Side Effect of Tris on the Interaction of Amyloid β-peptide with Cu2+: Evidence for Tris–Aβ–Cu2+ Ternary Complex Formation

Yannan Bin, Zhongxiu Jiang, Juan Xiang

The interaction of amyloid β-peptide (Aβ) with Cu(2+) is crucial to the development of neurotoxicity in Alzheimer's disease (AD). Many recent studies show a variation on the dissociation constant of Aβ-Cu(2+) under different solvent conditions. Among various buffers, the Tris(hydroxymethyl)aminomethane (Tris) buffer is the most reliable chelator of Cu(2+). However, as a typical nucleophilic reagent capable of binding peptides, the behavior of Tris should be more complicated. In this work, the effect of Tris on the interaction of Aβ with Cu(2+) was investigated. Under acidic conditions, Tris-Aβ-Cu(2+) ternary complex was identified by electrospray ionization mass spectrometry and transmission electron microscopy. The results of surface plasmon resonance reveal that the formation of the ternary complex increases the dissociation constant by almost 1 order of magnitude. Consequently, the assessment of toxicity indicates that the generation of · OH induced by the Aβ-Cu(2+) complex was enhanced in the presence of Tris. The work reveals the significant side effect of Tris on the interaction of Aβ with Cu(2+), which will greatly improve the quantitative investigation on Aβ-Cu(2+) interaction and be helpful for the in-depth understanding of the roles of Aβ and Cu(2+) in AD neuropathology.