Full embedding QM/MM scheme for modeling excited state proton transfer processes

普渡大学的Lyudmila V. Slipchenko获得了化学系化学理论，模型和计算方法项目的奖项，以开发新的计算和理论工具来描述质子的转移，这些质子涉及电子被激发的分子，通常是通过吸收光。待研究的系统是在溶液中或在其他复杂环境中。 被称为激发态质子转移（ESPT）的现象是普遍存在的。它天然存在于光敏蛋白质中，在生物学中起着许多重要作用，并在DNA链之间发生，作为消散过量紫外线辐射的途径。在技术上，ESPT被用于人工光器件、荧光化学传感器，以及利用光脉冲控制局部环境的酸度。然而，ESPT途径，这是设计高效的光化学电池或光酸必不可少的机制的理解，仍然是不完整的。这项研究预计将有助于理解和最终控制ESPT过程中阐明环境（溶剂，电解质，蛋白质基质）在这些事件中的作用。这些知识将使设计新型光酸、化学传感器和人工光器件的科学家和工程师受益。在这个项目中开发和验证的算法将广泛分布，并用于化学，生物学和材料中各种光诱导过程的预测研究。Slipchenko和她的研究小组的目标是表征静态和动态环境对复杂的光化学和光物理过程的影响，如ESPT，通过（i）开发基于第一性原理的QM/MM方法（量子力学/分子力学）类型，（ii）通过创建凝聚相光化学数据库，相对于其他已建立和新兴的方法验证和基准测试该方法，和（iii）应用新开发的工具研究溶剂化光酸和蛋白质如GFP和PYP中的ESPT机制。所提出的方法的发展是基于极化量子力学/分子力学（QM/MM）方法的电子激发态，其中的环境（MM部分）是由复杂的有效碎片势（EFP）方法描述。所提出的工作提高了QM/EFP方法的准确性和适用性，通过（i）开发一个完整的嵌入QM/EFP模型，其中量子和经典系统之间的所有相互作用都考虑到量子力学，（ii）将该模型扩展到生物环境，以及（iii）开发QM/EFP激发态分子动力学算法。所提出的研究的新奇在于创建了一个独特的全嵌入QM/MM模型，并将其应用于各种复杂环境中的激发态动力学。拟议的研究有助于研究基础设施通过集成新的计算机代码在开源，免费提供libefp库和开源PSI 4，GAMESS和NWChem电子结构包，并作为Q-Chem和MOLCAS量子化学软件的开源模块。拟议的凝聚相光化学数据库包含各种环境中的各种光活性分子，将通过为扩展系统提供新开发和建立的方法的基准以及提供在线教程，为社区的量子化学教育做出贡献。

Lyudmila V. Slipchenko of Purdue University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to develop new computational and theoretical tools for describing the transfer of protons involving molecules in which the electrons have been excited, often by absorption of light. The systems to be studied are in solution or in other complex environments. The phenomenon known as excited state proton transfer (ESPT) is ubiquitous. It naturally occurs in photoactive proteins, which play many important roles in biology, and takes place between DNA strands as a pathway for dissipating excess UV radiation. In technology, ESPT is exploited in artificial photo-devices, fluorescent chemo-sensors, and for manipulating the acidity of local environment with light pulses. However, mechanistic understanding of ESPT pathways, which is essential for design of efficient photochemical cells or photoacids, remains incomplete. This research is expected to contribute to the understanding and eventual control of ESPT processes by elucidating the role of environment (solvent, electrolyte, protein matrix) in these events. This knowledge will benefit scientists and engineers designing new classes of photoacids, chemo-sensors and artificial photo-devices. The algorithms developed and validated in this project will be broadly distributed and serve for predictive studies of a variety of photo-induced processes in chemistry, biology, and materials. Slipchenko and her research group aim to characterize static and dynamic environment effects on complex photochemical and photophysical processes such as ESPT by (i) developing novel first-principles based methodology of QM/MM (Quantum Mechanics/Molecular Mechanics) type, (ii) validating and benchmarking this methodology relative to other established and emerging methods by creating a condensed-phase photochemistry database, and (iii) applying newly developed tools for investigating ESPT mechanisms in solvated photoacids and proteins such as GFP and PYP. The proposed method developments are based on polarizable quantum mechanics/molecular mechanics (QM/MM) approach for electronic excited states, in which the environment (the MM part) is described by the sophisticated Effective Fragment Potential (EFP) method. The proposed work enhances the accuracy and applicability of the QM/EFP methods by (i) developing a full embedding QM/EFP model in which all interactions between the quantum and classical systems are accounted for quantum-mechanically, (ii) extending this model to biological environments, and (iii) developing QM/EFP excited state molecular dynamics algorithms. The novelty of the proposed research is in creating a unique full embedding QM/MM model and applying it to excited state dynamics in various complex environments. The proposed research contributes to the research infrastructure byintegrating new computer codes in the open-source, freely available libefp library and in open-source PSI4, GAMESS and NWChem electronic structure packages and as open-source modules in Q-Chem and MOLCAS quantum chemistry software. The proposed condensed-phase photochemistry database, containing a variety of photoactive molecules in various environments, will contribute to quantum chemistry education in the community by providing benchmarks of newly developed and established methods for extended systems and by supplying online tutorials.