The Incorporation of Quantum Effects in the Simulation of Proton Transfer Reactions

理论与计算化学项目支持圣母大学的哈默斯-希弗教授，作为青年科学家职业计划的一部分。本研究的目的是开发和应用新的方法来模拟涉及多个质子转移反应的动力学过程。为了模拟质子转移反应，必须发展结合被转移氢原子量子力学行为的方法。在表面跳跃方法中，如分子动力学量子跃迁（MDQT），轨迹分裂成分支，每个分支分配给特定的质子量子态，因此分支过程（即涉及多个通道或途径的过程）被准确描述。然而，将MDQT直接扩展到涉及多个质子转移步骤的过程在计算上是不可行的。提出的新方法MC-MDQT将MDQT与多构型（MC）自洽场方法相结合，将正确描述分支过程，并允许对多个氢原子进行量子力学处理。这种方法将适用于两类系统。第一个是质子沿着氢键水分子的线性链传递。这是一个重要的过程，因为在细菌视紫红质和光合反应中心等重要的生物系统中，质子的远距离快速传输被认为是沿着这样的链发生的。将研究的第二类系统是酶中的氢转移，如酒精脱氢酶，它在糖酵解中起着至关重要的作用。动力学同位素效应实验表明，氢隧穿在多种酶反应中都很重要。这些应用的目的是阐明质子转移反应的基本物理原理，并阐明这些重要的生物学反应的详细机制。这项职业补助金的教育目标是促进计算机模拟在有机化学和生物化学领域的广泛应用。计算机模拟课程已经设计好了。这个项目的一个成果是创建一个计算机实验室工作手册，以及一本教科书，这将促进其他大学此类课程的发展。一般的质子转移反应包括氢原子原子核从供体到受体的传递。实验表明，氢原子可以穿过这种反应所需的能量垒。这项研究将集中在结合量子力学行为的方法上，比如为了模拟质子转移反应而穿隧。这项职业补助金的教育目标是促进计算机模拟在有机化学和生物化学领域的广泛应用。计算机模拟课程已经设计好了。本课程由三部分组成：讲座介绍计算机仿真的基本概念；计算机实验室提供分子建模的实践经验，而独立研究激励学生追求未来的项目。这个项目的一个成果是创建一个计算机实验室工作手册，以及一本教科书，这将促进其他大学此类课程的发展。

The Theoretical and Computational Chemistry program is supporting Professor Hammes-Schiffer at the University of Notre Dame as part of the CAREER program for young scientists. The objective of this research is to develop and apply new methods for simulating dynamical processes involving multiple proton transfer reactions. In order to simulate proton transfer reactions, methods that incorporate the quantum mechanical behavior of the hydrogen atoms being transferred must be developed. In surface-hopping methods such as molecular dynamics with quantum transitions (MDQT), trajectories split into branches that are each assigned to a particular proton quantum state, so branching processes (i.e. processes involving multiple channels or pathways) are described accurately. The direct extension of MDQT to processes involving multiple proton transfer steps, however, is not computationally feasible. The proposed new method, MC-MDQT, combines MDQT with a multiconfigurational (MC) self-consistent-field approach and will describe branching processes properly as well as allow the quantum mechanical treatment of multiple hydrogen atoms. This method will be applied to two classes of systems. The first is proton transport along linear chains of hydrogen-bonded water molecules. This is an important process because the rapid transport of protons over large distances in biologically important systems such as bacteriorhodopsin and photosynthetic reaction centers is thought to occur along such chains. The second class of systems that will be studied is hydrogen transfer in enzymes such as alcohol dehydrogenase, which plays a vital role in glycolysis. Kinetic isotope effect experiments indicate that hydrogen tunneling is significant in a variety of enzyme reactions. The goal of these applications is to elucidate the underlying physical principles of proton transfer reactions and to clarify the detailed mechanisms of these biologically important reactions. The educational objectives of this Carreer grant are to promote the wider use of computer simulations in the areas of organic chemistry and biochemistry. A course in computer simulations has already been designed. An outgrowth of this project is the creation of a computer lab workbook, as well as a textbook which will facilitate the development of such courses at other universities. A general proton transfer reaction involves the passing of a hydrogen atom nucleus from a donor to an acceptor. Experiments have shown that the hydrogen atom can tunnel through an energy barrier required for such a reaction. This research will focus on methods that incorporate quantum mechanical behavior, such as tunneling in order to simulate proton transfer reactions. The educational objectives of this Carreer grant are to promote the wider use of computer simulations in the areas of organic chemistry and biochemistry. A course in computer simulations has already been designed. The course consists of three parts: The lectures convey the fundamental concepts for computer simulation; Computer labs provide hands on experience with molecular modeling, while independent research motivates sutdents to pursue future projects. An outgrowth of this project is the creation of a computer lab workbook, as well as a textbook which will facilitate the development of such courses at other universities.