The hydration of the protein stabilizing agents: Trimethylamine-N-oxide, glycine and its N-methylderivatives - The volumetric and compressibility studies

The densities at T = (288.15, 293.15, 298.15, 303.15, and 308.15) K and sound velocities at T = 298.15 K have been measured for aqueous solutions of trimethylamine-N-oxide, glycine, N-methylglycine (sarcosine), N,N-dimethylglycine, N,N,N-trimethylglycine (betaine). From these data the apparent molar volumes, V-Phi, the apparent molar isentropic compressions, K-S,K-Phi, and the solvation numbers of solutes have been determined. The concentration dependencies of the calculated quantities and their limiting values are discussed in terms of solute-solvent and solute-solute interactions. The obtained quantities are compared with the analogous data for urea and its derivatives. These two groups of osmolyties (stabilizers and denaturants of the proteins) reveal clearly different volumetric and compression features. (C) 2013 Elsevier Ltd. All rights reserved.