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Studying disulfide bond rearrangement by MALDI‐RTOF PSD and MALDI‐TOF/RTOF high‐energy CID (20 keV) experiments of peptides derived from ammodytoxins
Author(s) -
Brgles Marija,
Kurtović Tihana,
Halassy Beata,
Allmaier Günter,
MarchettiDeschmann Martina
Publication year - 2011
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.1871
Subject(s) - chemistry , disulfide bond , matrix assisted laser desorption/ionization , organic chemistry , biochemistry , adsorption , desorption
Ammodytoxins (Atxs) are presynaptically neurotoxic phospholipases present in Vipera ammodytes ammodytes snake venom. Atxs show a high sequence homology and contain 14 cysteines which form seven biologically relevant disulfide bridges—connecting non‐neighboring cysteines. Formic acid cleavage was performed to confirm protein sequences by MALDI RTOF MS and resulted in 95.6% sequence coverage exhibiting only few formylations. Cysteine‐containing peptides showed adjacent signals 2 and/or 4 Da lower (according to the number of cysteines present in the peptide) than the theoretical molecular weight indicating disulfide bridge rearrangement. Post‐source decay (PSD) and high‐energy collision‐induced dissociation (CID) at 20 keV experiments showed fragmentation pattern unique for the reduced, thiol group containing and the oxidized, disulfide bridge harboring peptides. Besides typical low‐energy fragment ions observed during PSD experiments ( a ‐, b ‐, y ‐type ions), additional high‐energy fragment ions ( c ‐, x ‐, w ‐, d ‐type and internal fragments) of significant intensity were generated during fragmentation at 20 keV. In the case of charge directing N‐ and C‐termini, x ‐ and w ‐type ions were also observed during PSD. Good and up to complete sequence coverage was achieved for all studied peptides from Atxs in the case of high‐energy CID, whereas PSD lacked information particularly for larger peptides. Copyright © 2011 John Wiley & Sons, Ltd.