We present a cluster model for the active site of oxidized azurin, and investigate the electronic structure of the active site of oxidized azurin by using density functional calculations with polarizable continuum model. The singly occupied molecular orbital (SOMO) and spin density in the model widely distribute around the Cu 3d x 2 −y 2 and S(Cys112) 3p orbitals. The dependency of electronic properties such as partial charge density and spin density on the dielectric constant is discussed. We find that partial spin density and charge density on the copper ion become larger, when the dielectric constant increases.

ABSTRACT:We present two cluster models of the active site of azurin. These models are determined by two stable configurations during our molecular dynamics (MD) simulation. In MD simulation, we find two stable configurations connected by the "jump motion" of Met121. One configuration is similar to the crystal structure by X-ray analysis, and the other is not the same. We perform density functional calculations for these two models and investigate physical properties such as total energy, singly occupied molecular orbital (SOMO), and spin density for each model. We find the difference in the shape of SOMO each other. We also estimate the reduction potential for each model and discuss the reduction potential and solvent effect of each model in relation to the electron transfer, which is one of the functionality of azurin.

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