Kinetics of incorporation of porphyrins into small unilamellar vesicles.

The kinetics of hematoporphyrin or deuteroporphyrin incorporation in egg phosphatidylcholine small unilamellar vesicles have been investigated by fluorescence stopped-flow measurements. The processes can be described by a fast equilibrium. The on-rate constant is nearly diffusion controlled regardless of the compound used and the pH. The affinity of these porphyrins for the vesicles is merely governed by the exit rate which depends on the structure of the porphyrin and on its charge determined by pH.