Temperature modulation of lutein-lysozyme hydrophobic-hydrophilic interaction balance

The formation of nanocomplexes between lutein (Lut) and lysozyme (Lys) is an alternative method of transporting Lut and improving its chemical stability. To optimize the formation of the Lut-Lys complex, binding assays were performed in the temperature range of 12-28 degrees C using real-time label-free surface plasmon resonance (SPR). Kinetics analysis showed that about 2000 Lut-Lys complexes are formed per second, of which 36% dissociate per second. The speed of formation of the activated complex was not affected by temperature because the Gibbs free energy barriers were almost constant (Delta(double dagger)G(a)(0)congruent to 53 and Delta(double dagger)G(d)(0)congruent to 74 klmol(-1)). There was a critical temperature (T congruent to 1836 degrees C), below it the hydrophobic forces dominated (Delta H-double dagger(a)0 and Delta H-double dagger(d)0 > 0) and above it hydrophilic interactions (Delta H-double dagger(a)0 and Delta H-double dagger(d)0 < 0), such as van der Waals and hydrogen bonds, determined the activated complex formation. The stability of the thermodynamic complex was temperature-independent (Delta G(0) congruent to - 21 kJ mol(-1)); however, the relative hydrophobic/hydrophilic contributions to the enthalpy and entropy change for the formation of this complex were dependent on the temperature (Delta H-0 = 11.72 to - 36.71 kJ.mol(-1) and T Delta S-0 = 32.11 to - 15.54 kJ.mol(-1)). The SPR data provide useful insight for the discovery of potential luteinprotein nanocan-iers. (C) 2020 Published by Elsevier B.V.