Unbiased charge oscillations in DNA monomer-polymers and dimer-polymers

TL;DR

This study investigates charge oscillations in DNA monomer- and dimer-polymers using a tight-binding model, revealing how charge transfer rates depend on polymer length and structure, with implications for DNA-based electronic devices.

Contribution

It provides an analytical and numerical analysis of charge transfer in DNA polymers, highlighting the effects of sequence structure and parameter variations on transfer efficiency and spectral properties.

Findings

Power law fits better than exponential for charge transfer decay.

Increasing parameter complexity steepens charge transfer decay.

Charge probabilities exhibit palindromicity and eigenspectrum dependence.

Abstract

We call {\it monomer} a B-DNA base-pair and examine, analytically and numerically, electron or hole oscillations in monomer- and dimer-polymers, i.e., periodic sequences with repetition unit made of one or two monomers. We employ a tight-binding (TB) approach at the base-pair level to readily determine the spatiotemporal evolution of a single extra carrier along a $N$ base-pair polymer. We study HOMO and LUMO eigenspectra as well as the mean over time probabilities to find the carrier at a particular monomer. We use the pure mean transfer rate $k$ to evaluate the easiness of charge transfer. The inverse decay length $\beta$ for exponential fits $k(d)$, where $d$ is the charge transfer distance, and the exponent $\eta$ for power law fits $k(N)$ are computed; generally power law fits are better. We illustrate that increasing the number of different parameters involved in the TB description, the fall of $k(d)$ or $k(N)$ becomes steeper and show the range covered by $\beta$ and $\eta$. Finally, both for the time-independent and the time-dependent problem, we analyze the {\it palindromicity} and the {\it degree of eigenspectrum dependence} of the probabilities to find the carrier at a particular monomer.