%0 Journal Article
%A Pattky, Martin
%A Nicolardi, Simone
%A Santiago-Schübel, Beatrix
%A Sydes, Daniel
%A van der Burgt, Yuri E. M.
%A Klein, Antonia N.
%A Jiang, Nan
%A Mohrlüder, Jeannine
%A Hänel, Karen
%A Kutzsche, Janine
%A Funke, S. A.
%A Willbold, D.
%A Willbold, S.
%A Huhn, C.
%T Structure characterization of unexpected covalent O-sulfonation and ion-pairing on an extremely hydrophilic peptide with CE-MS and FT-ICR-MS
%J Analytical and bioanalytical chemistry
%V 407
%N 22
%@ 0016-1152
%C Berlin
%I Springer
%M FZJ-2015-06891
%P 6637 - 6655
%D 2015
%X In this study, we characterized unexpected side-products in a commercially synthesized peptide with the sequence RPRTRLHTHRNR. This so-called peptide D3 was selected by mirror phage display against low molecular weight amyloid-β-peptide (Aβ) associated with Alzheimer’s disease. Capillary electrophoresis (CE) was the method of choice for structure analysis because the extreme hydrophilicity of the peptide did not allow reversed-phase liquid chromatography (RPLC) and hydrophilic interaction stationary phases (HILIC). CE-MS analysis, applying a strongly acidic background electrolyte and different statically adsorbed capillary coatings, provided fast and efficient analysis and revealed that D3 unexpectedly showed strong ion-pairing with sulfuric acid. Moreover, covalent O-sulfonation at one or two threonine residues was identified as a result of a side reaction during peptide synthesis, and deamidation was found at either the asparagine residue or at the C-terminus. In total, more than 10 different species with different m/z values were observed. Tandem-MS analysis with collision induced dissociation (CID) using a CE-quadrupole-time-of-flight (QTOF) setup predominantly resulted in sulfate losses and did not yield any further characteristic fragment ions at high collision energies. Therefore, direct infusion Fourier transform ion cyclotron resonance (FT-ICR) MS was employed to identify the covalent modification and discriminate O-sulfonation from possible O-phosphorylation by using an accurate mass analysis. Electron transfer dissociation (ETD) was used for the identification of the threonine O-sulfation sites. In this work, it is shown that the combination of CE-MS and FT-ICR-MS with ETD fragmentation was essential for the full characterization of this extremely basic peptide with labile modifications.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000360220800009
%$ pmid:26123437
%R 10.1007/s00216-015-8826-8
%U https://juser.fz-juelich.de/record/276452