Ol’ha O Brovarets
National Academy of Sciences of Ukraine, Ukraine
Title: Novel routes of the tautomeric wobbling of the biologically important reverse Watson-Crick, Hoogsteen and reverse Hoogsteen G∙C DNA base pairs
Biography
Biography: Ol’ha O Brovarets
Abstract
For the first time we have explored the structural diversity of the biologically-important guanine∙cytosine (G∙C) DNA base pairs - reverse Watson-Crick G*∙C*(rWC), Hoogsteen G*O6∙C*(H) and reverse Hoogsteen G*O6·C*(rH) mispairs using quantum-mechanical calculations at the MP2/aug-cc-pVDZ//B3LYP/6-311++G(d,p) level of QM theory in the continuum with ε=1 under normal conditions in combination with Bader's Quantum Theory of Atoms in Molecules (QTAIM). It was theoretically demonstrated that these rWC/H/rH base mispairs possess unique ability to perform tautomeric transition into the base pairs with wobble (w) geometry and vice versa through the intramolecular single proton transfer along the intermolecular H-bonds accompanied with the mutual shifting of the bases inside the base pair into the minor or major DNA grooves. We have established that rWC/H/rH↔w transitions lead both to the structural, so to the tautomeric changes of the base pairs. In each case these structurally-tautomeric transitions occur through two different pathways via the two transitions states (TSs) as tight G+∙C- ion pairs. In the cases of the reverse Watson-Crick G*∙C*(rWC) and Hoogsteen G*O6∙C*(H) base mispairs this tautomeric wobbling is preceded by the sequential double proton transfer along the intermolecular H-bonds. Moreover, formed wobble base mispairs are able to convert into their trans-conformers due to the rotation of the non-bonded OH or NH groups. All of the investigated G∙C DNA base pairs are tightly connected with each other through the number of reaction pathways due to the SPT or DPT, rWC/H/rH↔w or cys↔trans transitions.