Electrochemistry of Oriented Cytochrome c Monolayer on Modified Gold Electrode and Its in Situ Denaturation in Organic/Aqueous Medium

Cytochrome c (Cyt c) was absorbed on gold electrode modified with a mixture (1:3) of 11-mercapto-1-undecanol and 11-mercaptoundecanoic acid (C11) solutions. The Cyt c/C11/Au electrode thus prepared showed a well-defined quasi reversible voltammetric peak with electron transfer rate constant of 234 s-1. The surface coverage of Cyt c oriented on the surface of C11-modified electrode was determined to be 4.73×10-11 mol cm-2. The Cyt c/C11/Au electrode linearly responded to H2O2 in the concentration range from 90 to 500 ?M with a correlation coefficient of 0.9973. Using the reciprocal plot of the steady state current versus hydrogen peroxide concentration, apparent Michaelis constant for the Cyt c was estimated to be 759 ?M. In addition, voltammetric analysis was used to study the in situ denaturation of the immobilized Cyt c by gradual addition of either urea up to 8 M or dimethyl formamide (DMF) up to 55%. It was revealed that the mechanism of Cyt c denaturation depends on media (organic or aqueous) were used. So that in the presence of DMF it follows a two-phase process, whereas in urea containing buffer solution, it pursues a single-phase course.