Comparative Studies of Sialyloligosaccharides in Human Milk During Different Phases of Lactation Using Isotope Labeling and Electrospray Ion Trap Mass Spectrometry
Date Issued
2012
Date
2012
Author(s)
Liu, Hsi-Yen
Abstract
Sialyloligosaccharides of human milk are significant in anti-adhesion of pathogenic organism and the precursors for biosynthesis of brain for newborn infants. Accurate quantitative analysis of sialyloligosaccharides in human milk during different lactation phases is needed to investigate the physiological role of sialyloligosaccharides for newborn infants.
Methylamidation provides a simple and rapid labeling method for modifying the sialic acids of sialyloligosaccharides. Using d0/d3-methylamine stable isotopic labeling, methylamidation has been applied to relative quantitative analysis of sialyloligosaccharides by mass spectrometry. Applications of this method on 3’-sialyllactose and N-linked glycans released from transferrin demonstrates a 5-fold relative quantitative dynamic range, a satisfying linear dependency and slope between the molar ratios and the calculated intensity ratios of the d0/d3-derivatives. Comparative quantitative analysis for sialyloligosaccharides isolated from three different phases of lactation has been successfully performed by this technique. During lactation, the concentrations of sialyllactose, sialyllactose-N-tetraose, monofucosyl,monosialyllacto-N-tetraose and disialyl-lacto-N-tetraose are first decreased then increased slightly. The concentrations of sialyllacto-N-hexaose, monofucosyl,monosialyllacto-N-hexaose and difucosyl,monosialyllacto-N-hexaose are first decreased then increased by 1.5 ~ 2.3 folds.
In addition, by applying the proper collision energy, 3’-sialyllactose and 6’-sialyllactose can be differentiated by diagnostic peaks. Relative abundance analysis of each isomer can be achieved by comparing the intensities of the diagnostic peaks. We found that during lactation, the quantity of 3’-sialyllactose decreases by 18 ~ 38%, while that of 6’-sialyllactose remains the same level.
Subjects
Mass spectrometry
Stable isotopic labeling
Methylamidation
Human milk
Sialyloligosaccharide
Isomer
Type
thesis
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