Thermodynamic Analysis of the Interaction between Cationic Porphyrins and Human Serum Albumin by an Optical Biosensor

An optical biosensor with a stirred cuvette has been used to monitor the interaction between immobilized human serum albumin (HSA) and three water-soluble cationic porphyrins. The binding constants at 25°C obtained from biosensor analysis were compared with those from fluorescence spectroscopy. The interactions were further investigated at temperatures from 15°C to 30°C. The thermodynamics parameters, changes of free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), were evaluated from equilibrium data. It appeared that the binding process was governed primarily by electrostatic forces. © 2005 SIOC, CAS, & Wiley-VCH Verlag GmbH & Co. KGaA.