STUDIES ON THE ELECTRODE PROCESS THERMODY NAMICS OF CYTOCHROME-C AT AMICROBAND GOLD ELECTRODE MODIFIED WITH 4,6-DIMETHYL-2-MERCAPTOPYRIMIDINE

The redox thermodynamics of cytochrome C at a 4,6-dimethyl-2-mercaptop yrimidine (DMMP), a new electron transfer promoter of cytochrome C, mo dified microband gold electrode (DMMP/Au) was investigated by cyclic v oltammetry. The thermodynamic parameters of the electron-transfer reac tion of cytochrome C at DMMP/Au electrode were estimated, The normal p otential E(0'), the changes of entropy, enthalpy and Gibbs free energy , Delta S-0 , Delta H-0 and Delta G(0), for cytochrome C at 25 degrees C and pH 7.0 were 0.272 V (vs, NHE), -123.7 J . mol(-1). K-1, -63.1 k J . mol(-1) and -26.2 kJ . mol(-1), respectively, The effects of tempe rature and pH on the thermodynamic parameters of cytochrome C were dis cussed, The E(0') vs, T plot shows remarkable biphasic character in an alkaline solution with a turning point at ca. 45 degrees C, whereas i n an acid or neutral solution the E(0') values changed monotonically w ith temperature.