Analysis of the binding mechanism for a water-soluble Pd(II) complex containing β-amino alcohols with HSA applying experimental and computational methods

Abstract

In the study ahead, the binding interactions of the [Pd (HEAC) Cl₂] complex with human serum albumin (HSA) protein have been assayed in vitro (pH= 7.40) utilizing computational and experimental procedures. The mentioned complex was synthesized as a water-soluble complex from {2-((2-((2-hydroxyethyl)amino)ethyl)amino) cyclohexanol} ligand = HEAC. The results of electronic absorption and circular dichroism investigations illustrated that the hydrophobicity of the Tryptophan microenvironment in HSA undergoes the changes by binding to the Pd(II) complex without substantial perturbations on the protein secondary structure. The fluorescence emission spectroscopy analysis revealed that with rising temperature, the quenching constant (K_sv) in the Stern–Volmer’s relation decreases; so, it can be said that the interaction process is along with a static quenching mechanism. The values of 2.88 × 10⁵ M⁻¹, and 1.26 represent the binding constant (K_b) and the number of the binding sites (n), respectively. The Job graph showed the maximum point at χ = 0.5, which means organizing a new set with 1:1 stoichiometry. Thermodynamic profile (ΔH < 0, ΔS < 0, and ΔG < 0) has affirmed that van der Waals forces and hydrogen bonds have a basic function in the Pd(II) complex-albumin bindings. The ligand-competitive displacement studies utilizing warfarin and ibuprofen have represented that Pd(II) complex interacts with albumin by site II (subdomain IIIA). The computational molecular docking theory approved the results of the site-competitive tests; also, it indicated the existence of hydrogen bonds and van der Waals forces in Pd(II) complex-albumin interactions.

Communicated by Ramaswamy H. Sarma

Keywords:

• Multi-spectrophotometric and computational methods
• human serum albumin
• Pd(II) complex
• fluorescence quenching
• site II/subdomain IIIA

Acknowledgments

The financing support of the Razi University Research Center is greatly appreciated.

Authors’ contributions

The authors entirely participated in the conception, design, and manuscript of the research. The first draft of this manuscript was written by Nahid Shahabadi. Lida Ghaffari participated in the experiments section, Zahra Mardani participated in the Pd(II)complex identification, and Saba Hadidi participated in the computational and theoretical studies. The authors read and verified the final manuscript.

Disclosure statement

The authors have no conflict of interest

Ethical confirmation

The research does not include the participation of human or animal species by any of the authors.

Availability of Information, Data, and Materials

All details and data are accessible in the paper.

Additional information

Funding

This investigation was conducted with the financial support of Razi University Research Center and the National Science Foundation of Iran (INSF).