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 10(5)L.mol(-1) by fluorescence and microcalorimetric, and 10(3) and 10(4) L.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 (Delta H-F(Omicron) = -8.67 kJ.mol(-1)), while microcalorimetry showed an entropic driven binding process (Delta H-cal(Omicron) = 29.11 kJ.mol(-1)). For the unfolded BSA/curcumin complex, it was found thatp Delta H-F(Omicron) = -16.12 kJ.mol(-1) and Delta H-cal(Omicron) = -42.63 kJ.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.