两性多糖存在于脆弱拟杆菌（Bacteroides fragilis）、肺炎链球菌（Streptococcus pneumonia）、金黄色葡萄球菌（Staphyococcus aureus）等细菌表面，具有独特的免疫活性。两性多糖是唯一一类T-细胞依赖性多糖抗原，能激活人体免疫系统，并产生记忆细胞。为了研究和揭示其独特免疫特性的分子机理，需要结构确定的两性寡糖分子。本项目拟采用添加剂控制的α-糖苷键的构建方法和一锅法合成策略，实现从脆弱拟杆菌提取得到的两性多糖PS A1和PS A2的全合成研究，并进行更为深入的3D结构分析、生物活性测试和在疫苗开发中的应用研究。

Zwitterionic polysaccharides (ZPSs) were found on the surface of Bacteroides fragilis, Streptococcus pneumoniae and Staphyococcus aureus and they exhibit unique immunomodulatory properties. ZPSs are the only known carbohydrate antigens to induce an immune response and produce memory cells by a T cell-dependent pathway. To understand the mechanism of their immunomodulatory activity, well-defined oligosaccharides of ZPSs are needed. So we would like to synthesize PS A1 and PS A2 zwitterionic oligosaccharides isolated from Bacteroides fragilis by use of new α-glycosidic bond formation method and one-pot synthesis method. We also plan to do 3D structural studies (Molecular Modeling, NMR and CD), biological evaluation and application in vaccine development.