Study on the electrochemical behaviour of cytochrome C at the gold electrode modified with 4-hydroxy-6-methyl-2-mercaptopyrimidine

Abstract

The reduction and oxidation of cytochrome C at the gold electrode modified with 4-hydroxy-6-methyl-2- mercaptopyrimidine (HMMP) has been investigated by cyclic voltammetry. It has been demonstrated that HMMP is an effective and stable promoter. The thermodynamic parameters of the electron-transfer reaction of cytochrome C at HMMPI/Au , electrode have been estimated in phosphate buffer solution containing 0.1 mol L^-I NaCIO₄. The normal potential <em>E</em>^o, the changes in entropy (∆<em>S</em>^o) enthalpy (∆<em>H</em>^o) and Gibb~ r:fnergy (∆<em>G</em>^o) for :1'tochrorrle C at 20&deg;C and <em>p</em>H 7.0 have been found to be 0.267 V(vs. NHE), - 52.7 J mol^-1K^-1,- 41.25 kJ mol and -25.8 kJ mol^-1 , respectively. The temperature dependence of the formal redox potential &pound;'" obtained in the temperature range of 5- 60&deg;C shows remarkable biphasic character in an alkaline solution with a turning point at 45&deg;C whereas. in an acid or neutral solution the E^o, values change monotonically with temperature which may be attributed to a structural change in the protein moiety of the cytochrome C in alkaline solution.