title: Elucidation of the fragmentation pathways of azaspiracids, using electrospray ionisation, hydrogen/deuterium exchange, and multiple-stage mass spectrometry.
abstract: Collision-induced dissociation (CID) mass spectra were generated for azaspiracids using electrospray ionisation (ESI), and hydrogen/deuterium (H/D) exchange was used to ascertain the number and type of replaceable hydrogens in the three predominant azaspiracid toxins. H/D exchange was conveniently achieved using deuterated solvents for liquid chromatography (LC). Using ion-trap mass spectrometry, multiple-stage CID experiments (MS(n)) on the protonated and fully exchanged ions were performed to decipher characteristic fragmentation pathways. The precursor and product ions from azaspiracids lost up to five water molecules from different regions during MS(n) experiments and it was possible to distinguish between the water losses from different molecular regions. These studies confirmed that the first water-loss ion in the spectra of azaspiracids resulted from dehydration at the vicinal diol at C20-C21. Five MS dissociation pathways were identified that resulted from fragmentation of the carbon skeleton of azaspiracids producing nitrogen-containing ions. Two pathways, involving cleavage of the E-ring and C27-C28, gave ions that were found in all azaspiracids. Three pathways, A-ring, C-ring and C19-C20 cleavages, were useful for distinguishing between azaspiracid analogues. The same product ions from backbone fragmentation were also observed using hybrid quadrupole time-of-flight mass spectrometry (QqTOFMS). The fragmentation of the A-ring was the most facile and was exploited in the development of LC/MS(n) methods for the analysis of azaspiracids.
authors.affiliation: PROTEOBIO, Mass Spectrometry Centre for Proteomics and Biotoxin Research, Department of Chemistry, Cork Institute of Technology, Bishopstown, Cork, Ireland.
authors.forename: Mónica
authors.initials: M
authors.lastname: Díaz Sierra
authors.forename: Ambrose
authors.initials: A
authors.lastname: Furey
authors.forename: Brett
authors.initials: B
authors.lastname: Hamilton
authors.forename: Mary
authors.initials: M
authors.lastname: Lehane
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: James
mesh_terms: D000818:Animals; D049872:Bivalvia; D041961:Deuterium Exchange Measurement; D007494:Ireland; D008387:Marine Toxins / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013141:Spiro Compounds / Q000737:chemistry* / Q000378:metabolism*; D000095702:Polyether Toxins
chemical_list: D008387:Marine Toxins; D013141:Spiro Compounds; C406592:azaspiracid; D000095702:Polyether Toxins