The stoichiometry of creation of membrane lesions by hematoporphyrin derivative and light

Photohemolysis is induced by photodynamic treatment of human erythrocytes using the sensitizer hematoporphyrin derivative (HPD). Photohemolytic rate is found to vary with the square of HPD concentration and with the square of the fluence. The results imply that creation of a discrete lysis-promoting lesion in the red blood cell membrane requires the action of two photons and two HPD molecules. The results must be considered in attempts to model HPD photosensitization effects.