The thermodynamic activity of proline in ternary solutions of different water potentials.

The particular colligative properties of proline caused us to investigate the thermodynamic activity of this amino acid in detail. The dependence of the activity coefficients γ of proline (γ = thermodynamic activity/molality) on the pH of the solutions, the composition of the solution and the water potential has been measured. The results show that the activity coefficient of proline varies according to the solute milieu.