Temperature dependence of the inelastic electron tunneling

Abstract

The property of the anomalous inverted region in the energy gap law which was found in the recent non-Condon theory of the electron transfer (ET) in protein media is investigated in more detail in relation to the inelastic electron tunneling. The physical aspect of the inelastic electron tunneling is theoretically discussed and schematically explained. Since it was previously shown that the inelastic electron tunneling mechanism worked significantly due to an exponential-like decay of the autocorrelation function of the electron tunneling matrix element with a small correlation time at 300 K, we investigated whether the similar exponential-like decay of the autocorrelation function is obtained or not and how the correlation time is changed at low temperatures. For this purpose, numerical calculations for the electron tunneling matrix element in the ET at 77 K from bacteriopheophytin (Bph) anion to the primary quinone in the reaction center of photosynthetic bacteria Rhodobacter sphaeroides are made. The results are that almost exponential-like decay of the autocorrelation function was obtained even at 77 K and the half decay time was of the similar magnitude to that at 300 K. Physical meaning of this temperature dependence is discussed.

Average Electron Tunneling Route of the Electron Transfer in Protein Media

“…Then, a specific feature of the inelastic tunneling mechanism will not appear in the electronic factor, but it appears in the nuclear factor. 37,38 The Met route is formed by the tunneling currents starting from the methyl group attached to C5 of quinone to the carbon atom C12 in the ring III of bacteriopheophytin. The molecular orbital (MO) coefficients of the three hydrogen atoms of the methyl group is largely regulated by the hyperconjugation effect with the π-conjugated ring of quinone.…”

“…We have also seen that the σ̃ ab 2 map is similar to the ⟨ J̃ ab 2 ⟩ map. Then, a specific feature of the inelastic tunneling mechanism will not appear in the electronic factor, but it appears in the nuclear factor. , …”

“…The procedures for molecular dynamics (MD) simulations reported in this paper were essentially same as those described in refs , , and . The initial configuration of the reaction center of Rhodobacter sphaeroides was obtained from the Protein Data Bank, entry code .…”

“…The procedures for QC calculations reported in this paper were essentially the same as described in refs and except one point which we describe below. The chemical structures of donor and acceptor which we adopted in calculating ϕ D and ϕ A were shown in ref .…”