Interfacial redox processes of cytochrome b562

Area of Science:

• Electrochemistry
• Biophysics
• Surface Science

Background:

• Cytochrome b(562), an anionic heme protein, is crucial for electron transfer processes.
• Understanding protein-electrode interfaces is key for biosensor and bioelectronic applications.

Purpose of the Study:

• To investigate the structure, redox equilibria, and electron transfer dynamics of electrostatically immobilized cytochrome b(562).
• To compare the behavior of cytochrome b(562) with cytochrome c at different electrode interfaces.

Main Methods:

• Electrostatic immobilization of cytochrome b(562) on amino-terminated self-assembled monolayers on Ag electrodes.
• Stationary and time-resolved surface-enhanced resonance Raman spectroscopy (SERRS).
• Cyclic voltammetry (CV) for interfacial redox process analysis.

Main Results:

• Heme pocket structure and redox equilibria of immobilized cytochrome b(562) were characterized.
• Electron transfer dynamics showed limited dependence on monolayer thickness, suggesting tunneling is not rate-limiting.
• Comparison with cytochrome c revealed differences attributed to interfacial electric fields and protein orientation.

Conclusions:

• Interfacial electric fields significantly influence protein conformational and redox equilibria.
• Cytochrome b(562) electron transfer is not primarily gated by protein re-orientation.
• Interplay between interprotein and heterogeneous electron transfer likely governs electron exchange rates.