Thermodynamic and kinetic analyses of curcumin and bovine serum albumin binding.

Bovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 105L·mol-1 by fluorescence and microcalorimetric, and 103 and 104L·mol-1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH○F=-8.67kJ·mol-1), while microcalorimetry showed an entropic driven binding process (ΔH○cal=29.11kJ·mol-1). For the unfolded BSA/curcumin complex, it was found thatp ΔH○F=-16.12kJ·mol-1 and ΔH○cal=-42.63kJ·mol-1. BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding.