DETERMINATION OF THE MOLAR ABSORPTION-COEFFICIENTS OF C-TYPE CYTOCHROMES USING OPTICALLY TRANSPARENT THIN-LAYER ELECTRODES

The simultaneous monitoring of both the absorbance and charge consumed in electrolysis in a precalibrated Optically Transparent Thin-Layer Electrode (OTTLE) cell was demonstrated as a precise method for determining the molar absorption coefficients of electron-transfer proteins. In this method, the procedure for a direct determination of the concentration of the protein could be omitted. The values of the molar absorption coefficients of c-type cytochromes at the alpha-peaks of reduced forms were determined by this method: 28.4 mM-1 cm-1 (1 M = 1 mol dm-3) at 550 nm for horse heart cytochrome c, 119 mM-1 cm-1 at 552 nm for cytochrome c3 from Desulfovibrio vulgaris, Miyazaki F, and 116 mM-1 cm-1 at 552 nm for cytochrome c3 from Desulfovibrio vulgaris, Hildenborough.