| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2002: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Electron transfer (ET) through protein media is, in general, a long-range ET Namely, ETs take place from donor to acceptor by the tunneling mechanism, by feeling electric atmosphere from protein environment. So far, it was considered that there will be a region through which an electron is likely to be transferred. Usually chemical bonds and so on are considered as its candidate. If it happens, the election tunneling matrix element will not be changed considerably by the thermal fluctuation of protein conformation, because chemical bonds in the protein are not changed by the conformation fluctuation of protein. However, according to the results of our study in which protein conformation fluctuations are realized by the molecular dynamics (MID) simulation and electron tunneling matrix elements are calculated by the quantum chemical theory, electron tunneling matrix element is changed rapidly and greatly by the conformation fluctuation of proteins. As its mechanism, it is considered that
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interference among phases of tunneling currents works significantly. Indeed, it is a very interesting problem how the rapid fluctuation of the value in the electron tunneling matrix element affects the ET rate. We constructed a new non-Condon theory in which we can use the time correlation function of the electron tunneling matrix element obtained by the classical MD simulation. In this theory, the quantum, correction to the nuclear motion is performed and so, the detailed balance condition for the forward and backward rates is satisfied. As a result of analyzing the electron transfer in protein media using this new theory, we found that the energy gap dependence of the ET rate is greatly affected by the rapid fluctuation of the electron tunneling matrix element. Namely; we found that an inelastic tunneling mechanism works at the far normal region and far inverted region and then, the ET rates are much enhanced in both regions. We surveyed the experimental data which support this prediction. Then, we found that the ET rate does not decay appreciably at the very large energy gap in the Rehm-Weller experiment for the fluorescence quenching in polar solution, which is consistent with our theory: Less
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