New perspective of the ternary complex of nano-curcumin with β-lactoglobulin in the presence of α-lactalbumin: Spectroscopic and molecular dynamic investigations

Understanding the interaction between nano-curcumin (Nano Cur) and proteins is essential for elucidating the potential therapeutic applications of curcumin in nano formulations. In this study, we investigated the interactions of Nano Cur and two important milk proteins, β-lactoglobulin and α lactalbumin as binary and ternary systems, in molecular-level through the employment of various biophysical methods including various different spectroscopies, and molecular dynamic simulations. Fluorescence spectroscopy analysis revealed distinct changes in the fluorescence emission of both proteins upon binding to Nano Cur as an indication of protein-Nano Cur complexes formation. The non-linear Stern-Volmer plots of β-lactoglobulin-Nano Cur complex formation in the absence and presence of α-lactalbumin displayed two set of binding sites that referred to the dominance of two different interaction behaviors with two set of binding sites. Also, the comparison between Ksv and Kb values of β-lactoglobulin-Nano Cur in the absence and presence of α-lactalbumin with the temperatures revealed the influence of combined dynamic and static quenching. Circular dichroism measurements further provided insights into the potential enhancement of the secondary structure of proteins upon interaction with Nano Cur through the induced alterations. In order to access a deeper view on the dynamic behavior of protein-Nano Cur complexes, time-resolved fluorescence measurements were performed to reveal the kinetics of interaction process. Additionally, molecular dynamic simulations were employed to simulate the atomic-level interactions and explore the stability and conformational changes of protein-Nano Cur complexes over time. The results of these comprehensive biophysical investigations shed light on the binding characteristics, structural alterations, and dynamic behavior of Nano Cur upon interaction with β-lactoglobulin in the absence and presence of α-lactalbumin as the binary and ternary systems. This study reveals the Nano-Cur role in the protein–protein interaction behavior and provides valuable insights into the potential applications of α-lactalbumin in the design of functional food formulations and drug delivery systems.