A non-linear differential equation expressing the new phase nucleation rate in the different
steps of the process (non-stationary and stationary nucleation and in the plateau region) is
derived from basic principles of the nucleation theory. It is shown that one and the same
sigmoid (logistic) function describes both nucleation scenarios: the one according to the
classical theory, and the other according to the modern two-stage mechanism of protein
crystal formation. Comparison to experimental data on both insulin crystal nucleation …