Election of cytosine, guanine, thymine and adenine as the components of the information biopolymers was a complex process, influenced by several factors. Among them, the intermolecular interactions may have played a determinant role. Thus, a deep understanding of the intermolecular interactions between nucleobases and other prebiotic molecules may help understand the first instants of chemical evolution. Following this hypothesis, we present here a combined spectroscopic and computational study of theobromine2-adenine and thebromine-adenine2 trimers. While adenine is a nucleobase, theobromine was probably part of the prebiotic chemistry. The trimers were formed in jets and probed by a combination of UV and IR spectroscopic techniques. The spectra were interpreted on the light of the predictions obtained using density functional methods. The results suggest the existence of a subtle balance between formation of hydrogen bonds and p-p interactions. Thus, while theobromine2-adenine tends to form complex in stacked structures, theobromine-adenine2 prefers formation of planar structures, maximizing the interaction by hydrogen bonds. The small energy difference between planar and stacked structures, highlights the importance of accurately model the dispersion forces in the functionals to produce reliable predictions.
Sugars are, together with amino acids and nucleobases, fundamental building blocks of the cell. They are involved in many fundamental processes and specially they play relevant roles as part of...
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