Received for review June 6, 2006. Revised manuscript received July 28, 2006. Accepted August 7, 2006. This research was funded in part by the California Dairy Research Foundation (CDRF), by an NIH- funded fellowship under the Training Program in Biomolecular Technology (Grant T32GM08799) at the University of California, Davis (R.E.W.), by The CHARGE Study (Grant P01ES11269), and by the UC Discovery Grant.

Abstract:

Oligosaccharides in human milk represent a group of bioactive molecules that have evolved to be an abundant and diverse component of human milk, even though they have no direct nutritive value to the infant. A recent hypothesis proposes that they could be substrates for the development of the intestinal microflora and the mucosal immune system. The inability to determine the exact composition of these oligosaccharides limits research and the ability to understand their biological functions. Oligosaccharides isolated from the lipids and proteins of individual human milk samples were analyzed by a combination of techniques including microchip liquid chromatography mass spectrometry (HPLC-Chip/MS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT ICR MS). Accurate mass measurements obtained using an orthogonal time-of-flight (o-TOF) mass spectrometry provided oligosaccharide composition for approximately 200 individual molecular species. Comparison of HPLC-Chip/MS profiles from five different women revealed variations in milk oligosaccharide compositions. HPLC-Chip/MS profiling provides a method for routinely identifying milk oligosaccharides. Tandem MS in combination with exoglycosidase digestion provides unambiguous differentiation of structural isomers.

Keywords: Human milk oligosaccharides; milk glycome; HPLC-Chip/MS technology; infrared multiphoton dissociation; exoglycosidases; matrix-assisted laser desorption/ionization Fourier transform mass spectrometry

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