The speeds of sound and densities of different concentrations of L.-tyrosine + L-glutamic acid + water ternary solutions, L-tyrosine + water and L-glutamic acid + water binary solutions at T = (298.15,308.15,318.15) K have been measured. Using the densities and the speeds of sound, the apparent molar volumes, the apparent molar isentropic compressibilities, the limiting apparent molar volume, the limiting apparent molar compressibility, the constants (S-V,S-S, S-V,S-K, S-K,S-S and S-K,S-E) and the hydration number have been calculated. These parameters have been used to analyze the possible interionic interactions, such as ion-ion, solute-solvent, solvent-solvent, ion-solvent, and solute-co-solute interactions, and are discussed in terms of hydrophobic-hydrophobic, and hydrophilic-hydrophobic group interactions as well as, structure-making and structure-breaking effects in L-tyrosine + L-glutamic acid + water. (C) 2014 Elsevier B.V. All rights reserved.