As a polycation with diverse applications in biomedical and environmental engineering, polyethylenimine (PEI) can be synthesized with varying degrees of branching, polymerization, and can exist in different protonation states. There have been some interests in molecular modeling of PEI at all‐atom or coarse‐grained (CG) levels, but present CG models are limited to linear PEIs. Here we present the methodology to systematically categorize bond lengths, bond angles and dihedral angles, which allows us to model branched PEIs. The CG model was developed under the Martini scheme based on eight ~600 Da PEIs, with four different degree of branching at two different protonation states. Comparison of the CG model with all‐atom simulations shows good agreement for both local (distributions for bonded interactions) and global (end‐to‐end distance, radius of gyration) properties, with and without salt. Compatibility of the PEI model with other CG bio‐molecules developed under the Martini scheme will allow for large‐scale simulations of many PEI‐enabled processes. © 2018 Wiley Periodicals, Inc.

中文翻译：

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聚乙烯亚胺的马提尼粗粒模型

作为一种在生物医学和环境工程中具有多种应用的聚阳离子，聚乙烯亚胺 (PEI) 可以合成不同程度的支化、聚合，并且可以以不同的质子化状态存在。在全原子或粗粒度 (CG) 水平上对 PEI 的分子建模有一些兴趣，但目前的 CG 模型仅限于线性 PEI。在这里，我们介绍了系统地对键长、键角和二面角进行分类的方法，这使我们能够对支链 PEI 进行建模。CG 模型是在基于八个~600 Da PEI 的 Martini 方案下开发的，在两种不同的质子化状态下具有四种不同的支化度。CG 模型与全原子模拟的比较表明，局部（键相互作用的分布）和全局（端到端距离，旋转半径）特性，有盐和无盐。PEI 模型与在 Martini 方案下开发的其他 CG 生物分子的兼容性将允许对许多启用 PEI 的过程进行大规模模拟。© 2018 Wiley Periodicals, Inc.