Simultaneous determination of post-translational racemization and isomerization of N-terminal amyloid-β in Alzheimer's brain tissues by covalent chiral derivatized ultraperformance liquid chromatography tandem mass spectrometry.

Typical markers of protein aging are spontaneous post-translational modifications such as amino acid racemization (AAR) and amino acid isomerization (AAI) during the degradation of peptides. The post-translational AAR and AAI could significantly induce the density and localization of plaque deposition in brain tissues. Alzheimer's disease (AD) is reliably related to the formation and aggregation of amyloid-β peptide (Aβ) plaques in the human brain.