IPPP-CLOPPA Analysis of the Influence of the Methylation on the Potential Energy and the Molecular Polarizability of the Hydrogen Bonds in the Cytosine–Guanine Base Pair

Abstract

The IPPP-CLOPPA method is applied to investigate the influence of a methyl group on the energy of the hydrogen bonds and the potential energy curve of the bridge protons in model compounds, which mimic the methylated and unmethylated cytosine-guanine base pairs. On the same grounds, this influence on the polarizability of the intermolecular hydrogen bonds of these compounds is also addressed, in order to determine whether this linear response property provides a significant proof of the electronic mechanisms that affect the stabilization of the hydrogen bonds. Results obtained show that the methyl electronic system delocalizes on the hydrogen bond region, and changes of these intermolecular hydrogen bonds are due to this effect of delocalization.

Influence of the Number, Nature and Position of Methyl Posttranscriptional Modifications on Nucleobase Stacking in RNA

“…Greater stacking strength of the modified dimers compared to their corresponding canonical counterparts is likely due to enhanced dispersion interactions originating from methyl groups. Although the enhancement of stacking strength due to base methylation contrasts the previously‐observed minimal effect of methylation hydrogen‐bonding strength RNA base pairs, [14–16] studies suggest that methylation signiificantly affects the strength of hydrogen bonds in DNA base pairs [34–36] . This correlates with the fact that methylation is a natural method of gene silencing, and is expected to cause changes in the strength and characteristics of both the hydrogen bonding interactions involved in the base pairs, as well as the base‐base stacking interactions.…”