School of Physical Sciences, University of Science and Technology of China, Hefei 230000, China.
National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621999, China.
J Phys Chem B. 2020 Oct 29;124(43):9570-9578. doi: 10.1021/acs.jpcb.0c06251. Epub 2020 Oct 19.
There is no doubt that electric fields of a specific frequency and intensity could excite certain vibrational modes of a macromolecule, which alters its mode coupling and conformation. Motivated by recent experiments and theories, we study the mode coupling between the Fe-CO mode and CO-stretch mode and vibration energy transfer among the active site and proteins in carboxyhemoglobin (HbCO) under different electric fields using the quasi-static two-dimensional infrared spectra. This study uses iron-porphyrin-imidazole-CO and two distal histidines in HbCO as the subsystem. The potential energy and dipole moment surfaces of the subsystem are calculated using an all-electron ab initio (B3LYP-D3(BJ)) method with the basis set Lanl2dz for the Fe atom and 6-31G(d,p) for C, H, O, and N atoms. Although the subsystem is reduced dimensionally, the anharmonic frequency and anharmonicity of the CO-stretch mode show excellent agreement with experimental values. We use the revealing noncovalent interaction method to confirm the hydrogen bond between the H atom of the His63 and the CO molecule. Our study confirms that the mode coupling between the Fe-CO mode and CO-stretch mode does not exist when the subsystem is free of electric field perturbation, which is coupled when the electric field is -0.5142 V/nm. In addition, with the increases of distance between the active site and the His92, there is no vibrational energy transfer between them when the electric field is 1.028 V/nm. We believe that our work could provide new ideas for increasing the dissociation efficiency of the Fe-CO bond and theoretical references for experimental research.
毫无疑问，特定频率和强度的电场可以激发大分子的某些振动模式，从而改变其模式耦合和构象。受最近的实验和理论的启发，我们使用准静态二维红外光谱研究了不同电场下羧基血红蛋白（HbCO）中 Fe-CO 模式与 CO 伸缩模式之间的模式耦合以及活性位点与蛋白质之间的振动能量转移。该研究使用铁卟啉-咪唑-CO 和 HbCO 中的两个远端组氨酸作为子系统。使用全电子从头算（B3LYP-D3（BJ））方法和 Lanl2dz 基组计算子系统的位能和偶极矩表面，用于 Fe 原子和 6-31G（d，p）用于 C、H、O 和 N 原子。尽管子系统的维度降低了，但 CO 伸缩模式的非谐频率和非谐性与实验值具有极好的一致性。我们使用揭示非共价相互作用的方法来确认 His63 的 H 原子与 CO 分子之间的氢键。我们的研究证实，在没有电场扰动的情况下，子系统之间不存在 Fe-CO 模式与 CO 伸缩模式之间的模式耦合，当电场为-0.5142 V/nm 时，它们会发生耦合。此外，随着活性位点与 His92 之间距离的增加，当电场为 1.028 V/nm 时，它们之间没有振动能量转移。我们相信我们的工作可以为提高 Fe-CO 键的解离效率提供新的思路，并为实验研究提供理论参考。
