Received: August 24, 2007

In Final Form: October 18, 2007

Abstract:

This work uses cytochrome c, an electron carrier in the respiratory chain, as a model to probe how surface adsorption affects the folding of a protein. The electrochemical activities of the protein horse heart cytochrome c is studied under conditions where it is covalently attached onto a mixed carboxylic acid and hydroxyl-terminated SAM, which covers a Au electrode's surface. Changing the pH of the electrochemical buffer solution changes the conformation of the cytochrome c and causes a change of the peak currents in cyclic voltammetry and a shift of the peak potential. In addition, the unfolded cytochrome c displays peroxidase activity; the apparent Michaelis-Menten constant K_m for cytochrome c at these surfaces has been determined to be 7.9 mM at pH 3 and 144.3 mM at pH 7.

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