title: Thermal decomposition of beta-D-galactopyranosyl-(1-->3)-2-acetamido-2-deoxy-D-hexopyranoses under neutral conditions.
abstract: beta-d-Galactopyranosyl-(1-->3)-2-acetamido-2-deoxy-d-glucose (LNB) and beta-d-galactopyranosyl-(1-->3)-2-acetamido-2-deoxy-d-galactose (GNB) decompose rapidly upon heating into d-galactose and mono-dehydrated derivatives of the corresponding 2-acetamido-2-deoxy-d-hexoses, including 2-acetamido-2,3-dideoxy-hex-2-enofuranoses and bicyclic 2-acetamido-3,6-anhydro-2-deoxy-hexofuranoses. The decomposition is conducted under neutral conditions where glycosyl linkages are generally believed to be stable. The half-lives of LNB and GNB were 8.1min and 20min, respectively, at 90 degrees C and pH 7.5. The pH dependency of decomposition rates suggests that the instabilities are an extension of the conditions for the peeling reaction, often observed with glycans of O-linked glycoproteins under alkaline conditions. Such decomposition under the neutral conditions is commonly observed with 3-O-linked reducing aldoses.
authors.affiliation: National Food Research Institute, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Chiku
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nishimoto
authors.forename: Motomitsu
authors.initials: M
authors.lastname: Kitaoka
mesh_terms: D002240:Carbohydrate Sequence; D005690:Galactose / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D010100:Oxygen / Q000737:chemistry
chemical_list: D010100:Oxygen; D005690:Galactose