MAPT and Alzheimer disease: They both have sufficient affinity for tau (AD-PHF) 14.6 nM and 22nM based on a Scatchard analysis of autoradiography staining of human PHF-AD brain sections, with Kd(Aβ)/Kd(tau) 25 and 27 respectively, meaning a higher selectivity of tau aggregates over Aβ fibrils (Table 2).