Different zinc(II) complex species and binding modes at Aβ N-terminus drive distinct long range cross-talks in the Aβ monomers

The present study addresses the reconstruction of the free-energy landscapes of amyloid-beta1-42 (Aβ42) coor- dinated respectively with one and two zinc ions, to scrutinize whether different Aβ–zinc complex species, i.e., mononuclear and dinuclear metal complexes, induce different Aβ conformation features.We found a subtle switch of intramolecular interactions, depending both on the zinc coordination environment and on the peptide to zinc stoichiometric ratio. On the one side, hairpin-like structures are predominant in mono- nuclear complexes, where a salt-bridge that involves Lys28-Glu22 and Lys16-Asp23 is stabilized. On the other side, elongated conformations are instead stabilized in the dinuclear zinc complexes. Experimental studies of atomic force microscopy as well as of zinc–Aβ complex species distribution diagrams provide evidence that the theoretical calculations can be rationalized in terms of the correlation between the increased amount of amorphous aggregates and theAβ/Zn2 + ratio.