The NAC region, roughly residues 61 to 95, is what makes alpha-synuclein aggregate. Beta-synuclein lacks part of this stretch and does not assemble comparably, which is the clearest natural demonstration that the segment is the determining factor. This peptide runs from residue 51 into the start of it. Hydrophobic residues within NAC have been shown to drive formation of seed-competent fibrils — the species able to template further aggregation rather than merely existing as aggregate — and the region is the target of peptide inhibitors designed to interrupt templating. Work here therefore concerns aggregation kinetics, seeding and inhibitor design rather than the membrane biology that dominates the N-terminal peptides. One consequence deserves anticipating: a peptide reaching into the hydrophobic core can itself aggregate under some conditions. Solubility, storage and the aggregation state at the time of use are variables here in a way they are not for the N-terminal members of this series, and characterising the material as applied is worth doing rather than assuming a monomeric starting point. | 