Conformation and Dynamics of Complex Polysaccarides

细胞表面的寡糖和多糖具有复杂的结构，编码控制细胞相互作用的信息。信息通过与蛋白质如凝集素结合来解码，凝集素通常是复杂的和多价的，并且还可能涉及蛋白质和碳水化合物结合位点之间的协同相互作用。 溶液的构象和动力学的寡糖配体，这可能有显着的影响，结合的自由能，是知之甚少，将在本项目中研究的物理方法，包括计算分子建模和NMR光谱。 复杂的寡糖和多糖的灵活性提出的模型将是有用的蛋白质-碳水化合物结合平衡的解释，并将作为高分子量多糖的动态特性的解释的基础。在复杂的支链寡糖中，连接相对刚性的吡喃糖苷椅的糖苷键具有高度变化的立体化学，其中一些键相对刚性，而另一些键高度柔性。 本研究以刘易斯型和血型寡糖为例，从草绿色链球菌、S. mitis和S. oralis将是更灵活的寡糖的模型。 除了传统的核Overhauser方法，NMR实验，涉及异构标量耦合的糖苷键将在天然丰度样品和稳定同位素的生物合成掺入制备的样品进行研究。最近推出的方法的残余偶极偶联低聚糖部分取向的稀液晶溶液能够提供丰富的和非常精确的实验信息的刚性低聚糖表位的构象和新的方法来处理灵活的低聚糖将被使用，这将导致大大改善模型的构象和动力学的铰链，加入更多的刚性域。 实验结果将用计算机分子模拟计算进行解释，包括分子动力学模拟和蒙特卡罗方法。本项目将支持研究生和本科生的结构生物化学培训，他们将学习现代核磁共振实验和计算机分子模拟方法，沿着复杂碳水化合物的分析和物理生物化学方面。 PI的部门有一个特别强大的传统，在培训代表性不足的少数民族学生，无论是在研究生和本科生水平。

The oligosaccharides and polysaccharides of the cell surface have complex structures encoding information which controls cellular interactions. The information is decoded by binding to proteins such as lectins which is often complex and multivalent and may also involve cooperative interactions between protein and carbohydrate binding sites. The solution conformation and the dynamics of the oligosaccharide ligands, which can have a significant influence on the free energy of binding, is poorly understood and will be studied in this project by physical methods including computational molecular modeling and NMR spectroscopy. The model proposed for flexibility in complex oligosaccharides and polysaccharides will be useful for interpretation of protein-carbohydrate binding equilibria and will serve as a basis for interpretation of the dynamic properties of high molecular weight polysaccharides. The glycosidic linkages joining the comparatively rigid pyranoside chairs in complex, branched oligosaccharides have highly varied stereochemistry with some linkages being relatively rigid and others highly flexible. In this research, examples of relatively rigid oligosaccharides will be selected from the Lewis and blood group oligosaccharides while oligosaccharides and polysaccharides isolated from the cell walls of the viridans streptococci, S. mitis and S. oralis will be models for more flexible oligosaccharides. In addition to traditional nuclear Overhauser methods, NMR experiments involving heteronuclear scalar coupling across the glycosidic linkages will be studied both in natural abundance samples and in samples prepared with biosynthetic incorporation of stable isotopes. The recently introduced method of residual dipolar coupling of oligosaccharides partially oriented in dilute liquid crystal solutions is capable of giving abundant and very precise experimental information on the conformation of rigid oligosaccharide epitopes and new methods for treating flexible oligosaccharides will be used which will lead to greatly improved models for conformation and dynamics of the hinges which join more rigid domains. The experimental results will be interpreted with computer molecular modeling calculations including molecular dynamics simulations and Monte Carlo methods.This project will support training in structural biochemistry for graduate and undergraduate students who will learn modern nuclear magnetic resonance experiments and computer molecular modeling methods along with aspects of the analytical and physical biochemistry of complex carbohydrates. The PI's department has an especially strong tradition in training of under represented minority students, both at the graduate and undergraduate level.