AVS 45th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoM

Paper BI-MoM11
Electron Transfer of Cytochrome c on Lipid-Coated Graphite Electrode

Monday, November 2, 1998, 11:40 am, Room 326

Session: Protein Solid-Surface Interactions
Presenter: S. Boussaad, Florida International University
Authors: S. Boussaad, Florida International University
R. Arechabaleta, Florida International University
N.J. Tao, Florida International University
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The structural and electron transfer properties of Cytochrome c (Cyt c) Langmuir-Blodgett (LB) films, and Cyt c on Cardiolipin (CL) and Phosphatidylcholine (PC) monolayers have been studied on graphite electrode with tapping mode atomic force microscopy (AFM) and cyclic voltammetry. The protein in the LB film forms an ordered structure and exhibits a reversible electron transfer reaction in phosphate buffer. The analysis of the AFM images reveals a quasi-hexagonal structure with a=4.4 ± 0.2 nm, b=5.3 ± 0.2 nm and @gamma@=71 ± 3°. These dimensions are in good agreement with the X-ray data. The redox peaks of the Cyt c monolayer are about 80 mV more positive than those of the spontaneously adsorbed protein, and the electron transfer rate (20-30 s@super -1@) is smaller than 60-80 s@super -1@, the value for the adsorbed Cyt c. Furthermore, both monolayers of CL and PC are ordered on graphite, but their interactions with Cyt c are quite different. On CL monolayer, Cyt c adsorbs spontaneously and the adsorbed protein preserves the electron transfer reaction. In addition, the protein disrupts seriously the ordered structure of the lipid monolayer. However, on PC monolayer, Cyt c does not adsorb. This difference is consistent with the fact the CL plays an important role in the activity of Cyt c oxidase than PC.