The reorganization energy of azurin in bulk solution and in the electrochemical scanning tunneling microscopy setup.

The total reorganization energy lambda of azurin is theoretically studied both for the electron self-exchange reaction and for the protein in the electrochemical scanning tunneling microscopy (ECSTM) setup. The results demonstrate the importance of the proximity between the active sites in the encounter complex to reduce lambda for the electron self-exchange reaction and quantifies the effects of the presence of an STM environment (tip and substrate) on lambda. A comparison of the calculated results with experimental data is performed, and the relative magnitudes of the inner and outer contributions to lambda are discussed.