Amyloid β-Protein (1-42)

Aβ 1-42, 42-residue fragment of amyloid precursor protein, has been found to be a major constituent of the senile plaques formed in the brains of patients with Alzheimer’s disease and late Down’s syndrome. Aβ 1-42 readily forms neurotoxic oligomers at physiological pH. On the other hand, the peptide shows antimicrobial activity. The sequence of this peptide corresponds to the sequence of human, bovine, canine, feline, ovine, guinea pig, and rabbit Aβ42. The peptide has been used to detect amyloid β-protein multimers in the cerebrospinal fluid of Alzheimer’s disease patients through fluorescence correlation spectroscopy. For detailed descriptions of the preparation of Aβ 1-42 monomers and protofibrils please see the papers of Jan, Hartley, and Lashuel, Stine et al. (2011), and of Broersen and colleagues. For the preparation of Aβ for experimental use, Fezoui et al. (2000) found that solvation of synthetic peptide with sodium hydroxide (Aβ·NaOH) followed by lyophilization, produced stocks with superior solubility and fibrillogenesis characteristics. Solubilization of the pretreated material with neutral buffers resulted in a pH transition from ≈10.5 to neutral, avoiding the isoelectric point of Aβ (pI≈5.5), at which Aβ precipitation and aggregation propensity are maximal.