Roy Bonasree, Titov Evgenii, Robinson Matthew S, Gühr Markus, Saalfrank Peter
University of Potsdam, Institute of Chemistry, Karl-Liebknecht-Straße 24-25, Potsdam 14476, Germany.
European XFEL, Holzkoppel 4, Schenefeld 22869, Germany.
J Phys Chem A. 2025 Aug 14;129(32):7352-7364. doi: 10.1021/acs.jpca.5c03342. Epub 2025 Jul 31.
Thionated nucleobases have drawn considerable attention due to their role in medical treatment and biology, which triggered studies of their photophysics and photochemistry using various experimental and theoretical techniques. In particular, vacuum ultraviolet (VUV)-induced dissociative photoionization of 2-thiouracil (2-TU) has been recently studied using synchrotron radiation [Robinson et al., , 28, 2354]. Here, using molecular dynamics simulations at the semiempirical OM2 level, we study the fragmentation dynamics of the cations of 2-TU and its isomer, 4-thiouracil (4-TU). Considering various VUV photon energies, we calculate energy-resolved mass spectra and breakdown diagrams for 2-TU and 4-TU. Remarkably, we find that the major fragments are different between the two compounds: 69 amu (CNHO) for 2-TU and 85 amu (CNHS) for 4-TU. Our simulations provide direct mechanistic insight into this observation and the fragmentation processes of thionated uracils in general.
硫代核碱基因其在医学治疗和生物学中的作用而备受关注，这引发了人们使用各种实验和理论技术对其光物理和光化学进行研究。特别是，最近利用同步辐射研究了真空紫外（VUV）诱导的2-硫尿嘧啶（2-TU）的解离光电离[罗宾逊等人， ，28，2354]。在此，我们使用半经验OM2水平的分子动力学模拟，研究了2-TU及其异构体4-硫尿嘧啶（4-TU）阳离子的裂解动力学。考虑到各种VUV光子能量，我们计算了2-TU和4-TU的能量分辨质谱和分解图。值得注意的是，我们发现这两种化合物的主要碎片不同：2-TU为69原子质量单位（CNHO），4-TU为85原子质量单位（CNHS）。我们的模拟为这一观察结果以及一般硫代尿嘧啶的裂解过程提供了直接的机理见解。
