Respiratory chain inhibition by fullerene derivatives: Hydrogen peroxide production caused by fullerene derivatives and a respiratory chain system

Fullerene is a new type of carbon allotrope. We have shown that the fullerene derivative C₆₀-bis(N,N-dimethylpyrrolidinium iodide), a regio isomer mixture, inhibited Escherichia coli growth and dioxygen uptake caused by E. coli and glucose. This result indicates that the mechanism of the bacteriostatic effect is the inhibition of energy metabolism. In this study, we isolated two regio isomers of C₆₀-bis(N,N-dimethylpyrrolidinium iodide) and studied their effect on E. coli growth and on respiratory chain activity. In dioxygen uptake caused by the inner-membrane and NADH, the effect of fullerene derivatives was biphasic. At low concentrations of both fullerene derivatives, dioxygen uptake was inhibited, whereas at high concentrations, it was increased. At high concentrations, consumed dioxygen was converted to H₂O₂. An electrochemical study revealed that reduced fullerene derivatives react with dioxygen. This activity was closely related to a redox property of the isomers.