Uncovering the Interaction of 2‐(4‐Aminophenyl) benzothiazole with Human Serum Albumin: A Combined Spectroscopic and Docking Study

Abstract Drug interactions with receptors determine their biological activity. Among the proteins, human serum albumin (HSA) is most commonly used as the model protein to explore such interactions. The heterocyclic molecule, 2‐(4‐aminophenyl) benzothiazole (APB), is known to have various biological potential. The binding of APB with HSA has been presented by looking into the binding parameters and the binding effect on the structural aspect of the protein. The binding constant (K b ), number of binding sites (n), quenching constant (K SV ), and bimolecular quenching constant (k q ) have been estimated from experimental spectroscopic methods. The binding and quenching constant was found to be in the order of 10 5 M −1 . Quenching of HSA fluorescence at 303, 308, and 313 K by APB showed a dynamic nature of quenching. The binding was spontaneous with a negative free energy change (ΔG 0 ). The binding's enthalpy (ΔH0) and entropy (ΔS0) changes suggested the significant role of electrostatic force. Site‐specific marker displacement studies revealed the binding of APB in subdomain IIA. Circular dichroism (CD) studies revealed no visible structural changes in HSA. The experimental finding was corroborated by molecular docking studies that showed the location of APB in subdomain IIA. This study may help understand the interactions of its analogues or related structures with the protein and aid in designing molecules with better potential.