arXiv subjects

Divya Tripathi

Publications and source records attributed to Divya Tripathi.

5 recordsLinked to original sources

arXiv2026

The Effect of Base-Pairing on the Shape Resonances of Nucleobases

In this work, we have studied the effect of base-pairing on the shape resonances of guanine and cytosine nucleobases. Among the seven {\pi}* resonances we identified in the guanine-cytosine (GC) anion radical, three were centered on cytosine, and the remaining were guanine-centered. Relative to the isolated bases, upon base pair formation, the cytosine resonances were red shifted, while the guanine-centered states showed an opposite trend - where their energy was blue shifted. In addition to the electronic interactions, geometric distortion and basis set superposition error plays a crucial role in the resonance positions and widths of the GC radical anion. The electronic interaction from the complementary base seems to have a larger effect on the stabilization of the anionic resonances than the surrounding environment.

physics.chem-ph↗

arXiv2025

The Effect of Aqueous Medium on Nucleobase Shape Resonances: Insights from Microsolvation

We have studied the effect of microhydration on the shape resonances of uracil nucleobase. The resonance parameters were determined using the resonance via Pad\'e approach along with the efficient wave function-based EA-EOM-DLPNO-CCSD method. Our results showed that the uracil resonances become stabilized with an increase in the extent of microsolvation. The energy of the resonances decreased, and the lifetime increased as the number of water molecules surrounding uracil was increased. It showed that ten water molecules are sufficient to make the lowest shape resonance of uracil a bound radical anionic state. Our results also indicate that the lowest energy resonance state may become a bound state under bulk solvation.

physics.chem-ph↗

arXiv2022

Electron Attachment to Wobble Base Pairs

We have analyzed the low-energy electron attachment to wobble base pairs using the equation motion coupled cluster method and extended basis sets. A doorway mechanism exists for the attachment of the additional electron to the base pairs, where the initially formed dipole-bound anion captures the incoming electron. The doorway dipole-bound anionic state subsequently leads to the formation of a valence-bound state, and the transfer of extra electron occurs by mixing of electronic and nuclear degrees of freedom. The formation of the valence-bound anion is associated with proton transfer in hypoxanthine-cytosine and hypoxanthine-adenine base pairs, which happens through a concerted electron-proton transfer process. The calculated rate constant for the dipole-bound to valence-bound transition in wobble base pairs is slower than that observed in the Watson-Crick guanine-cytosine base pair.

physics.chem-ph↗

arXiv2021

A Doorway mechanism for Electron Attachment Induced DNA Strand Break

We report a new doorway mechanism for the dissociative electron attachment to genetic materials. The dipole-bound state of the nucleotide anion acts as the doorway for electron capture in the genetic material. The electron gets subsequently transferred to a dissociative σ* type anionic state localized on a sugar-phosphate or a sugar-nucleobase bond, leading to their cleavage. The electron transfer is mediated by the mixing of electronic and nuclear degrees of freedom. The cleavage rate of the sugar-phosphate bond predicted by this new mechanism is higher than that of the sugar-nucleobase bond breaking, and both processes are considerably slower than the formation of a stable valence-bound anion. The new mechanism explains the relative rates of electron attachment induced bond cleavages in genetic materials.

physics.chem-ph↗

arXiv2020

Water mediated Electron Attachment to Nucleobases: Surface-bound vs Bulk Solvated Electrons

We have investigated the electron attachment dynamics of uracil in water using accurate wave-function and QM/MM methods. The initial electron attached state is found to be localized on the water and mixing of electronic and nuclear degrees of freedom leads to the transfer of electron from the water to the uracil. The water molecules around the uracil stabilize the uracil bound anion by creating an extensive hydrogen-bonding network. The presence of the bulk water environment accelerates the rate of electron attachment to uracil and the complete electron transfer from water to the uracil happens at a picosecond time scale. The degree of solvation of the aqueous electron can lead to a difference in the initial stabilization of the uracil bound anion but at a longer time scale the anion formed due to the attachment of both surface-bound and bulk solvated electrons behaves similarly.

physics.chem-ph↗