Immobilized amyloid-β protein experiments using SPR technology

the progression of Alzheimer’s disease. (AD), and the presence of amyloid plaques in the brain is an invariant feature of the disease. The primary component of these neuritic plaques is the amyloid-β (Aβ) protein, and its aggregation into plaques has been proposed to be a cause of AD neurodegeneration (Hardy and Higgins, 1992). The amyloid cascade hypothesis continues to be controversial, and the process of Aβ protein aggregation and its biological consequences remains the subject of intense scrutiny (Rochet and Lansbury, 2000). Outstanding questions such as the thermodynamic basis for aggregation, the structure of the aggregates, the role of amyloid binding proteins, and the utility of inhibiting the aggregate’s toxic properties continue to drive the development of new methods. Biosensors that use immobilized Aβ for the study of amyloid-protein, amyloid-amyloid, and amyloidinhibitor interactions have all been reported. Each of these approaches have provided essential data for several aspects of amyloid interactions. Binding targets that are prone to aggregation in solution present inherent problems for the development of binding assays. Results from solution assays may be difficult to interpret if the aggregation state of the binding target is not constant over the course of the experiment. Additionally, if multiple preparations of the protein are to be used, the aggregation state must remain constant between experiments to maintain reproducibility. Both of these problems can be avoided by immobilization of the aggregating species, either in a disaggregated form or as an aggregate (Table 1). Immobilization maintains site isolation of the aggregating species, and in some cases the surfaces can be regenerated for multiple experiments. The current literature provides instructive examples for the use and construction of amyloid binding assays for identifying Aβ binding proteins, studying Aβ aggregation, and identifying Aβ-binding small molecules.