Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL 35487.
Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 106 91, Sweden.
Proc Natl Acad Sci U S A. 2020 Aug 4;117(31):18224-18230. doi: 10.1073/pnas.2008379117. Epub 2020 Jul 17.
Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N]) or tetrabutylphosphonium ([P]) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N][Ad]·2HO, and thymine, [P][Thy]·2HO, as well as the double salt cocrystal, [P][Ad][Thy]·3HO·2HThy. The cocrystal includes the anionic [Ad(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson-Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.
利用离子液体策略，我们报告了先前仅在计算和气相中研究过的游离阴离子碱基和碱基对盐的晶体结构。四丁基氢氧化铵([N])或四丁基磷酸氢([P])与腺嘌呤(HAd)和胸腺嘧啶(HThy)反应生成去质子化腺嘌呤的水合盐[N][Ad]·2HO 和胸腺嘧啶[P][Thy]·2HO，以及双盐共晶[P][Ad][Thy]·3HO·2HThy。共晶包括阴离子[Ad(HThy)]碱基对，这是一种在固态中稳定的结构，以前甚至没有被提出过。它表现出沃森-克里克连接性，如在 DNA 中发现的，但对于游离的中性碱基对来说是不寻常的。电子结构计算还研究了观察到的阴离子碱基及其超分子形成物和水合物的稳定性，这有助于更深入地了解当去除质子时碱基对如何结合，并突出了 DNA 链中稳定或化学转化的机制。
