Thermodynamics and Kinetics of Supramolecular Complex Formation between Carboxymethylcellulose and Lactoferrin

In this study, the kinetics and thermodynamics of the interaction between bovine lactoferrin (BLF) and sodium carboxymethylcellulose (CMC) were investigated using surface plasmon resonance (SPR) and steady-state fluorescence spectroscopy (FS). SPR measurements suggested that the formation of the BLF-CMC complex occurs without significant conformational changes in the biopolymers (k _a ∼ 10⁵ L mol^-1 s^-1 and k _d ∼ 10^-2 s^-1). In both techniques, the binding constant was on the order of ∼10⁶ mol^-1 L and ΔG ^o< 0. Although the SPR data indicated that BLF-CMC complex formation is entropically driven (57 ≤ TΔS _SPR ^o ≤ 60 kJ mol^-1), the FS assays showed exothermic ΔH _FS ^o values (-96 and -31 kJ mol^-1) up to 20 °C and endothermic (39, 111, and 187 kJ mol^-1) at temperatures ≥ 25 °C, while the TΔS _FS ^o values ranged from -58 to 230 kJ mol^-1. This study provides useful insights into the formation of soluble BLF-CMC complexes, which may facilitate their application in the food industry.