Oxidation-Induced Spin Probes In Low-Density Lipoproteins

PBN trapping indicated the presence of at least two types of radicals induced in LDL upon slow oxidation, as observed with EPR spectroscopy. The EPR spectra are very similar to those of the spin probes or spin labels, which are routinely used in the studies of macromolecular systems and supramolecular assemblies. The parameters of the spectral line shapes, treated in two different theoretical models, did not provide conclusive evidence for the phase transition in the LDL particles, known to be present at about 25 degreesC. It is concluded that both types of trapped radicals, or at least one of them, are associated with the apolipoproteins, with the spin probe sticking into the lipid domain of phospholipids.