Application of Congo red dye as a molecular probe to investigate the kinetics and thermodynamics of the formation processes of arachin and conarachin nanocomplexes.

• Peanut proteins (ARA or CON) interact with Congo red (CR) to form stable complexes. • CON has a higher binding affinity toward CR than does ARA. • Hydrophilic interactions were the main driving forces for [ A R A - C R ] 0 formation process. • The formation of [ C O N - C R ] 0 was enthalpically and entropically driven. • Transition complexes had a more structured conformation than their stable form. The thermodynamics and kinetics of arachin-Congo red (ARA - C R) and conarachin-Congo red (CON - C R) interactions were studied using surface plasmon resonance. KCl led to a reduction of up to 55% in the values of the associated kinetic constants, but it had less influence on the dissociation rates (less than 12%). The change in ionic strength had little effect on the thermodynamic stability of the complexes, but it did reduce their affinities (K b ( 25 ° C) [ A R A - C R ] 0 from 3.52 to 2.44 × 103 M−1 and K b (25 ° C) [ C O N - C R ] 0 from 15.1 to 12.5 × 103 M−1). The shielding of the electrical double layer favored ARA - C R hydrophilic interactions (Δ H [ A R A - C R ] 0 0 decreased from −30.60 to −42.98 kJ mol−1). On the other hand, hydrophobic interactions came to dominate during the formation of [ C O N - C R ] 0 (Δ H [ C O N - C R ] 0 0 increased from −11.21 to 28.34 kJ mol−1 and T Δ S 25 ° C [ C O N - C R ] 0 0 increased from 12.64 to 51.73 kJ.mol−1). The data presented here improve our understanding of plant-based protein nanocarriers of small bioactive molecules. [ABSTRACT FROM AUTHOR]