title: 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.
abstract: 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. No current analytical methods can simultaneously determine AAR and AAI during the degradation of Aβ from AD patients. We now report a covalent chiral derivatized ultraperformance liquid chromatography tandem mass spectrometry (CCD-UPLC-MS/MS) method for the determination of post-translational AAR and AAI of N-terminal Aβ (N-Aβ1-5) in human brain tissues. When subjected to tryptic N-Aβ1-5 from post-translationally modified natural Aβ in focal brain tissues by the CCD procedure, it was monitored at m/z 989.6→637.0/678.9 during electrospray collision-induced dissociation. These N-Aβ1-5 fragments with l-aspartic acid (l-Asp), d-Asp, l-isoAsp, and d-isoAsp could be separated using the UPLC system with a conventional reversed-phase column and mobile phase. The quantification of these peptides was determined using a stable isotope [(15)N]-labeled Aβ1-40 internal standard. The CCD-UPLC-MS/MS assay of potential N-Aβ1-5 allowed for the discovery of the present and ratio levels of these N-Aβ1-5 sequences with l-Asp, d-Asp, l-isoAsp, and d-isoAsp.
authors.affiliation: Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka , Shizuoka, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Inoue
authors.forename: Daiju
authors.initials: D
authors.lastname: Hosaka
authors.forename: Nana
authors.initials: N
authors.lastname: Mochizuki
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Akatsu
authors.forename: Kaname
authors.initials: K
authors.lastname: Tsutsumiuchi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hashizume
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Matsukawa
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Toyo'oka
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000235:genetics* / Q000473:pathology; D016229:Amyloid beta-Peptides / Q000032:analysis / Q000235:genetics*; D001921:Brain / Q000473:pathology / Q000502:physiology*; D001923:Brain Chemistry / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D016229:Amyloid beta-Peptides