Electronic structure and magnetism at the active site in ferredoxin: Ab initio approach to (Fe2S2)2+ complex with the 1st peptide shell

We have studied the iron–sulfur cluster systems which model an active site of ferredoxin proteins by using the first-principles electronic structure calculation. The modeled molecule is a complex between the (Fe2S2)2+ core and the amino acid residues which surround the core. The electronic structure of oxidized state for the molecules is presented. The antiferromagentic arrangement for Fe atomic magnetizations was obtained as the ground state. The spin polarized state of the half-filled Fe 3d orbitals is consistent with the formal valence of Fe3+. The induced spin density on the cysteine S atoms was found to be parallel to the direction of magnetization on the nearest Fe atom. The hybridized states consisting of N 2p and C 2p orbitals at the side chain of Arg residue appeared just above the highest occupied molecular orbital level for the free standing peptide.

The iron–sulfur cluster systems which model an active site of ferredoxine proteins have been studied with using the first priciples electronic structure calculation. We modeled them as a complex of the (Fe2S2)2+ core and the 1st shell of amino acid residues. The hybridized orbitals consisting of N 2p and C 2p orbitals in the side chain of Arg residue locates just above the HOMO level for the cluster without having the salt bridge.Figure optionsDownload as PowerPoint slide