Spectroscopic and molecular docking investigation of the binding of a bioactive mercaptobenzimidazole-functionalized Schiff base to human serum albumin

Multispectroscopic Studies on HSA Interaction, DFT Calculations, Molecular Docking, and Antimicrobial Activities of Imine‐ Functionalized Tris(hydroxymethyl)aminomethane Derivatives

Following recent work on new Tris hydroxymethyl aminomethane Schiff base derivatives were synthesized and characterized by using NMR (1H, 13C, and depth), FT‐IR, and Mass spectroscopy. The crystal structure of STB has been determined by X‐ray diffraction analysis. The binding interaction of the 3 chemically synthesized molecules with human serum albumin has been examined under the pH=7.40 through UV‐visible absorption and fluorescence spectroscopy analysis. The result obtained from the fluorescence experiment (1014) suggests a static mechanism of quenching. By utilizing fluorescence spectroscopy to determine the binding constant (Kb=106), it was determined which ligands have the highest affinity for HSA and that these ligands had changed the structure of HSA. Through hydrophobic interactions, the ligands bind to HSA on site I (subdomain II), according to thermodynamic parameters like enthalpy change (ΔHo), entropy change (ΔSo), and Gibbs free energy change (ΔGo). The result of 3D fluorescence spectra also showed that albumin conformational changes were brought on by these ligands. The results of the experiments were supported by DFT and molecular docking of ligands with HSA. Escherichia coli, Stap. aureus, Aspergillus niger, and Aspergillus flavus were tested for antimicrobial activity against the synthesized compounds respectively.

Alterations in the conformation and function of human serum albumin induced by the binding of methyl hydrogen phthalate

Phthalate esters (PAEs) are widely used as plasticizer components in production. Methyl hydrogen phthalate (MHP) is a metabolite of dimethyl phthalate (DMP, a kind of PAEs), and its toxic residues accumulate in the nature and can enter the human body. Here, the interaction between MHP and human serum albumin (HSA) was probed by using multi-spectral, computer simulations, and biochemical techniques. The results showed that MHP was spontaneously embedded in site I of HSA to form a complex by H-bonds and van der Waals forces (ΔH < 0, ΔS < 0). The binding constant (K_a) of the HSA-MHP system was 1.136 ± 0.026 × 10⁴ M^-1 (298 K). The combination of MHP produced conformational variations of HSA, as shown by the 3D fluorescence spectrum, CD spectra, and molecular dynamics simulation. Additionally, molecular docking indicated that MHP was surrounded by multiple residues, such as Lys199, Leu203, Phe206, and Trp214. Specifically, Lys199 and Trp214 exerted a crucial effect on the interaction of HSA and MHP. The residues with important energy contribution were mostly located in site I. The ASA values of the aromatic amino acids of HSA changed after combining with MHP. The R_g and SASA values of HSA increased after adding MHP, suggesting that the structure of HSA was less compact. Moreover, the esterase-like activity of HSA increased after adding MHP to HSA, indicating that MHP may disturb the normal physiological activities in the human body. This study was helpful to understand the biological function of MHP and provided some insights for its side effect in the human body.