Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Vapour pressure measurements were applied to the systems guanidinium hydrochloride (methanamidine hydrochloride) + sodium L-glutamate (S-aminopenthanedioic acid sodium salt) + water at varying concentrations of GndmCl and Na-L-Glu, (m(NaGlu) = 0.1 - 1.6 mol/kg; m (GndmCl) = 0.104 mol/kg, 0.301 mol/kg, 0.684 mol/kg) for two temperatures, T = 298.15 K and 310.15 K. From the experimental results, activities of water, activity coefficients of water and the corresponding osmotic coefficients of the mixtures Na-L-Glu + GndmCl + water have been calculated, both being directly related to the chemical potentials of the different components and therefore to their Gibbs energy. The modeling of the components' chemical potentials in ternary GndmCl + Na-L-Glu + water solutions was done with the equation of state ePC-SAFT. Osmotic coefficients, fugacity coefficients and activity coefficients of the mixture components were modeled. Experimental osmotic coefficients values demonstrate non-linear concentration dependences with several extremums at different NaGlu molalities. Theoretical ePC-SAFT approach correctly describes the experimental data. Negative values of binary interaction parameters between the guanidinium ion and the amino acid salt were required in order to model osmotic coefficients of ternary systems salt + amino acid salt + water in good agreement with the experimental data, which shows that the nonCoulomb short-range interactions between ion and amino acid salt are very strong. 1. INRODUCTION Quantitative thermodynamic information concerning specific ion binding on biomolecules is necessary in various medical, pharmaceutical and industrial applications [1,2]. Proteins build not only cell body, they decide also on genetic information transfer, metabolism and outside signal retreatment. As a result, nerve cells can communicate to each other and with other cell types. Sodium glutamate is especially important in the system of nerve impulse transmission [3, 4]. Specific ion effects cause formation of modified biological structures and self-associated aggregates in protein solutions. In spite of many experimental examples, a profound understanding of these basic effects and their reasons has been developed only in very recent years. Extraordinary complexity of protein solutions requires firstly the establishment of general rules governing specific ACS Paragon Plus Environment