Donor-acceptor, electronic coupling

Distance The affects of electron donor-acceptor distance on reaction rate arises because electron transfer, like any reaction, requires the wavefunctions of the reactants to mix (i.e. orbital overlap must occur). Unlike atom transfer, the relatively weak overlap which can occur at long distances (> 10 A) may still be sufficient to allow reaction at significant rates. On the basis of work with both proteins and models, it is now generally accepted that donor-acceptor electronic coupling, and thus electron transfer rates, decrease exponentially with distance kji Ve, exp . FCF where v i is the frequency of the mode which promotes reaction (previously estimated between 10 -10 s )FCF is a Franck Condon Factor explained below, and p is empirically estimated to range from 0.8-1.2 with a value of p 0.9 A most common for proteins. 

This review focuses on computational schemes that can be appHed to estimate the donor-acceptor electronic couplings in DNA. Therefore, we will ultimately be interested in a computational procedure that provides an efficient estimate of the electronic coupling when investigating a system along an MD trajectory [31]. In addition, sufficiently accurate methods and models play an important role in understanding fundamental aspects of the donor-acceptor coupling in DNA and in evaluating any procedure chosen for its efficiency in combination with an MD approach. 

The Marcus type fit shown in figure 7 implicitly assumes that the primary effect of metal substitution is to change the exothermicity, while holding constant both the reorganization energy and the donor acceptor electronic coupling. 

In this approach k is proportional to the square of the donor-acceptor electronic coupling matrix element (//DA) and a Franck-Condon term that contains the dependence of the ET rate on AGgy, X and factors related to the molecular structure,... 

Donor-Acceptor Electronic Coupling in Ruthenium-Modified Heme Proteins... 

Here AE° is the difference in reduction potential between the donor and acceptor sites (i.e. the driving force), //ab is the donor-acceptor electron coupling, and k is the reorganization energy required for electron transfer. The rate is maximized when //ab is large and k is small. The reduction potential of the site is dictated by the biological function and therefore must be within the range of the donor and acceptors. ... 

The time-dependent perturbation theory of the rates of radiative ET is based on the Born-Oppenheimer approximation [59] and the Franck Condon principle (i.e. on the separation of electronic and nuclear motions). The theory predicts that the ET rate constant, k i, is given by a golden rule -type equation, i.e., it is proportional to the product of the square of the donor-acceptor electronic coupling (V) and a Franck Condon weighted density of states FC) ... 

N. E. Miller, M. C. Wander, R. J. Cave, A Theoretical study of the electronic coupling element for electron transfer in water, J. Phys. Chem. A, 1999, 103, 1084-1093 b) E. W. Castner Jr., D. Kennedy, R. J. Cave, Solvent as electron donor donor/acceptor electronic coupling is a dynamical variable, J. Phys. Chem. A, 2000, 104, 2869-2885. 

The contributions of donor-acceptor electronic coupling, enter Equation (1) overtly... 

Consequently, then, reaction rates are generally anticipated to be sensitive to the nature of the donor-acceptor electronic coupling. 

E. W. Castner, D. Kennedy, and R. J. Cave,/. Phys. Chem. A, 104, 2869 (2000). Solvent as Electron Donor Donor/Acceptor Electronic Coupling is a Dynamical Variable. 

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