title: Correlation between square of electron tunneling matrix element and donor-acceptor distance in fluctuating protein media.
abstract: Correlation between fluctuations of the square of electron tunneling matrix elementTDA2and the donor-acceptor distanceRDAin the electron transfer (ET) reaction from bacteriopheophytin anion to the primary quinone of the reaction center in the photosynthetic bacteriaRhodobacter sphaeroidesis investigated by a combined study of molecular dynamics simulations of the protein conformation fluctuation and quantum chemical calculations. We adopted two kinds ofRDA; edge-to-edge distanceREEand center-to-center distanceRCC. The value ofTDA2distributed over more than 5 orders of magnitude and the fluctuation of the value ofRDAdistributed over more than 1.8 Å for the 106instantaneous conformations of 1 ns simulation. We made analysis of the time-averaged correlation step by step as follows. We divide the 106simulation data into 1000/tparts of small data set to obtain the averaged data points of <TDA2>tand <REE>tor <RCC>t. Plotting the 1000/tsets of log10<TDA2>tas a function of <REE>tor <RCC>t, we made a principal coordinate analysis for these distributions. The slopes <βE>tand <βC>tof the primary axis are very large at small value oftand they are decreased considerably astbecomes large. The ellipticity for the distribution of <TDA2>tvs<REE>twhich can be a measure for the degree of correlation became very small whentis large, while it does not hold for the distribution of <TDA2>tvs<RCC>t. These results indicate that only the correlation between <TDA2>tand <REE>tfor largetsatisfies the well-known linear relation ("Dutton law"), although the slope is larger than the original value 1.4 Å-1. Based on the present result, we examined the analysis of the dynamic disorder by means of the single-molecule spectroscopy by Xie and co-workers with use of the "Dutton law".
authors.affiliation: Graduate School of Environmental and Human Sciences, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Nishioka
authors.affiliation: Department of General Education, Faculty of Science and Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan.
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Ueda
authors.affiliation: Graduate School of Environmental and Human Sciences, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan; Department of General Education, Faculty of Science and Technology, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kakitani
keywords: Dutton law; donor-acceptor distance; electron transfer rate; photosynthetic reaction center; protein fluctuation