Characterization of phosphatidylethanolamine as a lithiated adduct by triple quadrupole tandem mass spectrometry with electrospray ionization

Structural characterization of the glycerophosphoethanolamine (GPE) molecule as a lithiated adduct ion by collisionally activated dissociation (CAD) tandem mass spectrometry with electrospray ionization is described. Abundant fragment ions reflecting polar head group and fatty acid constituents were observed in the product ion spectrum of GPE, which permits an unambiguous structural determination, including the regiospecificity of fatty acyl substituents. The pathways leading to the formation of fragment ions are proposed. The suggested mechanisms are supported by the tandem mass spectra of various deuterated analogs and source CAD of GPE followed by CAD tandem mass spectrometry. Identification of GPE molecular species and specific GPE subclasses in a biological mixture by tandem mass spectrometry with various constant neutral loss scannings is also described.