In vitro and in silico insights into the molecular interaction mechanism of acetylshikonin with bovine serum albumin

Acetylshikonin (ASK), as a privileged naphthoquinone derivative with unique spectroscopic properties, is considered an effective substance in biomedical areas. This manuscript was purposefully undertaken for systematic characterization of ASK-bovine serum albumin (BSA) binding to best understand the pharmaceutics properties of ligand, and deep illustration of conformational changes of BSA on the addition of ASK. The overall results of surface plasmon resonance (SPR) and fluorescence spectroscopy indicated temperature dependence of binding constant attributes. Further, thermodynamic analysis on the BSA -ASK interaction (delta G = -23 kJ, delta H = 215 kJ, and delta S = 803 J) unraveled viable, hydrophobic and hydrogen bonds in moderate-affinity complex formation (k(b) of 10(4) M-1). Circular dichroism (CD) spectroscopy suggested the addition of ASK leads to secondary structure changes of BSA, by increasing alpha-helixes content. In addition, atomic force microscopy (AFM) and dynamic light scattering (DLS) techniques showed that ASK causes slight conformational shrinkage, by coalescing BSA to form large particles. Molecular modeling showed the flexibility of the hydrophobic pocket between subdomains IIA and IIB induced an allosteric modulation in BSA structure, thereby localizing itself in the proximity of the tryptophan (Trp-213) residue. Taken together, the results of ASK-BSA interaction can be of great importance for expanding the bio-applications of shikonin. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study systematically characterized the binding of ASK and BSA to understand the pharmaceutics properties of the ligand and the conformational changes of BSA upon the addition of ASK. The results indicated a temperature-dependent binding constant between ASK and BSA. Thermodynamic analysis revealed viable hydrophobic and hydrogen bonds in the moderate-affinity complex formation. CD spectroscopy showed changes in the secondary structure of BSA, with an increased content of alpha-helices upon the addition of ASK. AFM and DLS techniques demonstrated slight conformational shrinkage and the formation of large particles upon ASK binding. Molecular modeling suggested allosteric modulation of BSA structure in the vicinity of the tryptophan residue. Overall, the results of ASK-BSA interaction have significant implications for expanding the bio-applications of shikonin.