Cross-β-sheet supersecondary structure in amyloid folds: techniques for detection and characterization

The formation of protein aggregates is linked to the onset of several human disorders of increasing prevalence, ranging from dementia to diabetes. In most of these diseases, the toxic effect is exerted by the self-assembly of initially soluble proteins into insoluble amyloid-like fibrils. Independently of the protein origin, all these macromolecular assemblies share a common supersecondary structure: the cross-β-sheet conformation, in which a core of β-strands is aligned perpendicularly to the fibril axis forming extended regular β-sheets. Due to this ubiquity, the presence of cross-β-sheet conformational signatures is usually exploited to detect, characterize, and screen for amyloid fibrils in protein samples. Here we describe in detail some of the most commonly used methods to analyze such supersecondary structure.