Electronic parameters for charge transfer along DNA

Abstract

We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The pi molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wave functions and energies of DNA bases are discussed and then used for calculating the corresponding wave functions of the two B-DNA base-pairs (adenine-thymine and guanine-cytosine). The obtained HOMO and LUMO energies of the bases are in good agreement with available experimental values. Our results are then used for estimating the complete set of charge transfer parameters between neighboring bases and also between successive base-pairs, considering all possible combinations between them, for both electrons and holes. The calculated microscopic quantities can be used in mesoscopic theoretical models of electron or hole transfer along the DNA double helix, as they provide the necessary parameters for a tight-binding phenomenological description based on the pi molecular overlap. We find that usually the hopping parameters for holes are higher in magnitude compared to the ones for electrons. Our findings are also compared with existing calculations from first principles.

Electronic structure and carrier transfer in B-DNA monomer polymers and dimer polymers: Stationary and time-dependent aspects of a wire model versus an extended ladder model

“…This is expressed in Table I, where we show all energies in eV with accuracy of 0.1 eV. Our numerical results for type 43 . All energies are given in eV.…”

“…. , 2N , according to the expression β = 2(µ − 1) + σ. Schematically, 43 . In other words, within TB I, a monomer is considered as a single site, characterized by the index µ, while, within TB II, a base is considered as a single site, characterized by the index β.…”

“…Using the HOMO or LUMO energies of the bases that constitute a base pair, we can estimate the HOMO or LUMO energy of the base pair 43 . Specifically, supposing that |ψ bp = C 1 |ψ b1 + C 2 |ψ b2 , and taking the time-independent Schrödinger equation H |ψ bp = E |ψ bp we find that the base pair eigenen-…”

“…between the two bases that constitute a base pair. However, due to the weak hydrogen bonding between the bases that constitute a base pair, t is very small 43 , of the order of 10 meV. As a result, practically, E 1,2 ≈ E b1 , E b2 (with accuracy of 1 meV).…”

“…For TB I, there is a minigap a little greater than 0.340 eV, mainly due to the different HOMO on-site energies of the two base pairs (−8.0 eV for G-C, −8.3 eV for A-T) 43 . For TB II, four minibands are formed approximately around the HOMO on-site energies of the four bases (−9.0 eV for T, −8.8 eV for C, −8.3 eV for A and −8.0 eV for G) 43 , with three relevant minigaps (0.205 eV, 0.362 eV, 0.334 eV). Two of these minibands are very narrow.…”