Thermodynamic aspects of binding proteins with porphyrins. Spectral and thermochemical approaches

Abstract

The results of spectral and thermochemical studies of the interaction of bovine serum albumin with anionic and cationic porphyrins are presented in this paper. The limits of different methods for the determination of binding constants and thermodynamic parameters were shown. On the basis of spectral studies the binding constants of albumin with the porphyrins were evaluated. The fluorescence quenching constants of the protein at the porphyrins titration were estimated and it was found that in the albumin-porphyrin systems the static and dynamic quenching mechanisms are combined. The thermodynamic parameters were determined using of Van’t Hoff equation from spectral data and the method of isothermal titration calorimetry. It was established that the stability constant of anionic complex is higher than that for complex of cationic porphyrin with albumin.