    2.8.1.8 | [4Fe-4S]-center |
the ground state of the two FeS clusters, both in the [4Fe4S]2+ oxidation state, is a singlet state with antiferromagnetically coupled high-spin Fe ions. There is a large variation of the energies of the various broken-symmetry states, up to 40 kJ/mol. For the two S-insertion reactions, the highest energy barrier is found for the hydrogen-atom abstraction from the octanoyl substrate by 5'-dA radical. The formation of 5'-dA radical shows an energy barrier of 6 kJ/mol for the first S-insertion reaction and no barrier for the second S-insertion reaction. Thehe first S ion attack on the C6 radical of octanoyl takes place directly by the transfer of the H6 from the substrate to 5'-dA radical, whereas for the second S-insertion reaction, a C8 radical intermediate is formed with a rate-limiting barrier of 71 kJ/mol |
761530 |
