Gate Gregory, Williams Ann, Boldissar Samuel, Šponer Jiří, Szabla Rafal, de Vries Mattanjah
Department of Chemistry and Biochemistry, University of California, Santa Barbara, California, USA.
Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic.
Photochem Photobiol. 2024 Mar-Apr;100(2):404-418. doi: 10.1111/php.13897. Epub 2023 Dec 20.
2,6-Diaminopurine (2,6-dAP) is an alternative nucleobase that potentially played a role in prebiotic chemistry. We studied its excited state dynamics in the gas phase by REMPI, IR-UV hole burning, and ps pump-probe spectroscopy and performed quantum chemical calculations at the SCS-ADC(2) level of theory to interpret the experimental results. We found the 9H tautomer to have a small barrier to ultrafast relaxation via puckering of its 6-membered ring. The 7H tautomer has a larger barrier to reach a conical intersection and also has a sizable triplet yield. These results are discussed relative to other purines, for which 9H tautomerization appears to be more photostable than 7H and homosubstituted purines appear to be less photostable than heterosubstituted or singly substituted purines.
2,6 -二氨基嘌呤（2,6 - dAP）是一种替代性核碱基，可能在生命起源前的化学过程中发挥了作用。我们通过共振增强多光子电离（REMPI）、红外 - 紫外空穴烧蚀和皮秒泵浦 - 探测光谱研究了其在气相中的激发态动力学，并在SCS - ADC(2)理论水平上进行了量子化学计算以解释实验结果。我们发现9H互变异构体通过其六元环的褶皱进行超快弛豫的势垒较小。7H互变异构体到达锥形交叉点的势垒较大，并且三线态产率也相当可观。相对于其他嘌呤讨论了这些结果，对于其他嘌呤，9H互变异构化似乎比7H更具光稳定性，并且同取代嘌呤似乎比杂取代或单取代嘌呤的光稳定性更低。
