Alpha-synuclein's first sixty residues are built from imperfect eleven-residue KTKEGV repeats. Disordered in solution, they fold into an amphipathic helix on contact with acidic phospholipid membranes, and this is how the protein associates with synaptic vesicles. Residues 1 to 20 open that region. Nothing in this window drives aggregation. The amyloidogenic segment lies further along the chain, which makes the extreme N-terminus useful precisely because it is inert in that respect: it provides a sequence-matched comparator for experiments where a hydrophobic peptide might aggregate, adsorb or behave non-specifically, and a negative control that is genuinely part of the same protein rather than an unrelated sequence. The window is also biologically distinctive for another reason. Alpha-synuclein is N-terminally acetylated in cells, a modification that stabilises helical structure here and influences membrane affinity, so reagents and antibodies directed at this region may behave differently against acetylated and unmodified protein. The biotin carries a long-chain spacer, holding the sequence clear of a streptavidin surface where crowding would otherwise suppress binding signal. | 