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 105 L?mol?1 by fluorescence and microcalorimetric, and 103 and 104 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 (?H?F = ?8.67 kJ?mol?1), while microcalorimetry showed an entropic driven binding process (?H?cal = 29.11 kJ?mol?1). For the unfolded BSA/curcumin complex, it was found thatp ?H?F = ?16.12 kJ?mol?1 and ?H?cal = ?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