Fig. 8.
Proposed two step mechanism for electron transfer from NADH to quinone in Complex I (A), in presence of Class A inhibitors (B) and in presence of Class B inhibitors (C). The role of hydrophilic (CoQ1) and hydrophobic (DB) quinones is highlighted. CoQ1 can react with the physiological ubiquinone reducing site and, because of its higher water solubility, it can also react with the electron escape site, increasing superoxide production.