Hydrodynamic Effects in the Photosensitized Lysis of Liposomes*

The photosensitized lysis of phosphatidylcholine liposomes incorporating methylene blue in the membrane or in the presence of external methylene blue is promoted by hydrodynamic agitation concurrent with or subsequent to irradiation with red light. The results implicate the attack of singlet oxygen on an unsaturated lipid component as the key photochemical step, which is followed by additional membrane damage induced by hydrodynamic action.