Activation energy, biological electron transfer

Jortner, J., 1976, Temperature dependent activation energy for electron transfer between biological molecules J. Chem. Phys. 64 486034867. 

It is evident that the preceding considerations do not apply to all biological electron transfer systems. Even in the bacterial reaction center, the transfer between the two quinones Qa Qbj which takes place over 18 A [18], is characterized in Rhodobacter sphaeroides by a large entropic contribution, which has been attributed to the high solvent exposure of Qg [126]. By using the activation energy value reported in Ref. [126], two very different X values may be deduced from Eq. (23) = 0.1 eV and Aj = 2.5 eV. The previous considerations... 

In recent years considerable effort has been devoted to elucidating the pathway of energy transfer in supramolecular assemblies. The impetus for this work stems from the fact that electron transfer reactions are endemic in biosynthesis. Such critical and well-known cellular activities as respiratory oxidative phosphorylation and photosynthesis " rely on electron transfer processes. Most of these are mediated via protein-protein interactions. Currently, it remains uncertain whether a specific pathway is required for a given biological electron transfer event The study of synthetic donor-acceptor sys-... 

By observation and better understanding of these sophisticated biological processes, the design of multiporphyrinic species capable of performing energy and electron transfer has been both stimulated and facilitated, leading to one of the major areas of research in molecular electronics in terms of activity and publications. In terms of applicability, the synthetic systems face two challenges. 

Guergova-Kuras, M., Boudreaux, B., Joliot, A., JoHot, R, and Redding, K., Evidence for two active branches for electron transfer in photosystem 1, Proc. Natl. Acad. Sci. U.S.A., 98, 4437, 2001. Nitschke, W, Mattioli, T., and Rutherford, A.W., The FeS-type photosystems and the evolution of photosynthetic reaction centers, in Origin and Evolution of Biological Energy Conversion, Baltscheff-sky, H., Ed., VCH Publishers, Weinheim, Germany, 1994, chap. 7. 

---