The effects of temperature and electrolyte on the redox potential of cytochrome c at a chemically modified microband gold electrode

✍ Scribed by C.X. Cai; H.X. Ju; H.Y. Chen

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 454 KB
• Volume: 40
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(95)00023-8

✦ Synopsis

The dependence of formal potential (F") on temperature for cytochrome c in phosphate buffer solution at various pH was investigated by the microband gold electrode modified with a new promoter 4,6-dimethyl-2-mercaptopyrimidine (DMMP). The temperature dependence of the E"' showed a biphasic character in slightly alkaline solution with a turning point at co. 45°C. However, the E" values decreased monotonically with the increasing temperature in acidic and neutral media. The thermodynamic parameters of the electron transfer reaction for cytochrome c at the chemically modified microband electrode were estimated. The I?" and the changes of standard Gibbs free energy (AC"), entropy (AS") and enthalpy (AH') for the reduction of ferricytochrome c at 25°C and pH 7.0 were 0.272V (vs. NHE), -26.2kJmolF'.

-123.7Jmol-t K-t and -63.1 kJmol-', respectively. The effect of buffer component on the ED' was also studied in binding (phosphate) and nonbinding (Tris/cacodyhc acid) neutral buffer media. The results showed that the E"' in Tris/cacodylic acid buffer solution shifted positively by about IOmV in comparison with that in phosphate buffer solution.