The researchers explicitly investigated the so-called crystal nucleation rate J(T). This is a measure of the probability that a crystal will form in a certain volume within a certain time.

In both cases no special care is taken with regard to nucleation and the parameter of time.

Figure 1: Model of Spir and Cappuccino cooperation in actin nucleation/polymerization. Together these findings establish actin nucleation by multiple WH2 domains as a general mechansim.