Department of Chemistry, Brown University, Providence, RI, 02912, USA.
Angew Chem Int Ed Engl. 2019 Jun 3;58(23):7856-7860. doi: 10.1002/anie.201903444. Epub 2019 Apr 30.
Tautomers of the nucleobases play fundamental roles in spontaneous mutations of DNA. Tautomers of neutral cytosine have been studied in the gas phase, but much less is known about charged species. Here, we report the observation and characterization of three tautomers of deprotonated cytosine anions, [trans-keto-amino-N3H-H8b] (tKAN3H8b ), [cis-keto-amino-N3H-H8a] (cKAN3H8a ) and [keto-amino-H] (KAN1 ), produced by electrospray ionization. Excited dipole-bound states (DBSs) are uncovered for the three anions by photodetachment spectroscopy. Excitations to selected DBS vibrational levels of cKAN3H8a and tKAN3H8b yield tautomer-specific resonant photoelectron spectra. The current study provides further insight into tautomerism of cytosine and suggests a new method to study the tautomers of nucleobases using electrospray ionization and anion spectroscopy.
碱基的互变异构体在 DNA 的自发突变中起着重要作用。中性胞嘧啶的互变异构体在气相中已经得到了研究，但带电荷的物种知之甚少。在这里，我们报告了通过电喷雾电离观察和表征三种去质子化胞嘧啶阴离子的互变异构体，[反式-酮基-氨基-N3H-H8b]（tKAN3H8b）、[顺式-酮基-氨基-N3H-H8a]（cKAN3H8a）和[酮基-氨基-H]（KAN1）。通过光电子谱探测到三种阴离子的激发偶极束缚态（DBS）。对 cKAN3H8a 和 tKAN3H8b 的选定 DBS 振动能级的激发产生了互变异构体特异性共振光电子能谱。本研究进一步深入了解了胞嘧啶的互变异构现象，并提出了一种使用电喷雾电离和阴离子光谱研究碱基互变异构体的新方法。
