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Issue 18, 2011
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Effect of ester chemical structure and peptide bond conformation in fragmentation pathways of differently metal cationized cyclodepsipeptides

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Abstract

Fragmentation behavior of two classes of cyclodepsipeptides, isariins and isaridins, obtained from the fungus Isaria, was investigated in the presence of different metal ions using multistage tandem mass spectrometry (MSn) with collision induced dissociation (CID) and validated by NMR spectroscopy. During MSn process, both protonated and metal-cationized isariins generated product ions belonging to the identical ‘b-ion’ series, exhibiting initial backbone cleavage explicitly at the β-ester bond. Fragmentation behavior for the protonated and metal-cationized acyclic methyl ester derivative of isariins was very similar. On the contrary, isaridins during fragmentation produced ions belonging to the ‘b’ or/and the ‘y’ ion series depending on the nature of interacting metal ions, due to initial backbone cleavages at the α-ester linkage or/and at a specific amide linkage. Interestingly, independent of the nature of the interacting metal ions, the product ions formed from the acyclic methyl ester derivative of isaridins belonged only to the ‘y-type’. Complementary NMR data showed that, while all metal ions were located around the β-ester group of isariins, the metal ion interacting sites varied across the backbone for isaridins. Combined MS and NMR data suggest that the different behavior in sequence specific charge-driven fragmentation of isariins and isaridins is predetermined because of the constituent β-hydroxy acid residue in isariins and the cispeptide bond in isaridins.

Graphical abstract: Effect of ester chemical structure and peptide bond conformation in fragmentation pathways of differently metal cationized cyclodepsipeptides

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Publication details

The article was received on 13 Mar 2011, accepted on 25 May 2011 and first published on 31 May 2011


Article type: Paper
DOI: 10.1039/C1OB05392B
Citation: Org. Biomol. Chem., 2011,9, 6234-6245
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    Effect of ester chemical structure and peptide bond conformation in fragmentation pathways of differently metal cationized cyclodepsipeptides

    R. Banerjee, S. Sudarslal, R. S. Ranganayaki and S. Raghothama, Org. Biomol. Chem., 2011, 9, 6234
    DOI: 10.1039/C1OB05392B

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