Table 1.

Comparison of biofilament growth dominated by primary and secondary nucleation pathways. Primary nucleation processes create new aggregates at a rate that depends only on the concentration of monomeric peptide, whereas fragmentation creates new aggregates at a rate that depends only on the concentration of existing aggregates; monomer-dependent secondary nucleation creates new aggregates at a rate that depends on both the concentration of monomeric peptide and the concentration of existing aggregates. The dependencies of the latter two (secondary) nucleation processes on the existing aggregate concentration results in positive feedback: as the reaction proceeds, and proliferation through these mechanisms increases the concentration of aggregates, the rate at which these processes occur further is increased.

	Primary nucleation	Fragmentation	Monomer-dependent secondary nucleation
Kinetic parameters	λ, k+	λ, κ−, k+	λ, κ2, k+
Early time growth	Polynomial	Exponential	Exponential
Scaling behaviour (lag time, max growth rate)	Yes with λ	Yes with κ−	Yes with κ2
Positive feedback	No	Yes	Yes