Effect of N-alkyl-N,N,N-trimethylamonium bromides on the auto-peroxidation of egg yolk phosphatidylcholine in liposomes.

N-alkyl-N,N,N-trimethylamonium bromides (cnTMA, n = number of carbons in alkyl) stimulate and inhibit the autoperoxidation of egg yolk phosphatidylcholine (EYPC) in liposomes at n less than 12 and n greater than 12, respectively, with maximum stimulation for n = 8. CnTMA intercalate between EYPC molecules (decreasing the yield of ROO. + RH----ROOH+R. reaction, where RH is an unsaturated EYPC acyl chain, R. - EYPC acyl radical, and ROO. - peroxy radical of the EYPC acyl chain) and disorder the hydrophobic region of the bilayer (increasing the oxygen solubility there and thus yield of R. + O2----ROO. reaction). The final level of oxidation is affected by a summation of the EYPC lateral separation and disordering effects.