer theory is used for evaluating the interaction parameters. Also the hydration number, nH, for both amino acids in ternary solutions has been reported.

The chemical stability of L-isoleucine, L-threonine, and L-serine in aqueous solutions of KCl at 298.15 K

The experimental saturated solubilities of L-isoleucine, L-threonine, and L-serine in aqueous mixtures of a KCl solution at 298.15 K are presented in this article. The solubilities are measured by gravimetric method. In the present study the theoretical calculation of the standard transfer Gibbs free energy, cavity forming enthalpy of transfer, cavity forming transfer Gibbs free energy, dipole-dipole interaction effect have been computed. The chemical effects of the transfer Gibbs energies for the present amino acids have been obtained by subtracting the cavity effects and dipole-dipole interaction effects from the ΔGt0(i). The stability of the experimental amino acids in aqueous KCl in terms of thermodynamic parameters is explained.

Hyperbranched polymers as phase forming components in aqueous two-phase extraction

This work focusses on the experimental and theoretical investigation of the partitioning of a l-serine in an aqueous two-phase system (ATPS) based on a hyperbranched polymer. As a model ATPS, a polymer system containing a hyperbranched polyesteramide and dextran was chosen. The partitioning of l-serine in this ATPS was studied and compared with the partitioning of l-serine in a conventional ATPS consisting of polyethylene glycol (PEG) and dextran. For the thermodynamic modelling of these ATPS’s the Lattice Cluster Theory (LCT) in combination with the Wertheim association theory was used. The LCT allows the incorporation of the hyperbranched polymer architecture in the Helmholtz free energy and the Wertheim association theory considers the influence of the polar groups. As a result, it can be stated that in both ATPS, l-serine is mainly partitioned into the dextran-enriched phase, but in the ATPS based on the hyperbranched polyesteramide and dextran, the l-serine concentration in the dextran-enriched phase is higher. The partitioning of l-serine could be predicted by the used thermodynamic model on basis of the solubility experiments carried out for l-serine in aqueous solutions of phase forming components. Further, this work represents the first application of the used thermodynamic model on a quaternary system.

Thermodynamic parameters of complexation reactions between nickel(II) ion and L-serine in aqueous solutions

A thermochemical study of coordination equilibria in the nickel(II) ions-L-serine system was carried out. The heats of reaction between solutions of an amino acid and nickel(II) nitrate at 288.15, 298.15, and 308.15 K and ionic strength of 0.25, 0.50, and 0.75 (KNO3) were measured. The heats of dilution of nickel nitrate solution in background electrolyte solutions were determined under identical conditions to make proper corrections. The results were processed with allowance for stepwise equilibria. The standard thermodynamic parameters of the complexation processes were calculated. The effect of temperature on heats of complexation reactions in the L-serine-nickel(II) ions was studied. The standard enthalpies of formation of NiSer+, NiSer2, and NiSer3− complexes in aqueous solutions were determined.

Volumetric Properties of l-Alanine and l-Serine in Aqueous N,N-Dimethylformamide Solutions at 298.15 K

The densities of l-alanine and l-serine in aqueous solutions of N,N-dimethylformamide (DMF) have been measured at 298.15 K with an Anton Paar Model 55 densimeter. Apparent molar volumes $$ (V_{\phi } ) $$ , standard partial molar volumes $$ (V_{\phi }^{0} ) $$ , standard partial molar volumes of transfer $$ (\Updelta_{\text{tr}} V_{\phi }^{0} ) $$ and hydration numbers have been determined for the amino acids. The $$ \Updelta_{\text{tr}} V_{\phi }^{0} $$ values of l-serine are positive which suggest that hydrophilic–hydrophilic interactions between l-serine and DMF are predominant. The –CH3 group of l-alanine has much more influence on the volumetric properties and the $$ \Updelta_{\text{tr}} V_{\phi }^{0} $$ have smaller negative values. The results have been interpreted in terms of the cosphere overlap model.

