Document Detail


Tandem mass spectrometry of kahalalides: identification of two new cyclic depsipeptides, kahalalide R and S from Elysia grandifolia.
MedLine Citation:
PMID:  17149796     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Spectra obtained using electrospray ionization mass spectrometry (ESI-MS) of the mollusk Elysia grandifolia showed a cluster of molecular ion peaks centered at a molecular mass of 1478 Da (kahalalide F, an anticancer agent). Two new molecules, kahalalide R (m/z 1464) and S (m/z 1492) were characterized using tandem mass spectrometry. The mass differences of 14 Da suggest that they are homologous molecules. In addition, previously identified kahalalide D and kahalalide G are also reported. However, the ESI-MS of the mollusk's algal diet Bryopsis plumosa showed the presence of only kahalalide F. The amino acid sequences of kahalalide R and S are proposed using collision-induced dissociation (CID) experiments of singly and doubly charged molecular ions and by comparison with the amino acid sequence of kahalalide F. The pathway is presented for the loss of amino acid residues in kahalalide F. It is observed that there is sequential loss of amino acids in the linear peptide chain, but in the cyclic part the ring opens at the amide bond rather than at the lactone linkage, and the loss of amino acid residues is not sequential. The CID experiment of the alkali-metal-cationized molecular ions shows that the sodium and potassium ions coordinate to the amide nitrogen/oxygen in the linear peptide chain of the molecule and not to the lactone oxygen of the lactone. In the case of kahalalide D, CID of the protonated peptide opens the depsipeptide ring to form a linear peptide with acylium ion, and fragment ion signals indicate losses of amino acids in sequential order. In this study, tandem mass spectrometry has provided the detailed information required to fully characterize the new peptides.
Authors:
Supriya Tilvi; C G Naik
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of mass spectrometry : JMS     Volume:  42     ISSN:  1076-5174     ISO Abbreviation:  J Mass Spectrom     Publication Date:  2007 Jan 
Date Detail:
Created Date:  2007-01-08     Completed Date:  2007-03-16     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9504818     Medline TA:  J Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  70-80     Citation Subset:  IM    
Copyright Information:
Copyright 2006 John Wiley & Sons, Ltd.
Affiliation:
National Institute of Oceanography, Dona Paula, Goa, India. supriyatilvi@rediffmail.com
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MeSH Terms
Descriptor/Qualifier:
Algae, Green / chemistry
Animals
Depsipeptides / chemistry*
Mollusca / chemistry*
Spectrometry, Mass, Electrospray Ionization
Tandem Mass Spectrometry
Chemical
Reg. No./Substance:
0/Depsipeptides; 0/kahalalide R; 0/kahalalide S; 149204-42-2/kahalalide F

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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