Electron flow through proteins and protein assemblies in the
photosynthetic and respiratory machinery commonly occurs
between metal centers or other redox cofactors that are
separated by relatively large molecular distances, often in the
10−20 A range. To inorganic chemists, such long-distance
electron transfer was a mystery for many years, as we were
accustomed to close-contact models for the transition states of
simple self-exchange reactions between metal ions in aqueous
solution. One of our favorite reactions was the ferrous/ferric
self-exchange, which had been investigated thoroughly by
Richard (Dick) Dodson at the Brookhaven National Laboratory
in the 1940s (and published in Journal of the American Chemical
Society in 1950). Dodson showed that the half-time for this
reaction was on the order of seconds, which he noted was “fast”
but in today’s femtosecond world is very “slow”. Indeed, this
very simple electron transfer, where no bonds are formed or
broken, was found to be orders of magnitude slower than long-distance electron flow through metalloprotein molecules. How could this be?

/pdf/electron-flow-through-metalloproteins-wd69bcpjs4.pdf

Electron flow through metalloproteins.

Electron transfer (ET) processes in proteins drive the energy conversion processes in cells and are also involved in metabolic catalysis. In this tutorial review, the models explaining ET through peptides and proteins are discussed and the biological relevance of ET is elucidated.

Electron transfer in peptides and proteins

We report on a theoretical study of spin-dependent electron transport through single-helical molecules connected by two nonmagnetic electrodes, and explain the experiment of significant spin-selective phenomenon observed in α-helical protein and the contradictory results between the protein and single-stranded DNA. Our results reveal that the α-helical protein is an efficient spin filter and the spin polarization is robust against the disorder. These results are in excellent agreement with recent experiments [Mishra D, et al. (2013) Proc Natl Acad Sci USA 110(37):14872–14876; Gohler B, et al. (2011) Science 331(6019):894–897] and may facilitate engineering of chiral-based spintronic devices.

https://www.pnas.org/content/pnas/111/32/11658.full.pdf

Spin-dependent electron transport in protein-like single-helical molecules

Exposing molecules to ultrashort laser pulses creates electronic wave packets, and therefore, triggers pure electron dynamics in the excited or ionized system. In the case of ionization, these dynamics may manifest as a migration of the initially created localized hole throughout the system and were termed charge migration. Here, we review the theoretical foundation and the most important results obtained in the study of the charge migration phenomenon, as well as give some perspectives for the directions the future studies could go.

http://iopscience.iop.org/article/10.1088/0953-4075/47/12/124002/pdf

Ultrafast correlation-driven electron dynamics

Biological systems often transport charges and reactive processes over substantial distances. Traditional models of chemical kinetics generally do not describe such extreme distal processes. In this Review, an atomistic model for a distal transport of information, which was specifically developed for peptides, is considered. Chemical reactivity is taken as the result of distal effects based on two-step bifunctional kinetics involving unique, very rapid motional properties of peptides in the subpicosecond regime. The bifunctional model suggests highly efficient transport of charge and reactivity in an isolated peptide over a substantial distance; conversely, a very low efficiency in a water environment was found. The model suggests ultrafast transport of charge and reactivity over substantial molecular distances in a peptide environment. Many such domains can be active in a protein.

Sheng Hsien Lin

Papers

Distal charge transport in peptides

Distal Charge Transport in Peptides