Multiple-stage Precursor Ion Separation and High Resolution Mass Spectrometry toward Structural Characterization of 2,3-Diacyltrehalose Family from Mycobacterium tuberculosis

Cheryl Frankfater,Loïc Lemiègre,Laurent Legentil,Robert Abramovitch,Fong-Fu Hsu,John Turk,Georgiana Purdy

doi:10.3390/separations6010004

Abstract

Mass spectrometry (MS)-based precursor ion isolation, collision-induced dissociation (CID) fragmentation, and detection using linear ion-trap multiple-stage mass spectrometry (LIT MSn) in combination with high resolution mass spectrometry (HRMS) provides a unique tool for structural characterization of complex mixture without chromatographic separation. This approach permits not only separation of various lipid families and their subfamilies, but also stereoisomers, thereby, revealing the structural details. In this report, we describe the LIT MSn approach to unveil the structures of a 2,3-diacyl trehalose (DAT) family isolated from the cell envelope of Mycobacterium tuberculosis, in which more than 30 molecular species, and each species consisting of up to six isomeric structures were found. LIT MSn performed on both [M + Na]+ and [M + HCO2]− ions of DAT yield complimentary structural information for near complete characterization of the molecules, including the location of the fatty acyl substituents on the trehalose backbone. This latter information is based on the findings of the differential losses of the two fatty acyl chains in the MS2 and MS3 spectra; while the product ion spectra from higher stage LIT MSn permit confirmation of the structural assignment.

Highlights

IntroductionTandem mass spectrometry consists of several sequential events including formation and mass selection of the precursor ions, collision induced dissociation (CID) with inert target gas for fragment ion formation, followed by mass analysis and detection of the product-ions
Tandem mass spectrometry is a powerful tool for structural analysis of unknown molecules.Tandem mass spectrometry consists of several sequential events including formation and mass selection of the precursor ions, collision induced dissociation (CID) with inert target gas for fragment ion formation, followed by mass analysis and detection of the product-ions
(X = Cl, RCO2 ; R = H, CH3, C2 H5, etc.) ions in the negative-ion mode when subjected to electrospray ionization (ESI) in the presence of Alk+ and X−

Summary

Introduction

Tandem mass spectrometry consists of several sequential events including formation and mass selection of the precursor ions, collision induced dissociation (CID) with inert target gas for fragment ion formation, followed by mass analysis and detection of the product-ions. Linear ion trap multiple stage tandem mass spectrometry (LIT MSn ) permits the repeat of the precursor ion selection-CID-product-ion analysis process, and up to 10 cycles can be performed using modern commercial LIT mass spectrometers such as Thermo LTQ Orbitrap. This instrument is featured with an extreme high resolving power and up to a million resolution (at m/z 200) can be reached [2]

Methods

Results

Conclusion