The peculiar role of cytosine in nucleoside conformational behaviour: Hydrogen bond donor capacity of nucleic bases

According to theoretical calculations, both 2'-deoxycytidine and cytidine s how a different energetical behaviour as compared to the other nucleosides. A C-H . . .O intramolecular hydrogen bond is suspected to greatly influenc e the conformational behaviour of the nucleosides. The donor atom is the H6 (H8) atom of the pyrimidic (puric) nucleic base and the acceptor atom is t he O5' atom of the sugar. In the present work, we assess the hydrogen bond donor capacity of the H6/H8 hydrogen atom according to the base, by calcula ting deprotonation energies and electrostatic potentials. This allows us to state precisely that the peculiar behaviour of deoxycytidine expresses its elf in the South conformation, and that cytidine does not behave like deoxy cytidine.