Adsorption of Microperoxidase-11 in Vertical Silica Mesochannels and Electrochemical Investigation of Its Electron Transfer Properties

Abstract

Microperoxidase-11 (MP-11) is an excellent model for hemoproteins such as cytochrome c. In this work, we report the adsorption of MP-11 onto silica mesochannels (SMCs) vertically attached to the indium tin oxide (ITO) electrode surface via the electrostatic attraction. Given the diameter of SMCs (2∼3nm) is comparable to the molecular dimension of MP-11 (1.1×1.7×3.3nm), only its monomeric form was selectively adsorbed by SMCs, as revealed by the UV-visible spectroscopy measurements. The cyclic voltammgram of adsorbed MP-11 molecules showed that the peak current was linearly dependent on the scan rate, suggesting the occurrence of a surface controlled process. And thus estimated surface coverage was indicative of adsorption of multiple MP-11 molecules in a SMC. We inferred that the electron transfer reaction is kinetically limited by the electron communication between MP-11 molecules adjacent to the electrode and the electrode. The rate constant was estimated to be 8.3s−1.