An experimental and theoretical vibrational study of interaction of adenine and thymine with artificial seawaters: A prebiotic chemistry experiment

•Interaction nucleic acid bases/seawater is an important issue for prebiotic chemistry.•Several elements of seawater play important roles in the living beings.•Sr2+ interacts with thymine, thus it could be important for the prebiotic chemistry.•Adenine interacts with all cations of artificial seawaters.

Nucleic acid bases play important roles in living beings. Thus, their interaction with salts the prebiotic Earth could be an important issue for the understanding of origin of life. In this study, the effect of pH and artificial seawaters on the structure of adenine and thymine was studied via parallel determinations using FT-IR, Raman spectroscopy and theoretical calculations. Thymine and adenine lyophilized in solutions at basic and acidic conditions showed characteristic bands of the enol-imino tautomer due to the deprotonation and the hydrochloride form due to protonation, respectively. The interaction of thymine and adenine with different seawaters representative of different geological periods on Earth was also studied. In the case of thymine a strong interaction with Sr2+ promoted changes in the Raman and infrared spectra. For adenine changes in infrared and Raman spectra were observed in the presence of salts from all seawaters tested. The experimental results were compared to theoretical calculations, which showed structural changes due to the presence of ions Na+, Mg2+, Ca2+ and Sr2+ of artificial seawaters. For thymine the bands arising from C4C5 and C6O stretching were shifted to lower values, and for adenine, a new band at 1310 cm−1 was observed. The reactivity of adenine and thymine was studied by comparing changes in nucleophilicity and energy of the HOMO orbital.

Graphical abstract(a) Interaction of metal with thymine. (b) Interaction of metal with adenine.Figure optionsDownload full-size imageDownload as PowerPoint slide