Electrochemical approach to the mechanism of urea denaturation of horse heart cytochrome c

The effect of urea denaturation on the electroactivity of horse heart cytochrome c has been studied by differential pulse polarography and cyclic voltammetry at a gold electrode; the gold electrode was activated by 4,4'-bipyridine. Essentially, two redox couples with E₀₁ ≈ 0.25 V and E'_oz ≈ ?0.05 V (vs. normal hydrogen electrode) have been detected. The experimental results have been interpreted on the basis of the existence of equilibria between native and denatured electroactive forms; transitory species have been assumed to appear on reduction. The scheme that we have proposed agrees well with the conclusions obtained previously by other authors on conformational changes. Moreover, the advantage of electrochemical techniques in investigating the denaturation process has been underlined.