Seven new microcystin variants discovered from a native Microcystis aeruginosa strain - Unambiguous assignment of product ions by tandem mass spectrometry

YULIN QI; LORENA ROSSO; DANIELA SEDAN; LEDA GIANNUZZI; DARÍO ANDRINOLO; DIETRICH A. VOLMER

RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM.

JOHN WILEY & SONS LTD

Lugar: Londres; Año: 2015 vol. 29 p. 220 - 224

0951-4198

RATIONALE: High-resolution mass spectrometry was applied to the study of a Microcystis aeruginosa strain previously reported as a [D-Leu1]MC-LR producer. Detailed analysis revealed new microcystin (MC) variants produced from the strain, and seven of these were previously unreported variants. This work shows the importance of mass accuracy forthe identification of unknown MCs.METHODS: The M. aeruginosa strain was isolated from a bloom sample collected from Argentina and acclimated to lab conditions. The MC variants in the strain were separated by UV/Vis detection-guided high-performance liquid chromatography, and their structures were unambiguous determined by tandem mass spectrometry (MS/MS).RESULTS: A simple strategywas developed for quickly locating the low-abundanceMC precursors fromcomplex samples. MS/MS anlysis revealed ten MC variants produced from the strain, of which seven have never been reported before.CONCLUSIONS: This work shows the interference of isobarics and isomers in the study of unknown MCs, and,therefore, high mass accuracy is important to avoid false assignments. Moreover, the peak list provided here (30-50fragments unambiguously assigned for ten MCs) can be used as a reference for the discovery of MCs from environmental samples.