Measurement of Interpeptidic Cu^II Exchange Rate Constants of Cu^II-Amyloid-? Complexes to Small Peptide Motifs by Tryptophan Fluorescence Quenching

The interpeptidic CuII exchange rate constants were measured for two Cu amyloid-? complexes, Cu(A?1–16) and Cu(A?1–28), to fluorescent peptides GHW DAHW using a quantitative tryptophan fluorescence quenching methodology. second-order determined at three pH values (6.8, 7.4, 8.7) important the Cu(A?) coordination components Cu(A?)I Cu(A?)II. constant is approximately 104 M–1 s–1 but varies in magnitude depending on many variables. These include pH, length of A? peptide, location anchoring histidine ligand number amide deprotonations required peptide coordinate CuII, interconversion between We also present EPR data probing formation ternary species GHW. As nonfluorescent GHK DAHK are motifs found blood serum, their ability sequester ions from complexes may be relevant metal homeostasis its implication Alzheimer’s disease. Thus, kinetic chemical that can help elucidate complex trafficking puzzle synaptic cleft.