Biomimetics Bradyrhizobium japonicum Catalytic activities Coordination reactions Cyclic voltammetry Energy transductions Enzyme activity Enzymes Hemoglobin Immobilized enzymes In-situ Lipid bilayers Nanostructured Native structures Oxygen Porphyrins Reduction potentials Silver Silver electrodes Spectroelectrochemical studies Spectroelectrochemical titrations Spectroelectrochemistry Volumetric analysis