Peccati Francesca, Mai Sebastian, González Leticia
Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Straße 17, 1090 Vienna, Austria.
Philos Trans A Math Phys Eng Sci. 2017 Apr 28;375(2092). doi: 10.1098/rsta.2016.0202.
5-Bromouracil is a nucleobase analogue that can replace thymine in DNA strands and acts as a strong radiosensitizer, with potential applications in molecular biology and cancer therapy. Here, the deactivation of 5-bromouracil after ultraviolet irradiation is investigated in the singlet and triplet manifold by accurate quantum chemistry calculations and non-adiabatic dynamics simulations. It is found that, after irradiation to the bright * state, three main relaxation pathways are, in principle, possible: relaxation back to the ground state, intersystem crossing (ISC) and C-Br photodissociation. Based on accurate MS-CASPT2 optimizations, we propose that ground-state relaxation should be the predominant deactivation pathway in the gas phase. We then employ different electronic structure methods to assess their suitability to carry out excited-state dynamics simulations. MRCIS (multi-reference configuration interaction including single excitations) was used in surface hopping simulations to compute the ultrafast ISC dynamics, which mostly involves the * and * states.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.
5-溴尿嘧啶是一种核碱基类似物，它可以在DNA链中取代胸腺嘧啶，并作为一种强大的放射增敏剂，在分子生物学和癌症治疗中有潜在应用。在此，通过精确的量子化学计算和非绝热动力学模拟，研究了紫外光照射后5-溴尿嘧啶在单重态和三重态中的失活情况。研究发现，在照射到明亮的态后，原则上有三种主要的弛豫途径：弛豫回到基态、系间窜越（ISC）和C-Br光解离。基于精确的MS-CASPT2优化，我们提出基态弛豫应该是气相中主要的失活途径。然后，我们采用不同的电子结构方法来评估它们进行激发态动力学模拟的适用性。在表面跳跃模拟中使用MRCIS（包括单激发的多参考组态相互作用）来计算超快ISC动力学，这主要涉及和*态。本文是主题为“气相、凝聚相和界面中非平衡和非统计动力学的理论与计算研究”特刊的一部分。
