Local anesthetic-bovine serum albumin interactional behaviour: Characterization by volumetric, calorimetric, and spectroscopic methods

Interaction Study between ESIPT Fluorescent Lipophile-Based Benzazoles and BSA

In this study, the interactions of ESIPT fluorescent lipophile-based benzazoles with bovine serum albumin (BSA) were studied and their binding affinity was evaluated. In phosphate-buffered saline (PBS) solution these compounds produce absorption maxima in the UV region and a main fluorescence emission with a large Stokes shift in the blue–green regions due to a proton transfer process in the excited state. The interactions of the benzazoles with BSA were studied using UV-Vis absorption and steady-state fluorescence spectroscopy. The observed spectral quenching of BSA indicates that these compounds could bind to BSA through a strong binding affinity afforded by a static quenching mechanism (K_q~10¹² L·mol⁻¹·s⁻¹). The docking simulations indicate that compounds 13 and 16 bind closely to Trp134 in domain I, adopting similar binding poses and interactions. On the other hand, compounds 12, 14, 15, and 17 were bound between domains I and III and did not directly interact with Trp134.

Ligand binding constants for human serum albumin evaluated by ratiometric analysis of DSC thermograms

This paper describes an expanded application of our recently reported method (Eskew et al., Analytical Biochemistry 621,1 2021) utilizing thermogram signals for thermal denaturation measured by differential scanning calorimetry. Characteristic signals were used to quantitatively evaluate ligand binding constants for human serum albumin. In our approach the ensemble of temperature dependent calorimetric responses for various protein-ligand mixtures and native HSA were compared, in a ratiometric manner, to extract binding constants and stoichiometries. Protein/ligand mixtures were prepared at various ligand concentrations and subjected to thermal denaturation analysis by calorimetry. Measurements provided the melting temperature, T_m, and free-energy ΔG_cal(37°C) for melting ligand-bound Albumin as a function of ligand concentration. Concentration dependent behaviors of these parameters derived from protein/ligand mixtures were used to construct dose-response curves. Fitting of dose-response curves yielded quantitative evaluation of the ligand binding constant and semi-quantitative estimates of the binding stoichiometry. Many of the ligands had known binding affinity for Albumin with binding constants reported in the literature. Evaluated binding parameters for the ligands impressively agreed with reported literature values determined using other standard experimental methods. Results are reported for 29 drug ligands binding to Albumin. These validate our calorimetry-based process for applications in pre-clinical drug screening.

Interaction study of monoisoamyl dimercaptosuccinic acid with bovine serum albumin using biophysical and molecular docking approaches

Monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA), a lipophilic chelator has been evaluated for its potential use as an antidote in arsenic poisoning. The pharmacokinetics and pharmacodynamics properties of a drug could be understood via study its mechanism of interaction with bovine serum albumin protein (BSA). Therefore, the interaction between MiADMSA with BSA was investigated using various spectroscopic techniques and computational methods. Linear quenching of BSA intrinsic fluorescence intensity with the increasing concentration of MiADMSA was observed in the fluorescence study. Furthermore, synchronous results revealed that MiADMSA slightly changed the conformation of BSA. The binding constant value of the BSA-MiADMSA complex was found 1.60 × 104 M-1 at 298 K. The value of thermodynamic parameters ΔG, ΔH, and ΔS described that the process is spontaneous, endothermic, and hydrophobic forces are involved in the interaction of MiADMSA with BSA. Competitive site marker experiments showed that MiADMSA binds to site-II of BSA. Conformational changes of BSA with the interaction of MiADMSA were apparent by CD, UV-Visible, FT-IR, and 3D fluorescence spectroscopy. To strengthen the experimental findings we have also performed a theoretical study on the BSA-MiADMSA complex. Two sites were identified with docking score of - 6.642 kcal/mol at site IIa and - 3.80 kcal/mol for site IIb via molecular docking study. Molecular dynamics simulation study inferred the stability of the BSA-MiADMSA complex which was analyzed in a long simulation run. The experimental and computational studies have shown the effective binding of MiADMSA with BSA which is essential for the transportation and elimination of a drug from the body.