title: Derivatization for stabilizing sialic acids in MALDI-MS.
abstract: While matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is useful in oligosaccharide analysis, the sialic acid, or N-acetylneuraminic acid (NANA), moiety of an oligosaccharide is liable to dissociation in- or postsource during mass measurement. In this study, we tried to stabilize the moiety by amidation, as in the case of peptides (Sekiya, S.; Wada, Y. Tanaka, K. Anal. Chem. 2004, 76, 5894-5902), and found 4-(4,6-dimethoxy-1,3,5-triazin-2yl)-4-methylmorpholinium chloride to be a desirable condensing agent. Amidation stabilized the glycosidic bond with NANA and suppressed its preferential cleavage by in-source decay, postsource decay, or collision-induced dissociation. In addition, the suppressed dissociation considerably improved the yield of the B/Y type ions for structural analysis by MS/MS. These results demonstrate that amidation is an effective derivatization to reinforce the structural analysis of sialylated oligosaccharides by MALDI-MS. In addition, amidation with (15)N-labeled ammonium chloride decreases the mass shift from the acid to amide form to just 0.013, reducing the complexity of mass spectral interpretation and database searching.
authors.affiliation: Koichi Tanaka Mass Spectrometry Research Laboratory, Shimadzu Corporation, Nakagyo-ku, Kyoto 604-8511, Japan. sekiya@shimadzu.co.jp
authors.forename: Sadanori
authors.initials: S
authors.lastname: Sekiya
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Wada
authors.forename: Koichi
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000586:Amination; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D009844:Oligosaccharides / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D012794:Sialic Acids / Q000032:analysis* / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014168:Transferrin / Q000737:chemistry
chemical_list: D009844:Oligosaccharides; D011134:Polysaccharides; D012794:Sialic Acids; D014168:Transferrin