Simultaneous Determination of Post-Translational Racemization and Isomerization of N-Terminal Amyloid-尾 in Alzheimer鈥檚 Brain Tissues by Covalent Chiral Derivatized Ultraperformance Liquid Chrom

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• 作者：Koichi Inoue ; Daiju Hosaka ; Nana Mochizuki ; Hiroyasu Akatsu ; Kaname Tsutsumiuchi ; Yoshio Hashizume ; Noriyuki Matsukawa ; Takayuki Yamamoto ; Toshimasa Toyo鈥檕ka
• 刊名：Analytical Chemistry
• 出版年：2014
• 出版时间：January 7, 2014
• 年：2014
• 卷：86
• 期：1
• 页码：797-804
• 全文大小：391K
• ISSN：1520-6882

文摘

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鈥檚 disease (AD) is reliably related to the formation and aggregation of amyloid-尾 peptide (A尾) plaques in the human brain. No current analytical methods can simultaneously determine AAR and AAI during the degradation of A尾 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 A尾 (N-A尾_1鈥?) in human brain tissues. When subjected to tryptic N-A尾_1鈥? from post-translationally modified natural A尾 in focal brain tissues by the CCD procedure, it was monitored at m/z 989.6鈫?37.0/678.9 during electrospray collision-induced dissociation. These N-A尾_1鈥? 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 [¹⁵N]-labeled A尾_1鈥?0 internal standard. The CCD-UPLC-MS/MS assay of potential N-A尾_1鈥? allowed for the discovery of the present and ratio levels of these N-A尾_1鈥? sequences with l-Asp, d-Asp, l-isoAsp, and d-isoAsp.