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Updated: Oct 27, 2026

Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores
Published on: April 5, 2022
Spectroscopic and computational studies on biophysical aspects of ivermectin binding with human hemoglobin:
M Prabhavathi1,2, K Lavanya3, B Samuel Raju4
1Department of Chemistry, GITAM School of Science, GITAM Deemed to be University Hyderabad Campus, Hyderabad, 502329, India.
Abstract:
Proteins are known to play multifunctional role including transportation, storage, structural support among others. Among the proteins, hemoglobin (Hb) is known to transport oxygen and binds with many xenobiotics and therapeutic drugs. But, in this paper, the binding of human hemoglobin (HHb) with Ivermectin (IVM) that is a broad-spectrum antiparasitic agent used during COVID-19 pandemic has been presented. Multi-spectroscopic experimental techniques and in-silico docking methods have been used for the intended study. IVM quenched HHb fluorescence via a dynamic quenching process with a quenching constant (Ksv) on the order of 105 M- 1. TCSPC studies confirmed the dynamic quenching by showing a decrease in the lifetime of the fluorophore (HHb) in presence of IVM. The binding affinity (Kb) from UV-Vis and fluorescence studies was on the order of 105 M- 1. The binding constant was observed to increase with rise in temperature. Thermodynamic parameters of the interaction (ΔG⁰, ΔH⁰, ΔS⁰) indicated a spontaneous binding process with negative free energy changes and an entropy driven process due to T∆S0 > ∆H0. A positive value of both enthalpy (ΔH⁰) and entropy (ΔS⁰) changes accompanying the binding showed the driving role of hydrophobic forces in the interaction. Synchronous fluorescence results revealed no considerable changes in the microenvironment of tryptophan (Trp) and tyrosine (Tyr). A visible conformational variation in the secondary structure of HHb especially the α-helix was evident from 3D-fluorescence and circular dichroism (CD) studies. Theoretical docking studies showed the binding site of IVM in the central cavity of HHb. The limitation of this study includes the lack of molecular dynamics simulations to model real-time stability of the complex.
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