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.

A multifaceted approach to investigate interactions of thifluzamide with haemoglobin

This study explores the interaction between the pesticide thifluzamide (TF) and haemoglobin (Hb) to understand potential structural changes that might affect Hb's function. Using a combination of UV-Visible and fluorescence spectroscopy, circular dichroism (CD), molecular docking, molecular dynamics (MD) simulations, and electrochemical methods, we investigated these interactions in detail. Spectroscopy results indicated the formation of a stable TF-Hb complex, with a binding constant of 6.64 × 105 M-1 at 298 K and a 1:1 binding ratio. The stability of this complex was confirmed by a free energy change (∆G) of -34.491 kJ mol-1. CD spectroscopy was employed to confirm structural changes in Hb due to thifluzamide binding. Molecular docking studies revealed that TF interacts with specific amino acids in Hb like ALA, HIS, VAL, LYS, and LEU, with a binding energy of -25.10 kJ mol-1. MD simulations supported these findings by showing conformational changes in Hb upon TF binding, as indicated by RMSD and RMSF analyses. Electrochemical experiments further confirmed the interaction, evidenced by a consistent decrease in the TF's peak in the presence of Hb. Overall, our findings shed light to understand the binding of TF with Hb, causing structural changes that could potentially impact its normal function. This research enhances our understanding of the biochemical effects of TF on Hb, which could have significant implications for biological systems.

Exploring the Structural Importance of the C3=C4 Double Bond in Plant Alkaloids Harmine and Harmaline on Their Binding Interactions with Hemoglobin

Harmine and harmaline are two structurally similar heterocyclic β-carboline plant alkaloids with various therapeutic properties, having a slight structural difference in the C3=C4 double bond. In the present study, we have reported the nature of the interaction between hemoglobin (Hb) with harmine and harmaline by employing several multispectroscopic, calorimetric, and molecular docking approaches. Fluorescence spectroscopic studies have shown stronger interaction of harmine with Hb compared to that of almost structurally similar harmaline. Steady-state anisotropy experiments further show that the motional restriction of harmine in the presence of Hb is substantially higher than that of the harmaline-Hb complex. Circular dichroism (CD) study demonstrates no conformational change of Hb in the presence of both alkaloids, but CD study in 1-cm cuvette path length also demonstrates stronger affinity of harmine toward Hb compared to harmaline. From the thermal melting study, it has been found that both harmine and harmaline slightly affect the stability of Hb. From isothermal titration calorimetry (ITC), we have found that the binding process is exothermic and enthalpy driven. Molecular docking studies indicated that both harmine and harmaline prefer identical binding sites in Hb. This study helps us to understand that slight structural differences in harmine and harmaline can alter the interaction properties significantly, and this key information may help in the drug discovery processes.

Comparative assessment of 9-bromo noscapine ionic liquid and noscapine: Synthesis, in-vitro studies plus computational & biophysical evaluation with human hemoglobin

Noscapine is a proficient anticancer drug active against wide variety of tumors including lung cancer. Over time, several noscapine analogues have been assessed to maximize the efficiency of the drug, amongst which 9-bromo noscapine remains one of the most potent analogues till date. In the present work, we have synthesized 9-bromo noscapine ionic liquid [9-Br-Nos]IBr2, an active pharmaceutical ingredient based ionic liquid (API-IL) to address the existing issues of solubility and targeted drug delivery in the parent alkaloid as well as the synthesized analogues. We have devised a novel two-step synthesis route (first-ever ionic to ionic bromination) to obtain the desired [9-Br-Nos]IBr2 which is advantageous to its organic analogue in terms of increased solubility, lesser reaction time and better yield. Furthermore, we have compared 9-bromo noscapine ionic liquid with noscapine based on its binding interaction with human hemoglobin (Hb) studied via computational along with spectroscopic studies, and bioactivity against non-small cell lung cancer. We inferred formation of a complex between [9-Br-Nos]IBr2 and Hb in the stoichiometric ratio of 1:1, similar to noscapine. At 298 K, [9-Br-Nos]IBr2-Hb binding was found to exhibit Kb and ∆G of 36,307 M-1 and -11.5 KJmol-1, respectively, as compared to 159 M-1 and -12.5 KJmol-1 during Noscapine-Hb binding. This indicates a more stronger and viable interaction between [9-Br-Nos]IBr2 and Hb than the parent compound. From computational studies, the observed higher stability of [9-Br-Nos]I and better binding affinity with Hb with a binding energy of -91.75 kcalmol-1 supported the experimental observations. In the same light, novel [9-Br-Nos]IBr2 was found to exhibit an IC50 = 95.02 ± 6.32 μM compared to IC50 = 128.82 ± 2.87 μM for noscapine on A549 (non-small lung cancer) cell line at 48 h. Also, the desired ionic liquid proved to be more cytotoxic inducing a mortality rate of 87 % relative to 66 % evoked by noscapine at concentrations of 200 μM after 72 h.

A new chiral stationary phase based on noscapine: Synthesis, enantioseparation, and docking study

Noscapine is an isolated compound from the opium poppy, with distinctive chiral structure and chemistry, interacts with other compounds due to having multiple π-acceptors, hydrogen bond acceptors, and ionic sites. Therefore, it has promising applicability for the enantioselective separation of a wide range of polar, acidic, basic, and neutral compounds. A new noscapine derivative chiral stationary phase (ND-CSP) has been synthesized by consecutive N-demethylation, reduction, and N-propargylation of noscapine followed by attachment of a solid epoxy-functionalized silica bed through the 1,3-dipolar Huisgen cycloaddition. The noscapine derivative-based stationary phase provides a considerable surface coverage, which is greater than some commercial CSPs and can validate better enantioresolution performance. The major advantages inherent to this chiral selector are stability, reproducibility after more than 200 tests, and substantial loading capacity. The characterization by Fourier transform infrared (FTIR) spectroscopy and elemental analysis indicated successful functionalization of the silica surface. Chromatographic method conditions like flow rate and mobile phase composition for enantioseparation of various compounds such as warfarin, propranolol, mandelic acid, and a sulfanilamide derivative were optimized. Comparing the experimental results with docking data revealed a clear correlation between the calculated binding energy of ND-CSP and each enantiomer with the resolution of enantiomer peaks.