Hemoglobin targeting potential of aminocarb pesticide: Investigation into dynamics, conformational stability, and energetics in solvent environment

Aminocarb (AMC), a carbamate pesticide, due to its prevalent usage exhibits increased accumulation in the environment affecting both insects and humans. It enters the human body via food grains and be transported through bloodstream. AMC's chemical structure, containing specific molecular frameworks and functional groups, enables it to bind with proteins like albumin and hemoglobin. Given that molecules with similar architecture are known to bind with hemoglobin, we aimed to explore Aminocarb's binding capability and the potential mechanism or mode of its interaction with hemoglobin. Hb being a tetramer with a profound interface between amino acid chains offers multiple binding sites. It is therefore important to investigate the structural aspects of binding of AMC by employing various spectroscopic and in-silico methods. The surface of the α1 chain near the α1β2 interface emerges as the preferred binding site for AMC, primarily due to its conformational restrictions. In its bound state, AMC tends to maintain a relaxed conformation, closely resembling its globally optimized geometry, and resides in close proximity to the α1 chain via multiple hydrophobic contacts and water bridge as observed in molecular dynamics (MD) simulations. Fluorescence quenching experiments showed moderate binding strength (7.7 × 10⁴ L M⁻¹ at 288 K, 7.8 × 10⁴ L M⁻¹ at 298 K, 7.9 × 10⁴ L M⁻¹ at 308 K) and spontaneous binding, driven by hydrophobic and van der Waals interactions, as indicated by enthalpy (0.80-0.91 kJ mol⁻¹), entropy (0.0970-0.0974 kJ mol⁻¹), and Gibbs free energy (-27.13 to - 29.08 kJ mol⁻¹). Circular dichroism experiments reveal no major structural changes in Hb. Quantum chemical calculations and MD simulations reveal conformation-dependent energy differences, enhancing our understanding of AMC's binding mechanism to Hb.