Interaction of the meso-tetrakis (4-N-methylpyridyl) porphyrin with gel and liquid state phospholipid vesicles

► Vesicle surface charge and physical state both affect the porphyrin partitioning into membrane phases. ► The porphyrin affinity is higher in vesicles that carry a negative surface charge. ► The cationic porphyrin is preferentially located in the Stern layer of the vesicles. ► Zeta potential measurements show only partial neutralization of the vesicle surface charge by the porphyrin.