L-Serine in aqueous solutions at different pH: Conformational preferences and vibrational spectra of cationic, anionic and zwitterionic species

The aim of this study is to understand the conformational preferences of l-Serine (C3H7NO3, 2-amino-3-hydroxypropanoic acid) at different pH conditions. A conformational study in aqueous solution of the dissociation equilibrium of the polar amino acid l-Serine, was carried out for this purpose. We recorded, at room temperature, the Mid-IR, FarIR and Raman spectra of l-Serine from the aqueous solutions at pH values 5.82 (zwitterionic species), 1.00 (protonated species) and 13.00 (deprotonated species). Both the study of the conformational landscape and the theoretical analysis of the vibrational features were done using DFT and ab initio calculations, i.e. B3LYP/6-31+G(d,p), M062X/6-31+G(d,p) and MP2/6-31+G(d,p) levels of theory. The presence of water was included with the IEF-PCM implicit hydration model. Concerning the zwitterion, analysis of the low frequency region (700–50cm−1) in the FT-Raman and FarIR spectra reveals important information for assignment of the most stable structures.

Thermodynamic characteristics of protolytic equilibria of L-serine in aqueous solutions

The heat effects of the reaction of aqueous solution of L-serine with aqueous solutions of HNO3 and KOH were determined by calorimetry at temperatures of 288.15, 298.15, and 308.15 K, and ionic strength values of 0.2, 0.5, and 1.0 (background electrolyte, KNO3). Standard thermodynamic characteristics (Δr H o, Δr G o, Δr S o, ΔC o ) of the acid-base reactions in aqueous solutions of L-serine were calculated. The effect of the concentration of background electrolyte and temperature on the heats of dissociation of amino acid was considered. The combustion energy of L-serine by bomb calorimetry in the medium of oxygen was determined. The standard combustion and formation enthalpies of crystalline L-serine were calculated. The heats of dissolution of crystalline L-serine in water and solutions of potassium hydroxide at 298.15 K were measured by direct calorimetry. The standard enthalpies of formation of L-serine and products of its dissociation in aqueous solution were calculated.

Enthalpies of transfer of amino acids from water to aqueous solutions of N-methylacetamide and N, N-dimethylacetamide at T = 298.15 K

Enthalpies of solution of glycine, l-alanine and l-serine in aqueous solutions of N-methylacetamide and N, N-dimethylacetamide were measured at 298.15 K. Enthalpies of transfer (Δ tr H) of amino acids from water to aqueous solutions of amides were derived. It has been show that the enthalpies of transfer of amino acids are positive and increase with the increasing concentration of amides. The relative order of Δ tr H of amino acids in the same concentration of NMA or DMA is l-serine < glycine < l-alanine. The influence of side group of l-alanine and l-serine on Δ tr H has been discussed in terms of structural interaction. The results were compared with those in aqueous formamide, N-methylformamide and N, N-dimethylformamide solutions.

Enthalpies of transfer of amino acids from water to aqueous solutions of N-methylformamide and N, N-dimethylformamide at T = 298.15 K

Enthalpies of solution of glycine, l-alanine and l-serine in aqueous solutions of N-methylformamide and N, N-dimethylformamide were measured at 298.15 K. Enthalpies of transfer (Δ tr H) of amino acids from water to aqueous solutions of amides were derived and interpreted in terms of structural interaction. The results were compared with those in aqueous formamide solutions.

Interactions of DL-serine and L-serine with NaCl and KCl in aqueous solutions

The activity coefficients at 25‡C of DL-serine and L-serine in aqueous solutions of NaCl and KC1 were measured. This study examines the effect of the nature of the cation of the electrolyte on the activity coefficients of the optical-isomers of serine in aqueous solutions for molality of serine up to 0.4 and molality of electrolyte up to 1. An electrochemical cell with two ion-selective electrodes, a cation, and an anion ion selective electrode,vs. a double-junction reference electrode was used to measure the activity coefficients of the electrolyte and the results were converted to the activity coefficients of serine in the aqueous electrolyte solution. The comparison of the results obtained for DL- and L-serine indicates that the two optical isomers have identical interactions with electrolytes in aqueous solutions and that for this amino acid the effect of the cation of the electrolyte is not significant. Comparison of these results with previous measurements for DL-alanine in aqueous solutions of the same electrolytes show the notable effect of the backbone of the amino acid.