Thermodynamic Properties of l-Aspartates of Alkali and Alkali-Earth Metals in Aqueous Solutions at 298.15 and 310.15 K and Specific Cation Effects on Biomolecule Solvation
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Vapor pressure osmometry was applied to the systems calcium l-aspartate ((S)-aminobutanedioic acid calcium salt) + water for varying molalities of Ca–l-Asp (mCa–l-Asp = 0.01–1.02 mol·kg−1) and guanidinium hydrochloride (methanamidine hydrochloride) + sodium L–aspartate ((S)–aminobutanedioic acid sodium salt) + water, varying the molalities of GndmCl and Na–l-Asp (mNa–l-Asp = 0.1, 0.25, 0.4, 0.57 mol·kg−1 and mGndmCl = 0.1–1.1 mol·kg−1) at T = 298.15 K and 310.15 K. From vapor pressure osmometry, activities of water, and the corresponding osmotic coefficients of the mixtures Ca–l-Asp + water and Na–l-Asp + GndmCl + water have been calculated, both being directly related to the chemical potentials of the different species and therefore to their Gibbs energy. Mean molal ion activity coefficients were obtained from experimental data fits with the Pitzer equations and the corresponding dual and triple interaction parameters were derived for the Ca–l-Asp + water binary system. β(2) Pitzer parameters different from zero are required for Ca–l-Asp in water to reproduce the osmotic coefficient decrease with increasing concentration. Mean Spherical Approximation parameters accounting for Coulomb and short range interactions that describe the calcium and magnesium aspartates and glutamates are given. The decrease in the chemical potential of the aspartates corresponds to the Hofmeister series: NaAsp > Mg(Asp)2 > CaAsp. A strong interaction between amino acid and salt due to specific dispersion interactions in amino acid salt systems containing guanidinium based salt has been revealed that is in agreement with MD and half-empirical quantum-chemical calculations.
KeywordsVapor pressure osmometry Osmotic coefficient Calcium l-aspartate Sodium l-aspartate Guanidinium hydrochloride Electrolyte Activity coefficient
Funding was provided by Scientific-research theme of fundamental studies of Ministry of Education and Science of Ukraine, financed from the state budget of Ukraine. The authors would like to acknowledge gratefully Prof. Vasiliy I. Larin for the permanent help on this research, Olena S. Bondareva, Olesja O. Kulinich for taking part in the experiments.
- 1.Prausnitz, J.M., Lichtenthaler, R.N., de Azevedo, E.G.: Molecular Thermodynamics of Fluid-Phase Equilibria, 3rd edn. Prentice-Hall, Upper Saddle River (1999)Google Scholar
- 2.Kunz, W. (ed.): Specific Ion Effects. World Scientific, London (2010)Google Scholar
- 3.Duclohier, H. (ed.): Biophysics of Ion Channels and Diseases. Research Signpost, Kerala (2010)Google Scholar
- 7.Tsurko, E.N., Neueder, R., Kunz, W.: Activity of water, osmotic and activity coefficients of sodium glutamate and sodium aspartate in aqueous solutions at 310.15 K. Acta Chim. Slov. 56, 58–64 (2009)Google Scholar
- 11.Barthel, J., Neueder, R.: Precision apparatus for the static determination of the vapor pressure of solutions. GIT Fachz. Lab. 28, 1002–1012 (1984)Google Scholar
- 15.Pitzer, K.S. (ed.): Activity Coefficients in Electrolyte Solutions, 2nd edn. CRC Press, Boca Raton, pp. 75–153 (1991)Google Scholar
- 16.Keenan, J.H., Keyes, F.G., Hill, P.G., Moore, J.G.: Steam Tables: Thermodynamic Properties of Water Including Vapor, Liquid, and Solid Phases. Wiley, New York (1969)Google Scholar
- 23.Blum, L.: In: Henderson, H., Eyring, D. (eds.) Theoretical Chemistry: Advances and Perspectives, vol. 5, Academic Press, New York (1980)Google Scholar
- 24.Krestov, G.A.: Thermodynamics of Ionic Processes in Solutions. Khimija, Leningrad (1984)Google Scholar
- 27.Barrett, G.C. (ed.): Chemistry and Biochemistry of the Amino Acids. Chapman and Hall, London (1985)Google Scholar