Abstract Title

Discovery and Structural Elucidation of Novel Microcystins Using MS and MSn with Python Code

Start Date

23-5-2022 5:45 PM

End Date

23-5-2022 7:00 PM

Abstract

Microcystins (MCs) are cyclic heptapeptide hepatotoxins with a vast structural diversity (>300 congeners). However, many more congeners are theoretically possible, and a workflow was developed for putative identification of novel MCs using liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS) and MSn with Python code. Water samples collected from Lake Erie were sonicated and filtered, and solid-phase extraction was performed. A portion of the water sample was reacted with mercaptoethanol using the method developed by Miles et al. for structural elucidation. Extracted MCs were analyzed using UHPLC coupled to an Orbitrap Fusion instrument for HRMS. Collision-induced dissociation (CID) and higher-energy CID (HCD) were used for MSn analyses. A total of 33 MCs were found in lake water samples, including two unknown MCs. Two Python codes were developed to elucidate the structures of MCs. Code 1 was written to generate a list of masses of theoretically possible MC congeners. Code 2 was written to compare the experimentally obtained masses of MC fragment ions to the theoretical fragment masses. Using Codes 1 and 2, the two unknown MCs with m/z values of 526.7980 (z=+2) and 1025.5302 (z=+1) were putatively identified as MC-HarR and MC-E(OMe)R, respectively.

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May 23rd, 5:45 PM May 23rd, 7:00 PM

Discovery and Structural Elucidation of Novel Microcystins Using MS and MSn with Python Code

Microcystins (MCs) are cyclic heptapeptide hepatotoxins with a vast structural diversity (>300 congeners). However, many more congeners are theoretically possible, and a workflow was developed for putative identification of novel MCs using liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS) and MSn with Python code. Water samples collected from Lake Erie were sonicated and filtered, and solid-phase extraction was performed. A portion of the water sample was reacted with mercaptoethanol using the method developed by Miles et al. for structural elucidation. Extracted MCs were analyzed using UHPLC coupled to an Orbitrap Fusion instrument for HRMS. Collision-induced dissociation (CID) and higher-energy CID (HCD) were used for MSn analyses. A total of 33 MCs were found in lake water samples, including two unknown MCs. Two Python codes were developed to elucidate the structures of MCs. Code 1 was written to generate a list of masses of theoretically possible MC congeners. Code 2 was written to compare the experimentally obtained masses of MC fragment ions to the theoretical fragment masses. Using Codes 1 and 2, the two unknown MCs with m/z values of 526.7980 (z=+2) and 1025.5302 (z=+1) were putatively identified as MC-HarR and MC-E(OMe)R, respectively.