Interaction between soluble Aβ-(1-40) monomer and Aβ-(1-42) fibrils probed by paramagnetic relaxation enhancement.

The most common isoforms of amyloid-β (Aβ) proteins are composed of 40 or 42 amino acid residues. While Aβ-(1-40) is the predominant species, Aβ-(1-42) is more fibrillogenic and neurotoxic, suggesting that Aβ-(1-42) plays a critical role in the initiation of amyloid fibril formation. We investigated the mechanisms by which soluble Aβ-(1-40) associates with preformed Aβ-(1-42) seeds. A paramagnetic relaxation enhancement analysis showed that the Aβ-(1-40) monomer and Aβ-(1-42) seed interact via their C-terminal region in a parallel fashion, and the N-terminal part does not to contribute to the interaction.