Structural determination of sphingomyelin by tandem mass spectrometry withelectrospray ionization

Alkaline metal adduct ions of sphingomyelin were formed by electrospray ion ization in positive ion mode. Under low energy collisionally activated diss ociation (CAD), the product ion spectra yield abundant fragment ions repres entative of both long chain base and fatty acid which permit unequivocal de termination of the structure. Tandem spectra obtained by constant neutral l oss scanning permit identification of sphingomyelin class and specific long chain base subclass in the mixture. The fragmentation pathways under CAD w ere proposed, and were further confirmed by source CAD tandem mass spectrom etry. The total analysis of sphingomyelin mixtures from bovine brain, bovin e erythrocytes, and chicken egg yolk is also presented. (C) 2000 American S ociety for Mass Spectrometry.