Ma. Cubillos et al., Kinetics of lipid peroxidation in compartmentalized systems initiated by awater-soluble free radical source, CHEM PHYS L, 104(1), 2000, pp. 49-56
Kinetic rate Laws arising from theoretical expectations for the oxidation o
f lipids initiated by water-soluble free radicals in compartmentalized syst
ems under different experimental conditions are deduced. In particular, the
predictions for the kinetic reaction orders in: (a) intra-particle oxidiza
ble compound concentration (at fixed number of particles and particle size)
, alpha; (b) number of particles or analytical lipid concentration (at fixe
d intra-particle concentration and particle size), beta and (c) initiator,
gamma, are obtained. The reaction orders beta and gamma are determined by t
he fraction of initiator derived radicals captured by the particles (f) and
the mean number of chain carrying radicals per particle ([n]) when the sys
tem reaches the steady state condition. Predicted orders in initiator range
from 0 ([n] = 0.5) to 0.5 (f --> I; [n] > > 1), while the order in number
of particles ranges between 0.5 (f -->, 1; [n] > > 1) and 1. These predicti
ons are tested by measuring the kinetic law for the oxidation of SUV's egg
yolk phosphatidylcholine vesicles initiated by the thermal decomposition of
ABAP. The results indicate that, under the conditions employed, beta = 0.6
8 +/- 0.05 and gamma = 0.46 +/- 0.04. These values are close to those expec
ted for a system in which [n] > > 1 and the efficiency of capture is relati
vely high. This last condition is confirmed by estimating the efficiency of
capture from a comparison of induction times elicited by similar concentra
tions of Trolox and alpha-tocopherol. (C) 2000 Elsevier Science Ireland Ltd
. All rights reserved.