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This article presents mole fraction solubilities of L-tryptophan in binary aqueous methanol solvent systems and applied them to estimate thermodynamical parameters like transfer Gibbs free energetics and entropies of solutions. The estimated thermodynamic energies were linked with interaction parameters like dipole-dipole interactions, enthalpy due to transfer of L-tryptophan from water to binary water-methanol solvent mixtures. The transfer Gibbs free energetics for chemical interactions and entropies for solvent-solvent interaction were calculated by mathematical relations. The chemical transfer energetics was applied to explain the probable stability of L-tryptophan in the mixed solvents. Many associated thermophysical parameters were also calculated at standard temperature (298.15 K). Key words: L-tryptophan, aqueous methanol solution, solubility, chemical free energy, chemical entropy, 1. Introduction The function of biomolecules (like amino acid) in life and natural systems is very significant for their unusual properties. The side chains of different amino acids are responsible [...]

The solubility and thermodynamics of solvation due to solute-solvent interactions of glycine, DL-alanine, DL-serine, and DL-valine were determined in this study. Mainly, the transfer of Gibbs free energies from aqueous to aqueous sodium and potassium iodide salt solutions was considered, which were calculated by direct experimental solubility data and via theoretical calculations. The equilibrium solubilities were measured at 298.15 K using simple 'formol titration'. Various important physicochemical factors like enthalpy of solvation, molar volume, molar mass, molar density, etc., in aqueous electrolyte solutions were calculated at standard temperature. The thermodynamic parameters were explained to conclude about the virtual stability of the zwitterionic solutes in aqueous salt mixtures. The factors that are associated with solubility were also explained and correlated with physical and thermodynamic point of view. Key words: amino acids, sodium iodide, water, salting in effect, Gibbs free energies, 1. Introduction Solubility and associated thermodynamic parameters are extremely important for designing the mode of crystallization and separation of an amino acid from a mixture of amino acids and other [...]

In the current work, the analyti cal static gravimetric technique was used to assess the solubilities of DL-α-amino butyric acid and DL-valine in an aqueous binary solvent mixture of sodium sulfate (Na2SO4) under equilibrium saturation conditions in between temperature range 288.15 and 308.15 K. Different thermodynamic factors along with transfer Gibbs energetics and entropies under standard conditions were estimated by using computational as well as theoretical method by using the experimental solubilities. Several modes of interactions that occur during solvation were also explained. The manner that solvent molecules of solute amino acids are surrounded in the aforementioned medium employed during the process is taken into consideration. Amino acids become more soluble as the temperature rises. The study also helps us to reach the conclusion that physical properties of electrolyte (Na2SO4), mixed solvent, and the size of the amino acids' molecules are the main governing factors for the chemical stability as well as other thermodynamic and physical property like solubility of solute amino acids. [ABSTRACT FROM AUTHOR]