Porphyrin-Membrane Interactions: Structural, Kinetic and Thermodynamic Aspects Studied Using Fluorescence Techniques

“Haematoporphyrin derivative” (HPD) is being used increasingly in the photochemical treatment of malignant tumours. Its mode of action has yet to be elucidated. It is believed that the exposure of HPD to red light results in the production of singlet oxygen which reacts with surrounding bimolecules and kills the cell.1 The primary site of action is thought to be at the membrane surfaces,2 where porphyrins collect at hydrophobic loci3 and catalyse the cross-linking of membrane proteins4,5 which leads to cellular necrosis, liie have investigated the structural, kinetic and thermodynamic aspects of HPD association with synthetic membranes as an aid to understanding its efficacy in photo-irradiation therapy. Protoporphyrin (PP) and haematoporphyrin (HP) have also been examined, and the results are presented here for comparison.