Structural elucidation of diglycosyl diacylglycerol and monoglycosyl diacylglycerol from Streptococcus pneumoniae by multiple-stage linear ion-trap mass spectrometry with electrospray ionization

Raju Venkata Veera Tatituri, Michael B. Brenner, John Turk, Fong Fu Hsu

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

The cell wall of the pathogenic bacterium Streptococcus pneumoniae contains glucopyranosyl diacylglycerol (GlcDAG) and galactoglucopyranosyldiacylglycerol (GalGlcDAG). The specific GlcDAG consisting of vaccenic acid substituent at sn-2 was recently identified as another glycolipid antigen family recognized by invariant natural killer T-cells. Here, we describe a linear ion-trap multiple-stage (MS n) mass spectrometric approach towards structural analysis of GalGlcDAG and GlcDAG. Structural information derived from MS n (n = 2, 3) on the [M + Li] + adduct ions desorbed by electrospray ionization affords identification of the fatty acid substituents, assignment of the fatty acyl groups on the glycerol backbone, as well as the location of double bond along the fatty acyl chain. The identification of the fatty acyl groups and determination of their regio-specificity were confirmed by MS n (n = 2, 3) on the [M + NH 4] + ions. We establish the structures of GalGlcDAG and GlcDAG isolated from S. pneumoniae, in which the major species consists of a 16:1- or 18:1-fatty acid substituent mainly at sn-2, and the double bond of the fatty acid is located at ω-7 (n-7). More than one isomers were found for each mass in the family. This mass spectrometric approach provides a simple method to achieve structure identification of this important lipid family that would be very difficult to define using the traditional method.

Original languageEnglish
Pages (from-to)115-123
Number of pages9
JournalJournal of Mass Spectrometry
Volume47
Issue number1
DOIs
StatePublished - Jan 2012

Keywords

  • ESI
  • diglycosyl diacylglycerol
  • glycolipids
  • ion-trap mass spectrometry
  • lithium adduct ion
  • monoglycosyl diacylglycerol
  • streptococcus pneumoniae

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