Fig. 3.

(A) The free energy barrier $\mathrm{\Delta }{F}_c$ for conversion of one random coil peptide into the β-form within a disordered oligomer of the size N for various values of interpeptide interaction. From top to bottom, ${\mathit{ϵ}}_{ss}=3,\hspace{0.17em}4,\hspace{0.17em}5,\hspace{0.17em}6,\hspace{0.17em}8,\hspace{0.17em}\text{and}\hspace{0.17em}10kT$. In all cases, ${\mathit{ϵ}}_{s\beta }={\mathit{ϵ}}_{ss}+1kT$. (B) Partition of the free energy barrier for nucleation from solution. The red line and red squares show free energy for oligomerization, $\mathrm{\Delta }{F}_o\left(N\right)$, obtained from the oligomer size distribution $P\left(N\right)$ (shown in Inset) at $c=2.17$ mM and ${\mathit{ϵ}}_{ss}=6kT$. The blue line and blue circles show free energy for conversion of one peptide into the β-prone state within an oligomer of size N, $\mathrm{\Delta }{F}_c\left(N\right)$, for ${\mathit{ϵ}}_{ss}=6kT$ and ${\mathit{ϵ}}_{s\beta }=7kT$. Note that the blue line in B corresponds to the blue line in A. The violet line and violet diamonds show the free energy barrier for formation of a critical nucleus from solution, $\mathrm{\Delta }{F}^{\mathrm{\ast }}$, at $c=2.17$ mM and ${\mathit{ϵ}}_{ss}=6kT$ obtained as $\mathrm{\Delta }{F}^{\mathrm{\ast }}=\mathrm{\Delta }{F}_o\left(N\right)+\mathrm{\Delta }{F}_c\left(N\right)$.