Negative Dissociation Energy Phenomenon of Metastable H-Bonds As Revealed in Triplex DNA Hole Migration

摘要

Ab initio calculations reveal an unknown energetic phenomenon for H-bonds in the hole-trapping triplex C_p·G°C motif observed experimentally in hole migration which can explain the lower but really available oxidization possibility in C_p·G°C site. Hole trapping can considerably destabilize the C_p·G°C unit and lead to an unexpected barrier-hindered channel with a negative dissociation energy. This channel is governed by a balance between electrostatic repulsion and H-bonding attraction in the two associated moieties and different attenuations of two opposite interactions with respect to the H-bond distance. This C_p·G°C unit can be viewed as a high-energy node in a DNA wire which modulates migration of a hole into or through it via its unusual energetics. It provides useful information for understanding of an unknown type of the complicated intermolecular interactions, a novel type of "high-energy" bond, and can be applied further to interpret the hidden transport properties and the energy conversion/transfer mechanisms in the related fields.