Theoretical studies on the magnetic interaction and reversible dioxygen binding of the active site in hemocyanin

We have investigated the magnetic interaction, the shape of the whole poten tial energy surface, and the electronic structure of realistic models of th e active site in hemocyanin for the reversible dioxygen binding by UHF and DFT calculations. The results are discussed in relation to the effective ex change integrals and the charge and spin density distributions as well as t he shape and symmetry of natural orbitals. The superexchange interaction vi a bridging dioxygen accounts for the strong antiferromagnetic interaction b etween the two copper ions. The shapes of the potential energy curve sugges t that the structural change of hemocyanin controls dioxygen binding. (C) 2 001 Elsevier Science B.V. All rights reserved.