Electron ionization‐tandem mass spectrometry of glycosphingolipids. Part II. The identification of a carbohydrate sequence corresponding to a novel repetitive blood group a heptaglycosylceramide

In a previous paper, the presence in human kidney vein tissue of a novel blood group A heptaglycosylceramide based on the type‐3 carbohydrate chain GalNAcαl‐3(Fucαl‐2)Galα1‐3GalNAcαl‐3(Fucα1‐2)Galβl‐4Glcβl‐1 Ceramide, was suggested based on thin‐layer immunostaining and electron ionization mass Spectrometry. Ions corresponding lo a structure containing two deoxyhexoses, two hexosamines and three hexoses were identified, but no information was obtained from mass spectrometry concerning the carbohydrate sequence 5 . In the present paper, we report the identification of carbohydrate sequence ions corresponding to a type‐3 chain A heptaglyco‐sylceramide by electron ionization‐tandem mass spectrometry of a permethylated‐reduced glycosphingolipid mixture isolated from human kidney vein tissue. The use of a microchannel‐plate‐array detector increased the sensitivity for collision‐induced dissociation spectra by a factor of at least ten over a conventional electron multiplier.