Interactions between proteins and RNA, as well as between their structural fragments, are widespread in biological objects. We obtained the optimized structures of complexes of the glutathione anion with neutral molecules of uracil, thymine and cytosine. It was established that all complexes are stabilized by hydrogen bonds. The preference for various H-donors in nucleic base molecules (HN(1) or HN(3) in uracyl and thymine, N(1) or H2N in cytosine) for hydrogen bonding with the peptide has been analyzed. Chain elongation from dipeptide to tripeptide creates favorable conditions for increasing the number of hydrogen bonds in the complex. The strongest hydrogen bonds are formed with the carboxylate group of the peptide. Energy advantage of complexation with cytosine compared to other pyrimidine bases, and advantage of complexation with thymine compared to uracil have been established. The contributions of structural rearrangement of molecules, intermolecular interactions and H-bonding to the total values of potential energy and Gibbs energy of the complexation process have been discussed.
