title: Label-free absolute quantitation of oligosaccharides using multiple reaction monitoring.
abstract: An absolute quantitation method for measuring free human milk oligosaccharides (HMOs) in milk samples was developed using multiple reaction monitoring (MRM). To obtain the best sensitivity, the instrument conditions were optimized to reduce the source and postsource fragmentation prior to the quadrupole transmission. Fragmentation spectra of HMOs using collision-induced dissociation were studied to obtain the best characteristic fragments. At least two MRM transitions were used to quantify and identify each structure in the same run. The fragment ions corresponded to the production of singly charged mono-, di-, and trisaccharide fragments. The sensitivity and accuracy of the quantitation using MRM were determined, with the detection limit in the femtomole level and the calibration range spanning over 5 orders of magnitude. Seven commercial HMO standards were used to create calibration curves and were used to determine a universal response for all HMOs. The universal response factor was used to estimate absolute amounts of other structures and the total oligosaccharide content in milk. The quantitation method was applied to 20 human milk samples to determine the variations in HMO concentrations from women classified as secretors and nonsecretors, a phenotype that can be identified by the concentration of 2'-fucosylation in their milk.
authors: Department of Chemistry, University of California , One Shields Avenue, Davis, California 95616, United States.
authors: Qiuting
authors: Q
authors: Hong
authors: L Renee
authors: LR
authors: Ruhaak
authors: Sarah M
authors: SM
authors: Totten
authors: Jennifer T
authors: JT
authors: Smilowitz
authors: J Bruce
authors: JB
authors: German
authors: Carlito B
authors: CB
authors: Lebrilla
mesh_terms: D057230:Limit of Detection; D013058:Mass Spectrometry; D009844:Oligosaccharides / Q000032:analysis*
chemical_list: D009844:Oligosaccharides