The most prominent feature of the TSE is the 13 residue-stretch between positions 49 and 62 where the TSE shows essentially fully formed fibril-like contacts. Situated at the centre of the fibrillar core, this region represents the most deeply buried part of the interface due to the staggered arrangement of fibril units. Consequently, it is a region which establishes numerous intra-chain and inter-chain contacts in the final fibril state. These 13 residues appear to serve as the main misfolding nucleus, the structure of which the corresponding sequence stretches of all incorporating monomers will have to adopt.