Binding of Zn(II), Cu(II), and Fe(II) ions to Alzheimer's A beta peptide studied by fluorescence

Binding of Zn(II), Cu(II) and Fe(II) ions to A beta 1-40, A beta 1-42 and a single tryptophan mutant of A beta 1-40 in solution at pH 7.4 was studied by fluorescent titration. Job plots and fitting of titration curves reveale d formation of 1:1 and 1:2 peptide-metal complexes. For dimeric peptides A beta 1-40 and A beta F4W the order of metal to peptide affinities is Fe < C u > Zn, which is in agreement with the Irving-Williams series of complex st ability. The affinity of A beta 1-42 for. Fe increases dramatically upon ag gregation: K-D changes from ca. 100 to ca. 0.2 mu M. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.