Review of Electron extended states in proteins
1989-1990. We developed a mathematical formalism to describe polaron states in a two-layer and a three-layer models of a protein globule and calculated electron spectra for the two latter models.
1990-1991. The introduced concept of large-radius extended states offered an all-new look at the problem of long-range electron transfer. Our calculations demonstrated that the radius of the first excited self-consistent state is comparable with the size of the globule, i.e. the whole of the globule takes part in the formation of this state. If the acceptor resides near the globule and the energy of the extended self-consistent state is close to the energy of any electron state of the acceptor, then the view of an electron as belonging to either a donor or an acceptor, not to both, loses its meaning. In the case when the acceptor is far away from the globule, the value of the tunnel matrix element L takes on fundamental significance. For large-radius states the value of L can be several orders of magnitude larger than that for small-radius states.
Analysis of experimental data enabled us to elucidate the role of polarization oscillations of the dielectric continuum. The interaction of an electron with such oscillations may not only be responsible for the electron transfer mechanism, but it can also give birth to the electron state per se to form a state of a new (“polaron”) type. Such states, which have received the name of electron extended states, have been intensively studied in recent years with the globule being simulated by the “dielectric cavity” model. Based on this model, we calculated the probabilities of electron tunneling in a cyt C self-exchange reaction. The calculated values of the reorganization energy, matrix element, distance dependence of the matrix element, and the electron transfer rates are in satisfactory agreement with experimental data. It was shown that the suggested model, despite its “roughness”, adequately describes experimental data on the electron transfer. This gives grounds to believe that the model may be promising for other calculations too.
1991-1992. We calculated and analyzed the main characteristics of electron extended states in a protein globule. For a one-layer and a two-layer models of a “dielectric cavity” we found numerically how the electron ground state energies and the medium reorganization energies depend on the model parameters, such as radii and dielectric permittivities (both static and high-frequency) of the globule. Similar calculations were made for the first extended self-consistent state of a protein molecule. Spectral absorption lines were calculated for the transitions with the greatest oscilation force. Comparison of the calculated spectra with the experimental data on light absorption in azurines led us to conclude that a satisfactory description of the absorption spectra is achieved if we choose the dielectric constant of the internal layer equal to 4 (e=4). We also inferred that an excited azurine macromolecule can show a luminescence band in the near IR-range.
1992-1997. First results were obtained for the electron ground state in a protein globule with off-center position of the metal atom. Spatial distribution of the electron density and the energy of the electron state in a protein were calculated.
1997-1999. Most investigations were centered on modeling a long range electron transfer in proteins and clusters via electron extended states.
1999-2005. A theory was developed and some calculations were performed for electron extended states in chemical and biological systems (proteins, DNA, clusters, liquids). The suitability of the model of electron extended states for the description of electron transfer between proteins was analyzed and the rate of transfer between proteins in aqueous solutions was calculated.