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Dr. Sherif Ibrahim Metwally Ramadan :: Publications:

Title:
Synthetic standard aided quantification and structural characterization of amyloid-beta glycopeptides enriched from cerebrospinal fluid of Alzheimer’s disease patients
Authors: Jonas Nilsson, Gunnar Brinkmalm, Sherif Ramadan, Lisa Gilborne, Fredrik Noborn, Kaj Blennow, Anders Wallin, Johan Svensson, Mohamed A Abo-Riya, Xuefei Huang, Göran Larson
Year: 2019
Keywords: Not Available
Journal: Scientific reports
Volume: 9
Issue: 1
Pages: 5522
Publisher: Nature Publishing Group
Local/International: International
Paper Link:
Full paper Not Available
Supplementary materials Sherif Ibrahim Metwally Ramadan_41598_2019_41897_MOESM1_ESM.pdf
Abstract:

An early pathological hallmark of Alzheimer’s disease (AD) is amyloid-β (Aβ) deposits in the brain, which largely consist of up to 43 amino acids long Aβ peptides derived from the amyloid precursor protein (APP). We previously identified a series of sialylated Tyr-10 O-glycosylated Aβ peptides, 15–20 residues long, from human cerebrospinal fluid (CSF) and observed a relative increase of those in AD vs non-AD patients. We report here on the synthesis and use of an isotopically double-labeled Aβ1-15 glycopeptide, carrying the core 1 Galβ3GalNAcα1-O-Tyr-10 structure, to (1) identify by HCD LC-MS/MS the definite glycan core 1 structure of immunopurified and desialylated Aβ glycopeptides in human CSF and to (2) establish a LC-MS/MS quantification method for desialylated Aβ1-15 (and Aβ1-17) glycopeptides and to (3) compare the concentrations of these Aβ glycopeptides in CSF from 20 AD patients and 20 healthy controls. Although we unambiguously identified the core 1 structures and Tyr-10 attachment sites of the glycopeptides, we did not observe any quantitative differences, determined through both peptide and oxonium ion fragments, of the desialylated Aβ1-15 or Aβ1-17 glycopeptides between the AD and non-AD group. The new quantitative glycoproteomic approach described, using double-labeled glycopeptide standards, will undoubtedly facilitate future studies of glycopeptides as clinical biomarkers but should also embrace sialylated Aβ standards to reveal specific sialylation patterns of individual Aβ glycopeptides in AD patients and controls.

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