Determination of a representative formal redox potential of the Fe(II)/Fe(III) redox couple in cyanhaemoglobin, at pH = 7 and related to the state in solution, was the objective of this work. It was achieved at low concentrations of the protein (5 μM) to circumvent undesired adsorption. Square-wave voltammetry instead of classical cyclic voltammetry was applied because this method is more sensitive and provides information on the formal redox potential and reversibility, even for rapid processes. We obtained E°′ = − 0.12 ± 0.01 V for cyanhaemoglobin and E°′ = − 0.10 ± 0.01 V, vs. SHE, for myoglobin in comparison. These values differ by only 20 mV because the two Fe(II)/Fe(III) redox centres are embedded in closely resembling chemical environments. The small difference is probably owed to the additional axially coordinating cyanide ligand in cyanmethaemoglobin which slightly favours the Fe(III) state in the haem macrocycle.

这项工作的目的是测定在pH = 7且与溶液状态有关的氰化血红蛋白中的Fe（II）/ Fe（III）氧化还原对的代表性形式氧化还原电势。在低浓度的蛋白质（5μM）下可以避免不希望的吸附。使用方波伏安法代替经典的循环伏安法，因为这种方法更灵敏，即使在快速过程中，也能提供有关形式氧化还原电势和可逆性的信息。对于氰化血红蛋白和E°，我们获得E° '= − 0.12±0.01 V相对于SHE，肌红蛋白的′= − 0.10±0.01 V. 这些值相差仅20 mV，因为两个Fe（II）/ Fe（III）氧化还原中心嵌入在非常相似的化学环境中。较小的差异可能归因于在氰化高铁血红蛋白中额外的轴向配位氰化物配体，它在血红素大环中略微偏爱Fe（III）态。