Advertisement

Electrospray ionization multiple-stage linear ion-trap mass spectrometry for structural elucidation of triacylglycerols: Assignment of fatty acyl groups on the glycerol backbone and location of double bonds

  • Fong-Fu Hsu
  • John Turk
Article

Abstract

Linear ion-trap multiple-stage mass spectrometric approach (MS n ) towards nearly complete structural elucidation of triacylglycerol (TAG) including (1) assignment the fatty acid substituents on the glycerol backbone and (2) location of the double bond(s) on the unsaturated fatty acyl groups is reported. The characterization is established by the findings that MS2 on the [M+Li]+ ions of TAG yields more abundant ions reflecting losses of the outer fatty acid substituents either as free acids (i.e., [M+Li-R1CO2H]+ and [M+Li-R3CO2H]+ ions) or as lithium salts (i.e., [M+Li-R1CO2Li]+ and [M+Li-R3CO2Li]+ ions) than the ions reflecting the similar losses of the inner fatty acid substituent (i.e., [M+Li-R2CO2Li]+ and [M+Li-R2CO2Li]+ ions). Further dissociation (MS3) of [M+Li-R n CO2H]+ (n=1, 2, or 3) gives rise to the ion series locating the double bonds along the fatty acid chain. These ions arise from charge-remote fragmentations involving β-cleavage with γ-H shift, analogous to those seen for the unsaturated long-chain fatty acids characterized as initiated ions. Significant differences in abundances in the ion pairs reflecting the additional losses of the fatty acid moieties, respectively, were also seen in the MS3 spectra of the [M+Li-R n CO2H]+ and [M+Li-R n CO2Li]+ ions, leading to confirmation of the fatty acid substituents on the glycerol backbone. MS n on the [M+Na]+ and [M+NH4]+ adduct ions also affords location of fatty acid substituents on the glycerol backbone, but not the position of the double bond(s) along the fatty acid chain. Unique ions from internal losses of the glycerol residues were seen in the MS3 spectra of [M+Alk-R n CO2H]+ (n=1, 2, 3) and of [M+Alk-R n CO2Alk]+ (Alk=Li, Na, NH4; n=1, 3). They are signature ions for glycerides and the pathways leading to their formation may involve rearrangements.

Keywords

Fatty Acyl Glycerol Backbone Fatty Acid Moiety Double Bond Position Lithium Salt 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Supplementary material

13361_2011_210400657_MOESM1_ESM.pdf (293 kb)
Supplementary material, approximately 300 KB.

