The Nucleation of Lysozyme from a Fluctuation Point of View

The enzyme lysozyme is a useful model for the study of protein nucleation. The nucleation of lysozyme can be very well discussed in the framework of classical nucleation theory. However, the crystallization process develops differently below and above the critical temperature, Tc, of liquid−liquid phase separation. Above Tc, nucleation follows the line of the classical theory, but below Tc, nucleation is preceded by the growth of protein concentration fluctuations. This results in a relationship between the induction time vs. temperature curve and the left branch of the liquid−liquid phase separation curve. In fact, these two curves are equal. The transition in the nature of the nucleation process near Tc is in accordance with a principle proposed several years ago by Prigogine and colleagues.