Two additional ELISA plates were used: one plated with PHF extracted from a human AD brain and treated to maximize the number of clusters of β-sheet oligomeric conformers associated with the fibrils (Figs 3a and 4a) that have been reported to be associated with β-sheet steric zippers characteristic of toxic oligomerization before they become buried in fibril structures25, 26; and another plated with an aged elk recombinant PrP produced in E. coli. The gene discussed is PRNP; the disease is Alzheimer disease.