Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC), CONICET─UNC, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
Dpto. de Fisicoquímica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
J Phys Chem A. 2022 Mar 3;126(8):1403-1411. doi: 10.1021/acs.jpca.1c10651. Epub 2022 Feb 17.
The collision-induced dissociation of the protonated cytosine-guanine pair was studied using tandem mass spectrometry (MS) coupled to infrared multiple photon dissociation spectroscopy with the free electron laser at Orsay (CLIO) to determine the structure of the CH and GH ionic fragments. The results were rationalized with the help of electronic structure calculations at the density functional theory level with the B3LYP/6-311++G(3df,2p) method. Several tautomers of each fragment were identified for the first time, some of which were previously predicted by other authors. In addition, two unexpected and minor tautomers were also found: cytosine keto-imino [CKI(1,2,3,4)H] and guanine keto-amino [GKA(1,3,7)H]. These results highlight the importance of the DNA base tautomerization assisted by inter- and intramolecular proton or hydrogen transfer within the protonated pairs.
采用串联质谱（MS）结合 Orsay（CLIO）自由电子激光的红外多光子解离光谱研究了质子化胞嘧啶-鸟嘌呤对的碰撞诱导解离，以确定 CH 和 GH 离子片段的结构。借助密度泛函理论（B3LYP/6-311++G（3df，2p）方法）的电子结构计算对结果进行了合理化。首次确定了每个片段的几种互变异构体，其中一些是先前其他作者预测的。此外，还发现了两种意外的次要互变异构体：胞嘧啶酮亚氨基[CKI（1,2,3,4）H]和鸟嘌呤酮氨基[GKA（1,3,7）H]。这些结果强调了在质子化对中通过分子内和分子间质子或氢转移辅助 DNA 碱基互变异构的重要性。
