Theory and Computer Simulations of Polyampholyte-Polyelectrolyte Complexes

该奖项支持理论和计算研究和教育，旨在开发含有两性聚电解质-水溶性复合物的溶液的分子水平模型。当一种蛋白质与一种具有相同净电荷的两性电解质（蛋白质）混合时，就会形成一种可溶性复合物。这种结合是以这样一种方式发生的，即蛋白质上带相反电荷的氨基酸靠近蛋白质，导致两者之间的静电吸引。在大量过量的两性聚电解质的情况下，每个双链均被两性聚电解质饱和，并且溶液是液体。 随着添加更多的淀粉，粘度稳定地增加。一旦加入足够的双链，就会形成可逆的凝胶，其中一些聚两性电解质分子充当双链之间的临时交联。该研究旨在开发分子模型，描述在广泛的聚合物和盐浓度，溶液pH值和聚合物的各种性质（如分子量和电荷分布）中形成的聚两性电解质-水溶性复合物。在稀溶液中，所得到的模型将提供详细的内部结构的聚两性电解质-反离子复合物和反离子的释放和冷凝的复合物的形成的影响。将在半稀溶液中研究络合物间缔合和可逆凝胶化的形成。这将允许预测聚合物构象和溶液性质，如粘度、扩散系数和弛豫时间。 理论模型的假设将通过计算机模拟进行检验。将渗透系数、扩散系数、线性粘弹性和稳态剪切粘度的计算结果与实验结果进行了比较。 将开发的两性聚电解质-水溶性复合物的分子模型可能在生物医学领域以及利用带电大分子作为流变改性剂的领域中具有深远的影响。例如，蛋白质-脂质复合物控制滑液的流变学和润滑性质。蛋白质-淀粉复合物的实际工业用途是使用聚电解质来提高蛋白质溶液的粘度，用于涂布照相胶片和纸。 在这两种情况下，蛋白质和蛋白质之间的关联直接控制复合物的流变学。 拟议的项目非常适合培养本科生和研究生在现代分析和数值技术和指导集成到拟议的研究的各个方面。 研究生将与本科物理，化学或化学工程专业的学生一起工作，他们将通过独立研究或通过本科生（REU）课程的研究经验参与其中。建议的研究结果将被纳入高分子物理，高分子物理化学的课程序列，以及新的专题课程，带电大分子。该奖项支持理论和计算研究和教育，旨在开发含有带电聚合物，聚两性电解质-水溶性复合物的溶液的分子水平模型。当一种两性电解质（如聚丙烯酸）与一种具有相同净电荷的两性电解质（如蛋白质）混合时，就会形成一种可溶性复合物。蛋白质上的带相反电荷的氨基酸被结合在靠近蛋白质的地方，导致两者之间的静电吸引。当两性聚电解质大量过量时，溶液为液体。 随着添加更多的淀粉，粘度稳定地增加。一旦加入足够的水，就会形成可逆的凝胶。该研究旨在开发分子模型，描述在广泛的条件下形成的聚两性电解质-双金属络合物。在稀溶液中，所得到的模型将能够预测聚合物的构象，以及各种溶液性质，如粘度，扩散系数和弛豫时间。 理论模型的假设将通过计算机模拟进行测试，并将各种属性的预测与实验进行比较。 将开发的两性聚电解质-水溶性复合物的分子模型可能在生物医学领域以及利用带电大分子作为流变改性剂的领域中具有深远的影响。例如，蛋白质-脂质复合物控制滑液的流变学和润滑性质。蛋白质-淀粉复合物的实际工业用途是使用聚电解质来提高蛋白质溶液的粘度，用于涂布照相胶片和纸。 在这两种情况下，蛋白质和蛋白质之间的关联直接控制复合物的流变学。 拟议的项目非常适合培养本科生和研究生在现代分析和数值技术和指导集成到拟议的研究的各个方面。 研究生将与本科物理，化学或化学工程专业的学生一起工作，他们将通过独立研究或通过本科生（REU）课程的研究经验参与其中。建议的研究结果将被纳入高分子物理，高分子物理化学的课程序列，以及新的专题课程，带电大分子。***

This award supports theoretical and computational research and education with an aim to develop molecular level models of solutions containing polyampholyte-polyelectrolyte complexes. When a polyelectrolyte is mixed with a polyampholyte (protein) of the same net charge, a soluble complex is formed. The binding occurs in such a way that the oppositely charged amino acids on the protein are close to the polyelectrolyte, causing an electrostatic attraction between the two. With a large excess of polyampholyte, each polyelectrolyte chain is saturated with polyampholytes and the solution is a liquid. As more polyelectrolyte is added, the viscosity steadily increases. Once, enough polyelectrolyte is added, a reversible gel is formed with some polyampholyte molecules acting as temporary crosslinks between polyelectrolyte chains. The research aims to develop molecular models describing the formation of polyampholyte-polyelectrolyte complexes in a wide range of polymer and salt concentrations, solution pH and various properties of polymers like their molecular weight and charge distribution. In dilute solutions the resulting model will provide details of the internal structure of polyampholyte-polyelectrolyte complexes and of the effects of counterion release and condensation on the complex formation. The formation of intercomplex associations and reversible gelation will be studied in semidilute solutions. This will allow prediction of polymer conformations, and solution properties such as viscosity, diffusion coefficient, and relaxation time. The assumptions of the theoretical models will be tested by computer simulation. The results for osmotic coefficient, diffusion coefficient, linear viscoelasticity and steady shear viscosity will be compared with experiments. The molecular models of polyampholyte-polyelectrolyte complexes that will be developed may have far-reaching consequences in the bio-medical area, and in areas utilizing charged macromolecules as