Reactions of Radicals with Lecithin Bilayers

The kinetics of reaction of •OH and e_ aq⁻ with lecithin bilayers have been measured. The rate for •OH + lecithin is 5.1± 0.9× 10⁸ M⁻¹ sec⁻¹ while the e_ aq⁻ + lecithin rate is very slow. When a solute such as pyrene is solubilized in the bilayer, •OH and e_ aq⁻ may react with the solute; rates of 1.65± 0.12× 10⁹ M⁻¹ sec⁻¹ and 7× 10⁷ M⁻¹ sec⁻¹ have been measured for reaction of •OH and e_ aq⁻ , respectively, with pyrene in lecithin. These rates are lower than those observed for similar reactions in homogeneous systems. This is explained in terms of (a) the protective effect of the bilayer, this being especially true for e_ aq⁻ which does not readily leave the aqueous phase, and (b) in ter...