Insights into protein-curcumin interactions: Kinetics and thermodynamics of curcumin and lactoferrin binding.

The thermodynamics of curcumin (CUR) binding with bovine lactoferrin (bLF) was investigated by employing fluorescence spectroscopy (FS) and surface plasmon resonance (SPR) and comparing the results. Moreover, the kinetics of bLF-CUR binding was studied using SPR. FS data showed that with an increase in temperature (from 293.15 to 306.15 K), more complexes were formed (K b ranged from 2.07 × 104 to 6.68 × 104 M−1) owing to an increase in the entropy (Δ H ° = 66.70 kJ mol−1; T Δ S ° ranged from 90.93 to 94.98 kJ mol−1), demonstrating the role of hydrophobic interactions. However, the bLF-CUR complex formation detected through the SPR technique was entropically and enthalpically driven below and above 293.75 K, respectively. SPR also demonstrated that an enthalpy increase is compensated by an entropy increase for both stable and activated complex formation, characterizing enthalpy-entropy compensation and iso-kinetic compensation, respectively. These results are helpful to better understand the dynamics of complex formation between proteins and small bioactive molecules. Image 1 • Curcumin (CUR) and bovine lactoferrin (bLF) formed a stable complex. • SPR showed that bLF has more sites for CUR binding than those close to tryptophan. • The stable bLF-CUR complex formation passes through an intermediate state. • The bLF-CUR interaction occurred with enthalpy-entropy compensation. • bLF-CUR binding is driven mainly by the conformational and desolvation processes. [ABSTRACT FROM AUTHOR]