PI3K-SH3 aggregation is representative of most amyloid aggregation reactions. In this work we introduce the methodology necessary to study the TSE of the amyloid fibril elongation reaction from a largely unstructured monomeric precursor . This is applicable to the majority of disease-related amyloid-forming proteins, such as Aβ peptide, tau and α-synuclein. The presented methodology constrains the endpoints of the reaction through seeding and subsequent controls (See Methods) to maximize the probability of the reaction pathway being unaltered upon mutagenesis.