6D and 6P isoforms inhibit the polymerization of hTau40, as measured by laser-light scattering (LLS). (A) LLS was used to monitor the polymerization of hTau40 in the absence (●) or presence of a twice-molar excess of 2N6P (▲) and 2N6D (□). An N-terminal construct know to inhibit hTau40 polymerization, Tau1-196 (○), was included as an experimental control. (B) Representative electron micrographs of hTau40 filaments formed alone or in the presence of 8 μM 2N6P, 2N6D, or 1-196. Scale bar represents 500 nm.