Abstract
Adenine, one of the components of DNA/RNA helices, has the ability to form self-organizing structures with cyclic hydrogen bonds (A4), similar to guanine quartets. Here, we report a computational investigation of the effect of substituents (X = NO2, Cl, F, H, Me, and NH2) on the electronic structure of 9H-adenine and its quartets (A4-N1, A4-N3, and A4-N7). DFT calculations were used to show the relationships between the electronic nature of the substituents, strength of H-bonds in the quartets, and aromaticity of five- and six-membered rings of adenine. We demonstrated how the remote substituent X modifies the proton-donating properties of the NH2 group involved in the H-bonds within quartets and how the position of the substituent and its electronic nature affect the stability of the quartets. We also showed the possible changes in electronic properties of the substituent and aromaticity of adenine rings caused by tetramer formation. The results indicate that the observed relationships depend on the A4 type. Moreover, the same substituent can both strengthen and weaken intermolecular interactions, depending on the substitution position.
Highlights
Purine derivatives play a signi cant role in medicinal chemistry and they are important intermediates for the synthesis of biologically-active nucleoside analogues, and frequently exhibit antiviral or antitumor properties.[1]
Adenine (6-amino substituted purine derivative), one of the building blocks of DNA/RNA helices, can participate in intermolecular interactions which may lead to substantial changes in its electronic structure and, in consequence, to changes in its chemical/physicochemical/biochemical properties
It should be stressed that the effects of the intermolecular interactions (H-bonding, p-stacking, etc.) on the electronic structure and molecular properties of nucleic acid bases have long been a subject of wide and intensive studies.[2]
Summary
Purine derivatives play a signi cant role in medicinal chemistry and they are important intermediates for the synthesis of biologically-active nucleoside analogues, and frequently exhibit antiviral or antitumor properties.[1]. Adenine (6-amino substituted purine derivative), one of the building blocks of DNA/RNA helices, can participate in intermolecular interactions which may lead to substantial changes in its electronic structure and, in consequence, to changes in its chemical/physicochemical/biochemical properties. In this perspective, the knowledge of the changes in the electronic structure of adenine caused by well-de ned factors, such as introduction of substituents with speci c electron donating/accepting properties, is of fundamental importance. We have analyzed the in uence of the electronic nature of the substituents on the strength of H-bonds in the quartets and aromaticity of ve- and six-membered rings of adenine
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