Fig. 4.

Relative timescales of nucleation and growth and the inferred assembly pathways. (A) Measured nucleation times (${\tau }_{\text{nuc}}$) and median growth times (${\tau }_{\text{grow}}$) at different protein concentrations. Error bars represent the SD from 3 replicate experiments. (B) Cartoon of the inferred assembly pathways. At low protein concentration, ${\tau }_{\text{nuc}}$ is large compared to ${\tau }_{\text{grow}}$, and a nucleus of coat proteins forms on the RNA and then grows into a proper capsid. At moderate protein concentration, ${\tau }_{\text{nuc}}$ is comparable to ${\tau }_{\text{grow}}$, and a second nucleus can form on the RNA before the first one has finished growing, leading to an overgrown structure consisting of a nearly complete capsid attached to a partial capsid. At high protein concentration, ${\tau }_{\text{nuc}}$ is smaller than ${\tau }_{\text{grow}}$, and multiple nuclei can form and grow, leading to an overgrown structure consisting of many partial capsids. Example TEM images of the endpoints of each pathway are shown at Right.