Cu binding interactions with AβPP and Aβ42. a) Configuration of Cu with residues His147, His151, Tyr168 in APP’s copper binding region and two water molecules in a trigonal bipyramidal geometry. b) Configuration of Cu with residues His388, His457, His507, and His511 in APP E2 domain. c) Cu binding with Aβ42 residues Ala2, His6, His13, and His14 in a tetrahedral square planar configuration. d) Cu binding to Aβ42 residues His6, Tyr10, His13, His14, and a water molecule in a trigonal bipyramidal configuration. e) Square-base pyramidal arrangement of Cu with Aβ42 residues Asp1, His6, His 13 or 14, and the carboxylate of Asp1, Glu3, Asp7, or Glu11.