References

  1. 1.
    Cheng, C.; Gross, M. L.; Pittenauer, E. Complete Structural Elucidation of Triacylglycerols by Tandem Sector Mass Spectrometry. Anal. Chem. 1998, 70, 4417–4426.CrossRefGoogle Scholar
  2. 2.
    Duffin, K. L.; Henion, J. D.; Shieh, J. J. Electrospray and Tandem Mass Spectrometric Characterization of Acylglycerol Mixtures That Are Dissolved in Nonpolar Solvents. Anal. Chem. 1991, 63, 1781–1788.CrossRefGoogle Scholar
  3. 3.
    Pittenauer, E.; Allmaier, G. The Renaissance of High-Energy CID for Structural Elucidation of Complex Lipids: MALDI-TOF/RTOF-MS of Alkali Cationized Triacylglycerols. J. Am. Soc. Mass Spectrom. 2009, 20, 1037–1047.CrossRefGoogle Scholar
  4. 4.
    Hsu, F.-F.; Turk, J. Structural Characterization of Triacylglycerols as Lithiated Adducts by Electrospray Ionization Mass Spectrometry Using Low-Energy Collisionally Activated Dissociation on a Triple Stage Quadrupole Instrument. J. Am. Soc. Mass Spectrom. 1999, 10, 587–599.CrossRefGoogle Scholar
  5. 5.
    Lin, J.-T.; Arcinas, A. Regiospecific Analysis of Diricinoleoylglycerols in Castor (Ricinus communis L.) Oil by Electrospray Ionization-Mass Spectrometry. J. Agric. Food Chem. 2007, 55, 2209–2216.CrossRefGoogle Scholar
  6. 6.
    Thomas, M. C.; Mitchell, T. W.; Blanksby, S. J. Ozonolysis of Phospholipid Double Bonds During Electrospray Ionization: A New Tool for Structure Determination. J. Am. Chem. Soc. 2006, 128, 58–59.CrossRefGoogle Scholar
  7. 7.
    Thomas, M. C.; Mitchell, T. W.; Harman, D. G.; Deeley, J. M.; Murphy, R. C.; Blanksby, S. J. Elucidation of Double Bond Position in Unsaturated Lipids by Ozone Electrospray Ionization Mass Spectrometry. Anal. Chem. 2007, 79, 5013–5022.CrossRefGoogle Scholar
  8. 8.
    Thomas, M. C.; Mitchell, T. W.; Harman, D. G.; Deeley, J. M.; Nealon, J. R.; Blanksby, S. J. Ozone-Induced Dissociation: Elucidation of Double Bond Position within Mass-Selected Lipid Ions. Anal. Chem. 2008, 80, 303–311.CrossRefGoogle Scholar
  9. 9.
    Hsu, F.-F.; Turk, J. Electrospray Ionization/Tandem Quadrupole Mass Spectrometric Studies on Phosphatidylcholines: The Fragmentation Processes. J. Am. Soc. Mass Spectrom. 2003, 14, 352–363.CrossRefGoogle Scholar
  10. 10.
    Hsu, F.-F.; Turk, J. Electrospray Ionization with Low-Energy Collisionally Activated Dissociation Tandem Mass Spectrometry of Glycerophospholipids: Mechanisms of Fragmentation and Structural Characterization. J. Chromatogr. B 2009, 877, 2673–2695.CrossRefGoogle Scholar
  11. 11.
    Hsu, F.-F.; Turk, J. Structural Characterization of Unsaturated Glycerophospholipids by Multiple-Stage Linear Ion-Trap Mass Spectrometry with Electrospray Ionization. J. Am. Soc. Mass Spectrom. 2008, 19, 1681–1691.CrossRefGoogle Scholar
  12. 12.
    Hsu, F.-F.; Turk, J. Elucidation of the Double Bond Position of Long-Chain Unsaturated Fatty Acids by Multiple-Stage Linear Ion-Trap Mass Spectrometry with Electrospray Ionization. J. Am. Soc. Mass Spectrom. 2008, 19, 1673–1680.CrossRefGoogle Scholar
  13. 13.
    Hsu, F.-F.; Turk, J. Studies on Phosphatidylserine by Tandem Quadrupole and Multiple Stage Quadrupole Ion-Trap Mass Spectrometry with Electrospray Ionization: Structural Characterization and the Fragmentation Processes. J. Am. Soc. Mass Spectrom. 2005, 16, 1510–1522.CrossRefGoogle Scholar
  14. 14.
    Hsu, F.-F.; Turk, J.; Owens, R. M.; Rhoades, E. R.; Russell, D. G. Structural Characterization of Phosphatidyl-Myo-Inositol Mannosides from Mycobacterium bovis Bacillus Calmette Guerin by Multiple-Stage Quadrupole Ion-Trap Mass Spectrometry with Electrospray Ionization. I. PIMs and Lyso-PIMs. J. Am. Soc. Mass Spectrom 2007, 18, 466–478.CrossRefGoogle Scholar
  15. 15.
    Hsu, F.-F.; Turk, J.; Owens, R. M.; Rhoades, E. R.; Russell, D. G. Structural Characterization of Phosphatidyl-Myo-Inositol Mannosides from Mycobacterium bovis Bacillus Calmette Guerin by Multiple-Stage Quadrupole Ion-Trap Mass Spectrometry with Electrospray Ionization. II. Monoacyl- and Diacyl-PIMs. J. Am. Soc. Mass Spectrom. 2007, 18, 479–492.CrossRefGoogle Scholar
  16. 16.
    Adams, J.; Gross, M. L. Energy Requirement for Remote Charge Site Ion Decomposition and Structural Information from Collisional Activation of Alkali Metal Cationized Fatty Alcohols. J. Am. Chem. Soc. 1986, 108, 6915–6921.CrossRefGoogle Scholar
  17. 17.
    McAnoy, A. M.; Wu, C. C.; Murphy, R. C. Direct Qualitative Analysis of Triacylglycerols by Electrospray Mass Spectrometry Using a Linear Ion Trap. J. Am. Soc. Mass Spectrom. 2005, 16, 1498–1509.CrossRefGoogle Scholar
  18. 18.
    Momchilova, S.; Tsuji, K.; Itabashi, Y.; Nikolova-Damyanova, B.; Kuksis, A. Resolution of Triacylglycerol Positional Isomers by Reversed-Phase High-Performance Liquid Chromatography. J. Sep. Sci. 2004, 27, 1033–1036.CrossRefGoogle Scholar
  19. 19.
    Ikeda, K.; Oike, Y.; Shimizu, T.; Taguchi, R. Global Analysis of Triacylglycerols Including Oxidized Molecular Species by Reverse-Phase High Resolution LC/ESI-QTOF MS/MS. J. Chromatogr. B 2009, 877, 2639–2647.CrossRefGoogle Scholar

Copyright information

© American Society for Mass Spectrometry 2010

Authors and Affiliations

  1. 1.Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid research, Department of Internal MedicineWashington University School of MedicineSt. LouisUSA

Personalised recommendations