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Identification of alpha- and beta-Hydroxy Acid Containing Cyclodepsipeptides in Natural Peptide Mixtures Using Negative Ion Mass Spectrometry

Thakur, Suman S and Ranganayaki, Rappal S and Gupta, Kallol and Balaram, Padmanabhan (2009) Identification of alpha- and beta-Hydroxy Acid Containing Cyclodepsipeptides in Natural Peptide Mixtures Using Negative Ion Mass Spectrometry. In: Journal of the American Society for Mass Spectrometry, 20 (12). pp. 2221-2228.

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Abstract

Natural peptide libraries often contain cyclodepsipeptides containing alpha or beta hydroxy residues. Extracts of fungal hyphae of Isaria yield a microheterogenous cyclodepsipeptide mixture in which two classes of molecules can be identified by mass spectral fragmentation of negative ions. In the case of isaridins, which contain an alpha-hydroxy residue and a beta-amino acid residue, a characteristic product ion corresponding to a neutral loss of 72 Da is obtained. hi addition, neutral loss of water followed by a 72 Da loss is also observed. Two distinct modes of fragmentation rationalize the observed product ion distribution. The neutral loss of 72 Da has also been obtained for a roseotoxin component, which is also an alpha-hydroxy residue containing cyclodepsipeptide. In the case of isariins, which contain a beta-hydroxy acid residue, ring opening and subsequent loss of the terminal residue as an unsaturated ketene fragment, rationalizes the observed product ion formation. Fragmentation of negative ions provide characteristic neutral losses, which are diagnostic of the presence of alpha-hydroxy or beta-hydroxy residues.

Item Type: Journal Article
Additional Information: copyright of this article belongs to Elsevier Science.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 09 Jan 2010 11:02
Last Modified: 19 Sep 2010 05:54
URI: http://eprints.iisc.ernet.in/id/eprint/25306

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