Modeling Macroions – Filling the Gap Between Ions and Colloids

在化学学部的大分子、超分子和纳米化学（MSN）项目的支持下，阿克伦大学的Mesfin Tsige正在使用计算机模拟来模拟带有多个电荷的大分子（称为巨离子）的自组装过程。当放置在溶液中时，电荷位点之间的库仑力导致宏观离子自组装成大型复杂结构。齐格博士和他的学生将使用计算机模型来研究组装过程，该模型可以跟踪数十万到数百万个原子的运动。他们的发现有助于解释实验观察结果，也可能影响我们对其他重要大离子（如蛋白质和DNA）自我组装的理解。该项目将通过为研究生提供研究机会，以及通过NSF-REU中心在聚合物科学和聚合物工程学院的本科生，以及来自当地圣文森特-圣文森特大学的高中生提供研究机会，帮助培养下一代科学家。玛丽的学校。此外，齐格博士和他的团队还访问了当地为大量少数民族提供服务的学校，向学生介绍科学概念，并鼓励他们从事STEM领域的职业。由于涉及大量原子和库仑力的长程性质，宏观离子自组装的计算机模拟具有挑战性。一个典型的模拟跟踪25-50个巨离子的自组装，这些巨离子被数千个反离子和数百万个溶剂分子包围，形成大型的“黑莓状”结构。齐格博士使用了一种通用的粗粒度模型来进行分子动力学模拟，在这种模型中，原子群被组合在一起，并用珠子来表示。他们的方法减小了系统的尺寸，使大型组件的模拟成为可能，同时保留了分子水平的细节。他们将观察组装形成的初始阶段，以发展对自组装如何受到宏观离子大小、电荷密度、溶剂极性以及反离子和共离子存在的影响的基本理解。该项目将通过提供从实验室测量中难以或有时不可能获得的见解来补充宏离子组装的实验研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Chemistry Division, Mesfin Tsige of the University of Akron is using computer simulation to model the self-assembly of very large molecules with multiple charges, called macro-ions. When placed in solution, coulombic forces between charge sites cause macro-ions to self-assemble into large complex structures. Dr. Tsige and his students will study the assembly process using computer models that track the motion of hundreds of thousands to millions of atoms. Their discoveries help interpret experimental observations and could also impact our understanding of the self-assembly of other important macro-ions, such as proteins and DNA. The project will help to train the next generation of scientists by providing research opportunities for graduate students, as well as undergraduate students through the NSF-REU center at the School of Polymer Science and Polymer Engineering, and high school students from the local St. Vincent-St. Mary School. In addition, Dr. Tsige and his group visit local schools that serve large numbers of minorities, introducing their students to scientific concepts and encouraging them to pursue careers in STEM. Computer simulation of macro-ion self-assembly is challenging due to the large numbers of atoms involved and long-range nature of coulombic forces. A typical simulation tracks the self-assembly of 25-50 macro-ions, which are surrounded by thousands of counterions and millions of solvent molecules, into large 'blackberry-like' structures. Dr. Tsige uses molecular dynamics simulations with a versatile coarse-grained model in which groups of atoms are combined and represented by beads. Their approach reduces the size of the system, making the simulation of large assemblies possible, while retaining molecular-level detail. They will observe the initial stages of assembly formation to develop a fundamental understanding of how self-assembly is affected by macro-ion size, charge density, and solvent polarity, as well as the presence of counter ions and co-ions. The project will complement experimental studies of macro-ion assembly by providing insights that are difficult or sometimes impossible to get from laboratory measurements.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.