Evaluation of the effect of real substituents on the strength of hydrogen bonds between adenine-thymine base pair

Document Type : Research Article


1 Chemistry department- Faculty of science- University of Sistan and Baluchestan

2 Department of chemistry, faculty of science, university of Sistan & Baluchestan


In this study, using density functional theory, atoms in molecules and natural bonding orbital’s analyses, the strength of individual hydrogen bonds and the total interaction energy in the thymine-adenine (TA) base pair containing deoxyribose(d) and phosphate(p) substituents, was evaluated. The results of the absolute electron energies show that the structures containing the substituents are more stable than the TA base pair. In addition, according to the results of the hydrogen bonding energy, the binding of deoxyribose to adenine increase the total hydrogen bond strength more than binding this substituent to thymine. In all structures, deoxyribose binding increases N-H…N hydrogen bond strength and decreases N-H…O bond strength. While phosphate group modulates the additive effect of deoxyribose on hydrogen bond strength. It is interesting to note that the C-H...O bond is weaker than the other hydrogen bonds, but the mentioned substituents affect this hydrogen bond more than others. Also, the hydrogen bond of N-H ...N is stronger than the other hydrogen bonds and the highest of the energy value of this bond belongs to the TA-d structure. It also has the highest total hydrogen bond energy. Moreover, four parameters were introduced as suitable descriptors for evaluating the hydrogen bonding of this system.


Main Subjects