The dimeric and tetrameric octarepeat fragments of prion protein behave differently to its monomeric unitElectronic supplementary information (ESI) available: Figs. a–e: Distribution profiles of free and complexed fractions of Cu2+ions with ligands in competition studies. See http://www.rsc.org/suppdata/dt/b4/b402090a/

Potentiometric and spectroscopic data have shown that octarepeat dimer and tetramer are much more effective ligands for Cuii ions than simple octapeptide. Thus, the whole N-terminal segment of prion protein due to cooperative effects, could be more effective in binding of Cuii than simple peptides containing a His residue. The gain of the Cuii binding by longer octarepeat peptides derives from the involvement of up to four imidazoles in the coordination of the first Cuii ion. This type of binding increases the order of the peptide structure, which allows successive metal ions for easier coordination.