Binding affinities for models of biologically available potential Cu(II) ligands relevant to Alzheimer's disease: an ab initio study.
A systematic study of the binding affinities of the model biological ligands X: = (CH3)2S, CH3S-, CH3NH2, 4-CH3-imidazole (MeImid), C6H5O-, and CH3CO2- to (NH3)i(H2O)3-iCu(II)-H2O (i = 3, 2, 1, 0) complexes has been carried out using quantum chemical calculations. Geometries have been obtained at the B3LYP/ 6-31G(d) level of theory, and binding energies, Delta, relative to H2O as a ligand, have been calculated at the B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d) level. Solvation effects have been included using the COSMO model, and the relative binding free energies in aqueous solution (Delta) have been determined at pH 7 for processes that are pH dependent. CH3S- (Delta = -16.0 to -53.5 kJ mol(-1)) and MeImid (Delta = -18.5 to -35.2 kJ mol(-1)) give the largest binding affinities for Cu(II). PhO- and (CH3)2S are poor ligands for Cu(II), Delta = 20.6 to -9.7 and 19.8 to -3.7 kJ mol(-1), respectively. The binding affinities for CH3NH2 range from -0.8 to -15.0 kJ mol(-1). CH3CO2- has Cu(II) binding affinities in the ranges Delta = -13.5 to -32.4 kJ mol(-1) if an adjacent OH bond is available for hydrogen bonding and Delta = 10.1 to -4.6 kJ mol(-1) if this interaction is not present. In the context of copper coordination by the Abeta peptide of Alzheimer's disease, the binding affinities suggest preferential binding of Cu(II) to the three histidine residues plus a lysine or the N-terminus. For a 3N1O Cu(II) ligand arrangement, it is more probable that the oxygen ligand comes from an aspartate/glutamate residue side chain than from the tyrosine at position 10. Methionine appears unlikely to be a Cu(II) ligand in Abeta.
Rickard
Gail A
GA
Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4.
Gomez-Balderas
Rodolfo
R
Brunelle
Patrick
P
Raffa
Duilio F
DF
Rauk
Arvi
A
D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000737:chemistry; D002151:Calorimetry; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008954:Models, Biological; D008968:Molecular Conformation; D058225:Plaque, Amyloid / Q000473:pathology
D016229:Amyloid beta-Peptides; D008024:Ligands; D003300:Copper; D006861:Hydrogen Peroxide