Biomolecular absorption of ultrasound. III. Solvent interactions

Absorption coefficients for several biomolecules have been measured to determine the role of solvent interactions in the absorption characteristics of biomolecules at neutral pH. The presence of phosphate buffer ions in aqueous solvent dramatically increases the absorption of small biomolecules (sugars and amino acids). These increases suggest the importance of solvent interactions in absorption. For large molecules (proteins and polysaccharides), buffer ion effects are lessened and the role of solvent interactions is not as clear. Absorptions of hemoglobin are essentially the same in each of five aqueous solvents and are greater in nonaqueous solvents. Solvation interactions may be inhibited by the tertiary structure of globular proteins. Solvation apparently does contribute to absorption in biomolecules along with other physicochemical processes.