(Gln22)-Amyloid _-Protein (1-40) is a Dutch mutation (E22Q) of amyloid _-peptide that aggregates more readily than the wild-type peptide, and the resulting fibrils show increased neurotoxicity. At the concentration of 25 _m, the mutant peptide E22Q could induce apoptosis of brain endothelial cells, but WT A_ 1-40 and the Italian mutant E22K had no significant effect on apoptosis.