Experimental and DFT study on pyrrole tosylhydrazones

New insights into the interactions between the antibiotic enrofloxacin and fish protein by spectroscopic, thermodynamic, and theoretical simulation approaches

In this study, myofibrillar proteins (MPs) from crucian carp were utilized as a model to investigate the binding mechanism between fish proteins and antibiotic residues. Fluorescence quenching confirmed the static quenching (Ksv = 1.89 × 104 M-1 s-1, Kq = 1.89 × 1012 M-1 s-1) and effective binding (Kb = 5.66 × 106 M-1) of Enrofloxacin (ENRO) to MPs. Fourier-transform infrared spectroscopy and circular dichroism spectroscopy revealed that ENRO binding altered the secondary structure of MPs. The interaction mechanism, primarily driven by hydrogen bonding, electrostatic, and hydrophobic interactions (ΔH0 < 0, ΔS0 > 0), was elucidated using isothermal titration calorimetry. The ΔH0, -TΔS0 and ΔG0 values of the binding reaction between MPs and ENRO were -5.98 kJ/mol, -32.57 kJ/mol and -38.55kJ/mol. Molecular docking further verified the interaction forces, identifying key amino acid residues (Phe-40, His-93, and Lys-42) involved in ENRO binding. Additionally, protein carbonylation results demonstrated that even at maximum residue limits, ENRO accelerated MPs oxidation, further confirming the binding of the two. This study can provide theoretical support for the research of the dissipation fate of bound state residues in aquatic products.

Synthesis of Novel Tritopic Hydrazone Ligands: Spectroscopy, Biological Activity, DFT, and Molecular Docking Studies

Polytopic organic ligands with hydrazone moiety are at the forefront of new drug research among many others due to their unique and versatile functionality and ease of strategic ligand design. Quantum chemical calculations of these polyfunctional ligands can be carried out in silico to determine the thermodynamic parameters. In this study two new tritopic dihydrazide ligands, N’2, N’6-bis[(1E)-1-(thiophen-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L1) and N’2, N’6-bis[(1E)-1-(1H-pyrrol-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L2) were successfully prepared by the condensation reaction of pyridine-2,6-dicarboxylic hydrazide with 2-acetylthiophene and 2-acetylpyrrole. The FT-IR, 1H, and 13C NMR, as well as mass spectra of both L1 and L2, were recorded and analyzed. Quantum chemical calculations were performed at the DFT/B3LYP/cc-pvdz/6-311G+(d,p) level of theory to study the molecular geometry, vibrational frequencies, and thermodynamic properties including changes of ∆H, ∆S, and ∆G for both the ligands. The optimized vibrational frequency and (1H and 13C) NMR obtained by B3LYP/cc-pvdz/6-311G+(d,p) showed good agreement with experimental FT-IR and NMR data. Frontier molecular orbital (FMO) calculations were also conducted to find the HOMO, LUMO, and HOMO−LUMO gaps of the two synthesized compounds. To investigate the biological activities of the ligands, L1 and L2 were tested using in vitro bioassays against some Gram-negative and Gram-positive bacteria and fungus strains. In addition, molecular docking was used to study the molecular behavior of L1 and L2 against tyrosinase from Bacillus megaterium. The outcomes revealed that both L1 and L2 can suppress microbial growth of bacteria and fungi with variable potency. The antibacterial activity results demonstrated the compound L2 to be potentially effective against Bacillus megaterium with inhibition zones of 12 mm while the molecular docking study showed the binding energies for L1 and L2 to be −7.7 and −8.8 kcal mol−1, respectively, with tyrosinase from Bacillus megaterium.

Synthesis, spectral analysis, molecular docking and DFT studies of 3-(2, 6-dichlorophenyl)-acrylamide and its dimer through QTAIM approach

In this paper, an experimental study of (E)-3-(2,6-dichlorophenyl)-acrylamide and its associated dimer were analysed with molecular docking, DFT and QTAIM approach. To spot, describe, and measure the non-covalent interactions (NCIs) of the atoms in the molecules of the monomer and its dimer, some important topological parameters of the charge densities, ρ(r) acquired from the Bader's QTAIM tool are determined, quantitatively. The bond paths are shown to persist for a range of five types of NCIs such as weak conventional (C-H···Cl) and nonconventional (C-O···C and N-O···Cl), medium (N-H···Cl) and strong O-H···O NCIs revealed by the existence of BCPs (ranging from 1.921 - 3.259 Å). A comprehensive explanation of the spectroscopic data like vibrational, electronic, and NMR spectra is reported along with the NLO, reactivity. Hydroxamic acid exhibited an excellent nonlinear optical activity (β₀ = 14.8098 × 10⁻³⁰). To predict the various reactive sites in the molecule, molecular electrostatic potential diagrams were displayed.