Protein Dynamics and Electron Transfer: Electronic Decoherence and Non-Condon Effects

• Published in: Proceedings of the National Academy of Sciences - PNAS 2005-03, Vol.102 (10), p.3552-3557
• Main Authors: Skourtis, Spiros S., Balabin, Ilya A., Kawatsu, Tsutomu, Beratan, David N., Gray, Harry B.
• Format: Article
• Language: English
• Subjects: Approximation; Autocorrelation; Azurin - chemistry; Biological Sciences; Biophysics; Chemical valence; Chemistry; Correlation analysis; Electron transfer; Electron Transport; Electron tunneling; Errors in statistics; Hydrogen bonds; Long-Range Electron Transfer Special Feature; Models, Molecular; Molecules; Physical Sciences; Proteins; Trajectories; Vibration
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0409047102

We compute the autocorrelation function of the donor-acceptor tunneling matrix element$\langle T_{DA}(t)T_{DA}(0)\rangle $for six Ru-azurin derivatives. Comparison of this decay time to the decay time of the time-dependent Franck-Condon factor {computed by Rossky and coworkers [Lockwood, D. M., Cheng, Y.-K. & Rossky, P.J. (2001) Chem. Phys. Lett. 345, 159-165]} reveals the extent to which non-Condon effects influence the electron-transfer rate.$\langle T_{DA}(t)T_{DA}(0)\rangle $is studied as a function of donor-acceptor distance, tunneling pathway structure, tunneling energy, and temperature to explore the structural and dynamical origins of non-Condon effects. For azurin, the correlation function is remarkably insensitive to tunneling pathway structure. The decay time is only slightly shorter than it is for solvent-mediated electron transfer in small organic molecules and originates, largely, from fluctuations of valence angles rather than bond lengths.