Studies of solute solvent interactions

Abstract

Densities (and#961;) and speeds of sound (u) have been measured of (L-leucine / L-isoleucine / L-glutamine / L-alanine / glycylglycine + 0.512 mol.kg-1 aqueous K2SO4 / KNO3) solutions as a function of molal concentration of amino acid / peptide at different temperatures: (298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K. The measured density values exhibit usual increasing trend with an increase in molal concentration of solutions and decreasing trend with an increase in temperature for the systems under investigation. Using density data, the apparent molar volumes ( ) and the partial molar volumes ( ) of L-leucine, L-isoleucine, L-glutamine, L-alanine and glycylglycine in 0.512 mol.kg-1 aqueous K2SO4 / KNO3 solutions have been calculated. The observed values of the studied amino acid / peptide in said aqueous electrolyte solutions have been found to be positive and larger in magnitude than those of corresponding values in aqueous medium. The larger values of of L-leucine / L-isoleucine / L-glutamine / L-alanine / glycylglycine in 0.512 mol kg-1 aqueous K2SO4 / in 0.512 mol kg-1 aqueous KNO3 solutions than the corresponding values in aqueous medium have been ascribe to the following interactions occuring in solutions: newline(i) ion-ion interactions between the K+, SO42-, NO3- ions and (COO- , NH3+) newlinezwitterionic end groups (ii) ion-hydrophilic interactions between ions and hydrophilic groups (-CONH2-, CONH) of amino acid / peptide (iii) ion-non polar group interactions occurring between ions and the non-polar groups newline(-CH2 / -CH3) of amino acid / peptide. The trends of variations of values of L-leucine / L-isoleucine / L-glutamine / L-alanine / glycylglycine in 0.512 mol.kg-1 aqueous K2SO4 or 0.512 mol.kg-1 aqueous KNO3 solutions is found to be as: L-leucine gt L-isoleucine gt L-glutamine gt glycylglycine gt L-alanine newlineThe transfer partial molar volumes of L-leucine / L-isoleucine / L-glutamine / L-alanine / glycylglycine from water to 0.512 mol.kg-1 aqueous K2SO4 / KNO3 solutions have been calculated. The and#8710;tr values of L-l