Influence of protein conformation and selected Hofmeister salts on bovine serum albumin/lutein complex formation.

Protein conformation and the 3D water structure play important roles in the ability of bovine serum albumin (BSA) to form stable nanostructures with bioactive molecules. We studied the influence of BSA unfolding and those of two Hofmeister salts, sodium chloride (NaCl) as kosmotrope and sodium thiocyanate (NaSCN) as chaotrope, on BSA/lutein binding at pH 7.4 using fluorescence spectroscopy. The BSA/lutein complex formation was entropically driven and lutein was preferentially bound to site III of BSA. The binding constant (104 L mol-1), complex stoichiometry (1:1), and thermodynamic potential for BSA/lutein binding were independent of protein conformation and Hofmeister salts. However, the enthalpic and entropic components of BSA/lutein binding in the presence of NaSCN decreased as the temperature increased. The opposite was observed for BSA/lutein binding in the presence of NaCl and for denatured BSA/lutein binding. Therefore, the BSA conformation and 3D water structure directly affected the BSA/lutein binding thermodynamics.

Naringenin-lactoferrin binding: Impact on naringenin bitterness and thermodynamic characterization of the complex.

Naringenin (NG) is a flavonoid with many bioactive properties, however, its bitterness limits its use in foods. It is known that complex formation with proteins can mask this undesirable sensory property. Therefore, a trained panel evaluated the effect of bovine lactoferrin (LF) on NG bitterness using time-intensity analysis. LF reduced the maximum bitterness intensity and overall bitterness perception for NG by 27% and 33%, respectively. Isothermal titration nanocalorimetry (ITC), molecular docking (DC), and molecular dynamics (MD) were used to characterize NG-LF binding. These techniques provided similar values of ΔG° for binding ( [Formula: see text]  = -33.42 kJ mol-1; [Formula: see text]  = -32.22 kJ mol-1; [Formula: see text]  = -31.84 kJ mol-1). ITC showed that the complex formation is primarily entropy driven and DC suggested that NG binds at a hydrophobic site in LF. Here are presented strategic tools for promoting NG incorporation in food and health products.

Surface plasmon resonance study of interaction between lactoferrin and naringin.

Lactoferrin (LF) is a glycoprotein that serves as a potential vehicle for small bioactive molecules in food. In an effort to improve this functionality, the kinetic and thermodynamic interaction of LF with naringin (NR) was studied by surface plasmon resonance (SPR). The results demonstrated that the association rate constant between LF and NR was 5.00 × 104 M-1 s-1, while the dissociation rate of the complex was 0.36 s-1, at 25 °C. The stable complex predominated over free molecules (ΔG25°C0=-29.35 kJ mol-1), and the binding constant was 1.39 × 105 M-1, at 25 °C. The association of LF and NR to form an intermediate complex occurred in multi-steps. Nevertheless, the intermediate complex formation from the dissociation of the stable complex occurred in a single step with the activation energy independent of temperature. This study provides an important basis to explore LF as a vehicle for bioactive molecules.