The aggregation of beta-amyloid peptide (A beta) into fibrils plays an important role in the pathogenesis of Alzheimer's disease (AD). Metal ions including copper and zinc are closely connected to the precipitation and toxicity of A beta. In this study, a surface plasmon resonance (SPR) biosensor was constructed to investigate the interactions between A beta and metal ions. A beta peptide was immobilized on the SPR chip surface through a preformed alkanethiol self-assembled monolayer (SAM). Our observations indicate that the immobilized A beta undergoes a conformational change upon exposure to the metal ions. A difference in metal binding affinity between A beta(1-28) and A beta(1-42) was also detected. The results suggest that SPR is an effective method to characterize the interactions between A beta and metal ions.