Using Functional Models to Understand the Four-Electron Reduction of Dioxygen by Cytochrome c Oxidase Under Steady State Conditions

Abstract

A new functional biomimetic model of cytochrome c oxidase is reported. It is synthesized in 32 steps. Single turnover reaction with oxygen leads to the same intermediates as the ones reported in the enzyme: Fe(III)O₂^·-/Cu(I)/PhOH (oxygen complex), and Fe(IV)=O/Cu(II)/PhO^· (PM). A sister model derivatized with an alkyne was immobilized on azide-functionnalized self-assembled monolayer (SAM) coated gold electrodes by Cu(I)-catalyzed click chemistry. The rate of electron transfer from the electrode to the model was controlled by the length of the linker in the SAM. Steady-state turnover was achieved at biologically relevant electron transfer, where CuB and Tyr244 mimics rapidly deliver their electrons, hence minimizing the release of partially reduced oxygen species (PROS).