Exploring the interaction between tyrphostin 9 and human serum albumin using biophysical and computational methods

Unveiling the binding details and esterase-like activity effect of methyl yellow on human serum albumin: spectroscopic and simulation study

The food sector uses methyl yellow (MY) extensively as a colorant. The primary transporter in vivo that influences MY absorption, metabolism, distribution, and excretion is human serum albumin (HSA). Exploring the binding process and looking at how HSA and MY work physiologically at the molecular level is therefore very important. Experiments using steady-state fluorescence and fluorescence lifetimes proved that HSA and MY's quenching mechanisms were static. The HSA-MY complex's binding constant was estimated using thermodynamic parameters to be around 10⁴ M^-1. The hydrophobic forces were a major factor in the binding process, as evidenced by the negative ΔG, positive ΔH, and ΔS, which suggested that this contact was spontaneous. Site tests showed that MY linked to HSA's site I. Circular dichroism and three-dimensional fluorescence analysis revealed that the 1.33% α-helix content dropped and the amino acid microenvironment altered. While HSA's protein surface hydrophobicity decreased when engaging MY, the binding of MY to HSA reduced in the presence of urea. The stability of the system was assessed using molecular modeling. Additionally, HSA's esterase-like activity decreased when MY was present, and Ibf/Phz affected the inhibition mechanism of MY on HSA. These findings offer a distinctive perspective for comprehending the structure and functioning of HSA and evaluating the safety of MY.

Biomolecular interaction mechanism of an anticancer drug, pazopanib with human serum albumin: a multi-spectroscopic and computational approach

Pazopanib (PZP) is a multi-targeting tyrosine kinase inhibitor and is currently approved by FDA for the treatment of soft tissue sarcoma and renal cancer. Molecular interaction mechanism of PZP with human serum albumin (HSA) was explored under simulated physiological conditions (pH = 7.4), using fluorescence and UV absorption spectroscopy along with computational methods. Based on the inverse correlation between the Stern-Volmer constant (K_sv) and temperature, it was concluded that PZP quenched the protein fluorescence through static quenching mechanism. This was also confirmed from the UV-vis absorption spectral results. Moderate binding affinity between PZP and HSA was evident from the K_a values (5.51 - 1.05 × 10⁵ M^-1) while PZP-HSA complex formation was driven by hydrophobic and van der Waals interactions as well as hydrogen bonds, as revealed by positive entropy change (ΔS = +98.37 J mol^-1 K^-1) and negative enthalpy change (ΔH = -60.31 kJ mol^-1). Three-dimensional fluorescence spectral results disclosed microenvironmental perturbations around Trp and Tyr residues of the protein upon PZP binding. Interestingly, the addition of PZP to HSA significantly protected the protein against thermal stress. Competitive drug displacement results obtained with warfarin, phenylbutazone and diazepam elucidated Sudlow's Site I, positioned in subdomain IIA of HSA, as the preferred binding site of PZP which was well supported by molecular docking analysis, while molecular dynamics simulation results suggested the stability of the PZP-HSA complex.Communicated by Vsevolod Makeev.