Co-incubation of an amyloid protein with sulfated macromolecules as a method for the formation of amyloid plaques. The amyloid protein may be the beta-amyloid protein or the prion protein or the like. Amyoid plaque formation in one embodiment proceeds in vitro and desirably produces amyloid plaques that stain with Congo red and demonstrate a maltese-cross pattern when viewed under polarized light. The method also produces amyloid plaques that demonstrate an "amyloid star" appearance when viewed by transmission electron microscopy. An in vivo assay is also presented for selecting a candidate therapeutic agent for inhibiting or disrupting amyloid plaque deposition or persistence.