Figure 5

Midpoint potential measurement of HLMW b ₅ with spectroelectrochemical titration. Spectroelectrochemical titration was conducted by recording the absorption spectrum of HLMWb₅ (15 μM in 50 mM sodium phosphate buffer pH 7.0) at various redox potentials by the addition of sodium dithionite to the oxidized form at 25°C in the presence of various redox mediators (for detail, see main text). Least-square curve-fitting of the spectroelectrochemical titration data by using the Nernst equation assuming a single redox component. Solid circles indicate data points for the reductive phase and + for the oxidative phase. Other conditions are indicated in the main text.