The structures of exo-oligosaccharides produced by a symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum bv. viciae VF39 were determined using the methods of mass spectrometry and HCD fragmentation of ions. Exo-oligosaccharides were shown to be monomers, dimers and trimers of an octasaccharide repeating unit of the high-molecular-weight acidic exopolysaccharide. The major fraction was represented by octasaccharide monomers with two glucuronic acid residues at the reducing end. Heptasaccharides corresponding to an octasaccharide unit without GlcA-c or Glc-b residues in the main chain were also found in the culture liquid. Heterogeneity of exo-oligosaccharides according to the content of O-acetyl and hydroxybutanoyl substituents was revealed.

中文翻译：

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根瘤菌Rhizobium leguminosarum bv. 酸性外寡糖的质谱分析。豌豆VF39

由共生固氮细菌根瘤菌产生的外切寡糖的结构。viciae VF39 使用质谱法和 HCD 离子碎裂法测定。外切寡糖被证明是高分子量酸性外多糖的八糖重复单元的单体、二聚体和三聚体。主要部分由在还原端具有两个葡糖醛酸残基的八糖单体表示。在培养液中也发现了对应于主链中没有 GlcA-c 或 Glc-b 残基的八糖单元的七糖。根据 O-乙酰基和羟基丁酰基取代基的含量，揭示了外切寡糖的异质性。