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, VΦ, the apparent molar isentropic compressions, KS,Φ, 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.

► TMAO, glycine and its methyl derivatives in aqueous solutions were studied.
► The density and the speed of sound were measured for presented systems.
► Correlations between properties and group additivity are observed.
► The obtained data are compared with analogous values for urea and its derivatives.
► Correlation between volumetric and spectroscopic data is presented for discussed solutes.