title: Methylamidation for sialoglycomics by MALDI-MS: a facile derivatization strategy for both α2,3- and α2,6-linked sialic acids.
abstract: Neutralization of carboxylic acid is an important means to avoid sialic acid dissociation when sialylated glycans are analyzed by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). In this paper, we describe a simple and rapid method to modify the sialic acids of sialylated glycans in the presence of methylamine and (7-azabenzotriazol-1-yloxy) trispyrrolidinophosphonium hexafluorophosphate (PyAOP). After methylamidation, sialylated glycans can be analyzed by MALDI-MS without loss of the sialic acid moiety. The electrospray ionization mass spectrometry (ESI-MS) and MALDI-MS analysis of both 3'- and 6'-sialyllactose derivatives indicated that the quantitative conversion of sialic acids was achieved, regardless of their linkage types. This derivatization strategy was further validated with the N-glycans released from three standard glycoproteins (fetuin, human acid glycoprotein, and bovine acid glycoprotein) containing different types of complex glycans. Most importantly, this derivatization method enabled the successful characterization of N-glycans of sera from different species (human, mouse, and rat) by MALDI-MS. Because of the mild reaction conditions, the modification in sialic acid residues can be retained. This improvement makes it possible to detect sialylated glycans containing O-acetylated sialic acid moieties using MALDI-MS in positive-ion mode.
authors.affiliation: Britton Chance Center for Biomedical Photonics at Wuhan National Laboratory for Optoelectronics, Hubei Bioinformatics and Molecular Imaging Key Laboratory, Department of Systems Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Hongyu
authors.initials: H
authors.lastname: Qiu
authors.forename: Rhonda Kuo
authors.initials: RK
authors.lastname: Lee
authors.forename: Wangxue
authors.initials: W
authors.lastname: Chen
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
mesh_terms: D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D054794:Glycomics / Q000379:methods*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007785:Lactose / Q000031:analogs & derivatives / Q000097:blood / Q000737:chemistry; D008744:Methylamines / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009943:Organophosphorus Compounds / Q000737:chemistry; D011134:Polysaccharides / Q000097:blood / Q000737:chemistry; D051381:Rats; D012794:Sialic Acids / Q000097:blood* / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D000509:alpha-Fetoproteins / Q000737:chemistry
chemical_list: C403777:6'-sialyllactose; D006023:Glycoproteins; D008744:Methylamines; D009943:Organophosphorus Compounds; D011134:Polysaccharides; D012794:Sialic Acids; D000509:alpha-Fetoproteins; C027451:methylamine; D007785:Lactose