rheology modifiers. For example, protein-polyelectrolyte complexes control the rheology and lubrication properties of synovial fluid. A pragmatic industrial use of protein-polyelectrolyte complexes is to use polyelectrolytes to boost the viscosity of protein solution for coating photographic film and paper. In both cases, the associations between the protein and the polyelectrolyte directly control rheology of the complex. The proposed project is well suited for training undergraduate and graduate students in modern analytical and numerical techniques and mentoring is integrated into every aspect of the proposed research. Graduate students will work with undergraduate physics, chemistry or chemical engineering students who will be involved either through independent research for credit or through Research Experience for Undergraduates (REU) programs. The results of the proposed research will be incorporated into a course sequence on Polymer Physics, Polymer Physical Chemistry, as well as into new special topics course, Charged Macromolecules. %%%This award supports theoretical and computational research and education with an aim to develop molecular level models of solutions containing charged polymers, polyampholyte-polyelectrolyte complexes. When a polyelectrolyte (e.g. polyacrylic acid) is mixed with a polyampholyte (e.g. a protein) of the same net charge, a soluble complex is formed. The oppositely charged amino acids on the protein are bound close to the polyelectrolyte, causing an electrostatic attraction between the two. With a large excess of polyampholyte, the solution is a liquid. As more polyelectrolyte is added, the viscosity steadily increases. Once, enough polyelectrolyte is added, a reversible gel is formed. The research aims to develop molecular models describing the formation of polyampholyte-polyelectrolyte complexes under a wide range of conditions. In dilute solutions the resulting model will enable the prediction of polymer conformations, and various solution properties such as viscosity, diffusion coefficient, and relaxation time. The assumptions of the theoretical models will be tested by computer simulation and predictions for various properties will be compared with experiments. The molecular models of polyampholyte-polyelectrolyte complexes that will be developed may have far-reaching consequences in the bio-medical area, and in areas utilizing charged macromolecules as rheology modifiers. For example, protein-polyelectrolyte complexes control the rheology and lubrication properties of synovial fluid. A pragmatic industrial use of protein-polyelectrolyte complexes is to use polyelectrolytes to boost the viscosity of protein solution for coating photographic film and paper. In both cases, the associations between the protein and the polyelectrolyte directly control the rheology of the complex. The proposed project is well suited for training undergraduate and graduate students in modern analytical and numerical techniques and mentoring is integrated into every aspect of the proposed research. Graduate students will work with undergraduate physics, chemistry or chemical engineering students who will be involved either through independent research for credit or through Research Experience for Undergraduates (REU) programs. The results of the proposed research will be incorporated into a course sequence on Polymer Physics, Polymer Physical Chemistry, as well as into new special topics course, Charged Macromolecules. ***