PPIB and Alzheimer disease: Further evidence for a role of acidosis in AD comes from studies which have demonstrated that Αβ aggregates more avidly at pH 6.8 than pH 7.4 [89], and incubation of Αβ with Fe3-Citrate or Cu2-Glycine at pH 6.8 resulted in the production of more Fe2 and Cu1 than at pH 7.4 [47,90].