Crystallographic evidence of Watson–Crick connectivity in the base pair of anionic adenine with thymine

Significance All genetic information on Earth is encrypted in DNA and RNA with the nucleobases and their pairs being the main information units. There are strict established rules how nucleobases can interact between each other in the DNA. These rules can though be affected by external factors such as radiation causing formation of the deprotonated charged species. Although such species are extremely unstable and low in abundance, they may affect local connectivity and introduce wrong units in the DNA chain, so proper characterization of their interactions is of enhanced importance. Here we could obtain anionic nucleobases in stable form in the solid state, opening the possibility to study them crystallographically and develop theoretical models for real biological systems.