MECHANISMS OF ENZYMATIC REACTIONS - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 55

octahedral symmetry of the complexes, the orbitals and of the subshell
interact mainly with orbitals of ligands. Meanwhile, the networks, which start as a
will not participate much in the superexchange coupling under this consideration.
The Fig.2.11 shows, that good correlation between theoretical and experimental
electron coupling matrix elements takes place when orbitals of Fe and orbitals of
Ru are involved in the ET process. The general tendency is to have coupling markedly
stronger for His39 than for His62, although the distance between the donor and acceptor is
approximately the same. When effective s-orbitals are localized on metals and, therefore,
mostly s-paths contribute in the coupling, a drastic difference between theoretical and
experimental values of electronic coupling has been found. This observation clearly
demonstrates the importance of symmetry and stereochemical effects in long-range
electron transfer.
2.3. Hydrogen transfer
Many enzymatic reactions involve transfer protons, hydrides or hydrogen atoms
(Alhambra et al., 2000; Allison, 1998;; Backgren et al., 2000; Blum et al., 2001; Cha et al.,