Hydrogen/deuterium exchange mass spectrometry--a window into amyloid structure.

The beta-sheet network of the amyloid fibril is a dominant structural feature of this class of protein structures. An attractive way to view the protein misfolding events that lead to the formation of fibrils and other aggregates is to consider how native protein secondary structure rearranges to yield the H-bonding relationships within the aggregate structure. We describe here the application of hydrogen-deuterium exchange mass spectrometry (HX-MS) methods to probe the secondary structure of protein aggregates. This includes exploration of the structures of monomers, protofibrils, and fibrils, the structural relationships among these states, the energetic contribution of H-bonding to fibril stability, and the plasticity of the H-bond network.