Positive-ion ESI mass spectrometry of regioisomeric nonreducing oligosaccharide fatty acid monoesters: in-source fragmentation of sodium adducts.
Structural characterization and differentiation of a novel group of regioisomeric monolaurate esters of the nonreducing trisaccharides raffinose and melezitose, and the nonreducing tetrasaccharide stachyose has been obtained using positive electrospray ionization (ESI) mass spectrometry with in-source fragmentation. The surfactant nature and high polarity of these compounds make them appropriate analytes for being studied by conventional ESI-MS. The position of the acyl chain in each particular regioisomer has been used as a reporter group that allows unambiguous rationalization of the fragmentation routes of the corresponding natriated molecular ions [M + Na](+). In all cases, the main fragment ions were produced through cleavage of the glycosidic bond involving two anomeric carbons, the C-1' and C-2'' of the alpha-D-Glcp-(1-2)-beta-D-Fruf bond, and it was observed that sodium cation retention occurred on the heavier mass fragment of the two formed fragments, (e.g. di- or trisaccharide type vs monosaccharide type). Our results may help to better understand the fragmentation behavior of nonreducing oligosaccharides (as sodium adducts) in positive ESI mass spectrometry.
Pérez-Victoria
Ignacio
I
Departamento de Química, Puleva Biotech SA, Granada, Spain. i.perez-victoria@tnw.utwente.nl
Zafra
Alberto
A
Morales
Juan Carlos
JC
D002412:Cations; D004952:Esters; D005227:Fatty Acids / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry*; D010084:Oxidation-Reduction; D012964:Sodium / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism
D002412:Cations; D004952:Esters; D005227:Fatty Acids; D009844:Oligosaccharides; D012964:Sodium