Acoustic nonlinearity parameter B/A of aqueous solutions of some amino acids and proteins

A precision ultrasonic velocimeter and a new differential method of calculation of specific concentration increments were employed to study the nonlinear acoustic properties of aqueous solutions of ten amino acids and six proteins. The greater precision of the velocity measurements allows much more dilute solutions to be treated, providing for a wider range of amino acids and proteins to be studied. The specific increment of B/A of amino acids was found to exhibit a significant sensitivity to change of position or replacement of a single atomic group of the solute molecule. A strong influence of the character of the solute–solvent interaction on the B/A value is revealed. It is shown that the specific increment of B/A of a solute could be much more sensitive to the molecular structural features than other parameters such as the specific increments of sound velocity and density.