Abstract—Lipid model membrane systems, liposomes, may be oxidized by both toluidine blue Osensitized photo‐oxidation and radiofrequency‐discharge‐generated singiet oxygen. Oxidation can be followed by the appearance of lipid peroxides, malondialdehyde formation, and ultimately by the lysis of the liposomes. Inhibition of oxidation is observed in both systems using either β‐carotene or DABCO. These observations are consistent with the view that type II (singlet oxygen) reactions are involved in this photodynamic system.

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Guanosine-2JC and guano~ine-8-~Y3 were subjected, under similar environmental conditions, to oxidation either by radiofrequency-discharge-generated singlet oxygen or by a methyleneblue-sensitized photodynamic reaction. The reaction products in both cases were compared chromatographically. The product distributions were not identical, indicating differing modes of oxidation in these two systems. It is suggested that both Type I and Type I1 oxidation mechanisms are operative in the photodynamic system, whereas only Type 11-like reactions occur in the radio-frequency-discharge system.