Citrullinated amyloid-β (1-42) peptide (human) (Citrullinated Aβ (1-42)) is a modified form of β-Amyloid (1-42) with a citrullination at the Arg5 site. Compared to the unmodified β-Amyloid (1-42), its formation of soluble low-molecular-weight oligomers is enhanced, the rate of fibril formation is reduced, and like unmodified Aβ42, it forms protofibrils comprised of parallel β-sheets.