摘要目的：分析B群脑膜炎球菌荚膜多糖的分子大小分布和结构特性，为B群多糖类疫苗的研制提供理论依据。方法 Sepharose CL-4B柱层析分析B群荚膜多糖分子大小分布；基质辅助激光解吸附电离-飞行时间质谱（ matrix assisted laser desorption ionization time of flight mass spectrometry ，MALDI-TOF-MS）分析B群荚膜多糖重复单位相对分子质量；以C群荚膜多糖及唾液酸为对照，用核磁共振（ Nu-clear magnetic resonance ， NMR）法分析B群荚膜多糖的结构，通过各特征质子的化学位移分析其结构特征。结果15株B群菌株的粗制荚膜多糖分配系数K D值在0．60～0．76之间；重复单位相对分子质量为284，与其理论重复单位相对分子质量284一致。 B群荚膜多糖是由唾液酸为重复单位组成的，为2→8键连接，其中不含O-乙酰基修饰。结论 B群脑膜炎球菌荚膜多糖相对分子质量较小，这可能是引起其弱免疫原性的重要因素。通过NMR法能够实现对B群荚膜多糖结构的快速、准确分析。

abstractsObjective To investigate the molecular size distribution and the structure of group B me-ningococcal capsular polysaccharides for the development of vaccines .Methods The molecular size distribution of group B meningococcal capsular polysaccharides was analyzed by chromatography on a Sepharose CL -4B col-umn.The molecular weight of repeat units were measured by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS).The structural characteristics of group B meningococcal capsular polysaccharides were analyzed by nuclear magnetic resonance ( NMR) based on the chemical shift of all charac-teristic protons by using group C meningococcal capsular polysaccharides and sialic acid as the controls .Results The KD value of group B meningococcal capsular polysaccharides extracted from 15 strains were ranged from 0.60 to 0.76.The molecular weight of repeat units was 284, which was identical to the theoretical value .The group B meningococcal capsular polysaccharides were 2→8 linked homopolymers of sialic acid lacking O-acetyl groups.Conclusion The group B meningococcal capsular polysaccharides had lower molecular weights , which might result in their poor immunogenicity .The structure of group B meningococcal capsular polysaccharides could be quickly and accurately analyzed by NMR technology .