Oxidizability of cardiac cardiolipin in Triton X-100 micelles as determined by using a Clark electrode

The kinetics of the chain free-radical oxidation of cardiolipin (CL), a unique phospholipid containing four linoleate moieties, have been studied for the first time. The technique based on monitoring oxygen consumption by using a Clark electrode was applied to determine the oxidizability of CL during its initiated oxidation in aqueous Triton X-100 micelles in 50 mM phosphate buffer, pH 7.40, at 37 °C. The oxidizability was characterized by the k2/2k3 ratio, where k2 and k3 are the rate constants for the reaction of chain propagation (LO2 + LH → LOOH + L) and chain termination (2LO2 → products), correspondingly. The oxidizability of CL (in M−0.5 s−0.5) was found to be of 0.62 ± 0.07 (calculated on the basis of a single linoleate fragment) that is twice as much than the oxidizability of methyl linoleate (0.32 ± 0.04) determined in the same testing systems. It has been shown that the increase in k2/2k3 by a factor of two when going from the oxidation of ML to that of CL is almost completely determined by the increase in k2.