Vincent W. Bowry

Inverse deuterium kinetic isotope effect for peroxidation in human low-density lipoprotein (LDL): a simple test for tocopherol-mediated peroxidation of LDL lipids

α‐Tocopherol (α‐TOH) can act as a pro‐ or anti‐oxidant for isolated ubiquinol‐10‐free human low density lipoprotein (LDL). We demonstrate that α‐TOH is a more potent pro‐oxidant than other forms of vitamin E for LDL peroxidation initiated by mild fluxes of aqueous peroxyl radicals and low concentrations of Cu2+. A simple deuterium exchange test shows that α‐TOH switches from pro‐ to anti‐oxidant at Cu2+: LDL ratios 2.5. The results suggest that this test may be useful to distinguish ‘inhibited’ perioxidation of emulsion lipids propagated via the lipid peroxyl radical from that mediated via the antioxidant radical.

Evidence for reversible ring-opening of the α-cyclopropylbenzyl radical

Kinetic absorption spectroscopy, EPR, and tributyistannane product data indicate that the α-cyclopropylbenzyl radical (1a) undergoes reversible ring-opening to the 4-phenylbut-3-enyl radical (2a) and that equilibrium favours the ring-closed form, (1a).