Neutron Scattering Reveals Enhanced Protein Dynamics in Concanavalin A Amyloid Fibrils

Protein aggregation is one of the most challenging topics in life sciences, and it is implicated in several human pathologies. The nature and the role of toxic species is highly debated, with amyloid fibrils being among the most relevant species for their peculiar structural and functional properties. Protein dynamics and in particular the ability to fluctuate through a large number of conformational substates are closely related to protein function. This Letter focuses on amyloid fibril dynamics, and, to our knowledge, it is the first neutron scattering study on a protein (Concanavalin A) isolated in its fibril state. Our results reveal enhanced atomic fluctuations in amyloid fibrils and indicate that the protein is "softer" in the fibril state with respect to the native and amorphous aggregate states. We discuss this finding in terms of a structural interpretation and suggest that the paradigm ordered structure <-> lower flexibility can be questioned when considering the local fast side-chain protein dynamics.