Defense Date


Document Type


Degree Name

Doctor of Philosophy



First Advisor

Fred M. Hawkridge


Direct heterogeneous electron transfer reactions between horse heart cytochrome g_and silver electrodes were investigated by electrochemical and spectroelectrochemical methods. The kinetics of these reactions were established as being quasi-reversible, with a formal heterogeneous rate constant (k°'s,h) ranging between 0.18 - 1.5 x 10-3 cm/s, for both polished and electrochemically roughened silver surfaces. Such reactions were stable and reproducible for over ten hours at room temperature. These results clearly demonstrate that neither electrode surface modification nor the inclusion of mediators is necessary to study electron transfer reactions of heme proteins at metal electrodes.

A crucial factor in obtaining the quasi-reversible heterogeneous electron transfer kinetics described above is the use of highly purified, never lyophilized, cytochrome c samples. When samples were lyophilized after purification, irreversible electron transfer kinetics were observed. These results show the profound negative impact that lyophilization has on the rates of electron transfer at bare metal electrodes. The lyophilization process was indicated to produce small amounts of oligomeric material which rapidly and irreversibly absorbs on the electrode surface preventing further solution cytochrome c molecules from reacting. This denatured form, along with other solution impurities, is believed to be the reason for the lack of stable facile responses towards metal electrodes.

Surface enhanced resonance Raman spectroscopy was used to monitor conformational changes associated with the direct electron transfer reactions of purified cytochrome c at silver electrodes. The results of this study indicated that cytochrome c exists in a penta-coordinate high spin configuration, with a formal potential =0.350 volts more negative than its corresponding bulk solution value when adsorbed. This suggests that cytochrome c is still capable of exchanging electrons in a quasi-reversible fashion even though there is strong irreversible adsorption of a denatured form on the electrode surface.


Scanned, with permission from the author, from the original print version, which resides in University Archives.


© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission


Included in

Chemistry Commons