Structural Characteristics and Binding Mechanism of Native and Thermally Modified Lactoferrin-curcumin Complexes

The structural characteristics and binding mechanism of native and thermally modified lactoferrin(LF)and curcumin(Cur)were investigated by turbidimetry,dynamic light scattering,infrared spectra,circular dichroism and fluorescence spectrain to solve the problem of poor aqueous solubility of Cur. The results showed that turbidity and particle size of LF-Cur complexes were closely related to the structure of LF and concentration of Cur. Native LF-Cur complexes were nanoparticles at the Cur concentration of 1.4×10^-5~5.4×10^-5 mol/L with the low-level turbidity and submicremeter particles at the Cur concentration of 8.1×10^-5~1.08×10^-4 mol/L with the high-level turbidity. Thermally modified LF-Cur complexes were all nanoparticles. The ζ-potential of LF-Cur complexes was increased by the increasing of Cur concentration. Far-UV circular dichroism results indicated that heat denaturation might irreversibly alter the secondary structure of LF. The addition of Cur might alter the secondary structure of native and thermally modified LF. Analysis of infrared spectra results showed that Cur could bind to LF through the hydrogen bond. Fluorescence spectra results indicated that the combination of Cur with native and thermally modified LF was a static quenching process and thermally modified LF exhibited a strong affinity for Cur. Thermal denaturation could improve the encapsulation efficiency of LF to Cur. These results could provide a theoretical basis for the development of LF as a carrier of hydrophobic polyphenols.