Theory and Computer Simulations of Polyampholyte-Polyelectrolyte Complexes

聚两性电解质-聚电解质复合物的理论和计算机模拟

• 批准号: 0305203
• 负责人: Andrey Dobrynin
• 金额: $ 24万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0305203&HistoricalAwards=false
• 关键词: Theory; Computer; Simulations; Polyampholyte; Polyelectrolyte

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. ***

该奖项支持理论和计算研究和教育，旨在开发含有聚两性-聚电解质复合物的溶液的分子水平模型。当一种聚电解质与一种净电荷相同的多两性电解质（蛋白质）混合时，就会形成一种可溶性复合物。这种结合以这样一种方式发生，即蛋白质上带相反电荷的氨基酸靠近聚电解质，从而在两者之间产生静电吸引。当多两性电解质大量过剩时，每个多电解质链都被多两性电解质饱和，溶液为液体。随着聚电解质的加入，粘度稳步增加。一旦加入足够多的聚电解质，一些聚电解质分子作为聚电解质链之间的临时交联，形成可逆凝胶。该研究旨在建立分子模型，描述在广泛的聚合物和盐浓度、溶液pH以及聚合物的各种性质（如分子量和电荷分布）下聚两性聚合物-聚电解质复合物的形成。在稀溶液中，所得模型将提供聚两性聚合物-聚电解质复合物内部结构的细节，以及反离子释放和缩合对复合物形成的影响。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验证。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比较。即将开发的聚两性-聚电解质复合物的分子模型在生物医学领域以及利用带电大分子作为流变调节剂的领域可能会产生深远的影响。例如，蛋白质-多电解质复合物控制滑液的流变学和润滑特性。蛋白质-聚电解质复合物的一个实用的工业用途是使用聚电解质来提高涂覆照相胶片和纸张的蛋白质溶液的粘度。在这两种情况下，蛋白质和聚电解质之间的联系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整合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，这些学生将通过独立研究获得学分或通过本科生研究经验（REU）项目参与。研究成果将纳入高分子物理、高分子物理化学课程，以及新的专题课程“带电大分子”。该奖项支持理论、计算研究和教育，旨在开发含有带电聚合物、聚两性聚合物-聚电解质复合物的溶液的分子水平模型。当一种聚电解质（如聚丙烯酸）与一种净电荷相同的聚两性电解质（如蛋白质）混合时，就会形成一种可溶性复合物。蛋白质上带相反电荷的氨基酸与聚电解质紧密结合，在两者之间产生静电吸引。由于多两性电解质的大量过剩，该溶液为液体。随着聚电解质的加入，粘度稳步增加。一旦加入足够多的聚电解质，就会形成可逆的凝胶。该研究旨在开发描述在广泛条件下聚两性电解质复合物形成的分子模型。在稀溶液中，所得到的模型将能够预测聚合物构象，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验证，对各种性质的预测将与实验进行比较。即将开发的聚两性-聚电解质复合物的分子模型在生物医学领域以及利用带电大分子作为流变调节剂的领域可能会产生深远的影响。例如，蛋白质-多电解质复合物控制滑液的流变学和润滑特性。蛋白质-聚电解质复合物的一个实用的工业用途是使用聚电解质来提高涂覆照相胶片和纸张的蛋白质溶液的粘度。在这两种情况下，蛋白质和聚电解质之间的联系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整合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，这些学生将通过独立研究获得学分或通过本科生研究经验（REU）项目参与。研究成果将纳入高分子物理、高分子物理化学课程，以及新的专题课程“带电大分子”。* * *