title: Determination of the redox potential and diffusion coefficient of the protein plastocyanin using optically transparent filar electrodes.
abstract: Direct and mediated electrolysis of the protein plastocyanin at a gold filar electrode is described. The filar electrode used is of a unique design that allows potentiometric measurements, steady-state voltammetry and absorption spectrophotometry to be performed on a few microliters of solution containing 0.1-1.0 mM protein. As a result, we have determined the formal potential and diffusion coefficient of the blue copper protein, plastocyanin, to be 372 +/- 5 mV vs. normal hydrogen electrode and 8.9 X 10(-7) cm2 X s-1, respectively. The same value of the formal potential is obtained from a steady-state current experiment, an equilibrium spectrophotometric experiment, and a twin-electrode steady-state spectrophotometric experiment. The fact that the diffusion coefficient is measured under conditions of steady-state current, results in significant improvement in signal to background over techniques that monitor a transient current, while the potential is changing.
mesh_terms: D004563:Electrochemistry; D004566:Electrodes; D008433:Mathematics; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000378:metabolism*; D010970:Plastocyanin / Q000378:metabolism*; D011199:Potentiometry
chemical_list: D010940:Plant Proteins; D010970:Plastocyanin