Racemization of the aspartic acid residue of amyloid-β peptide by a radical reaction.

Human amyloid-β peptide 1-42 (Aβ) was subjected to a radical reaction by using ascorbic acid and CuCl(2). The percentage of D-aspartic acid (D-Asp) after 24 h had increased to 6.69 ± 0.09%, this being comparable with the reported D-Asp concentration of purified core amyloids in Alzheimer's disease patients. This racemization was significantly inhibited by radical scavengers. L-Alanine was also racemized during the same reaction.