Theoretical study on the electronic structure of [4Fe-4S] cluster

The electronic structures and magnetic interactions of [4Fe-4S] cluster in the oxidized state of high-potential iron-sulfur protein (HiPIP) were studied by using density functional theory method (DFT) with the broken symmetry (BS) approach. The analyses of the mixed-valence states were performed within a spin Hamiltonian defined as a Heisenberg exchange (J) term and a double exchange (B) term. Each interaction (Jand B values) was evaluated from the BS-DFT calculations. Natural orbital analysis was employed to investigate the nature of the chemical bonds and magnetic orbitals of the [4Fe-4S] cluster. It was shown that derealization of the odd electron (extra electron) depended on the spin states because of its strong antiferromagnetic couplings between iron centers.