Amyloid protein that folds clumps with other folded amyloid to form a plague. I think these plagues encourage Tau protein to clump forming Tau "tangles". These tangles are the bullet that kills the neuron. PBS doc on alzheimers last week described this theory. The amyloid plagues, I thnk, interfere with propagation of an electrical signal (action potential) from neuron to neuron. That means neurons can't effectively communicate with each other which impairs cognition. 2-73 prevents the folding of amyloid in the first place, whereas the antibody drugs just clean up the plagues AFTER they've already formed.