Major differences in oxysterol formation in human low density lipoproteins (LDLs) oxidized by *OH/O2*- free radicals or by copper.

The aim of our study was to determine the oxysterol formation in low density lipoproteins (LDLs) oxidized by defined oxygen free radicals (*OH/O2*-). This was compared to the oxysterol produced upon the classical copper oxidation procedure. The results showed a markedly lower formation of oxysterols induced by *OH/O2*- free radicals than by copper and thus suggested a poor ability of these radicals to initiate cholesterol oxidation in LDLs. Moreover, the molecular species of cholesteryl ester hydroperoxides produced by LDL copper oxidation seemed more labile than those formed upon *OH/O2*(-)-induced oxidation, probably due to their degradation by reaction with copper ions.