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Theoretical Evaluation of Sulfur-Based Reactions as a Model for Biological Antioxidant Defense.

ABSTRACT: Sulfur-containing amino acids, Methionine (Met) and Cysteine (Cys), are very susceptible to Reactive Oxygen Species (ROS). Therefore, sulfur-based reactions regulate many biological processes, playing a key role in maintaining cellular redox homeostasis and modulating intracellular signaling cascades. In oxidative conditions, Met acts as a ROS scavenger, through Met sulfoxide formation, while thiol/disulfide interchange reactions take place between Cys residues as a response to many environmental stimuli. In this work, we apply a QM/MM theoretical-computational approach, which combines quantum-mechanical calculations with classical molecular dynamics simulations to estimate the free energy profile for the above-mentioned reactions in solution. The results obtained, in good agreement with experimental data, show the validity of our approach in modeling sulfur-based reactions, enabling us to study these mechanisms in more complex biological systems.

SUBMITTER: De Sciscio ML

PROVIDER: S-EPMC9741100 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Theoretical Evaluation of Sulfur-Based Reactions as a Model for Biological Antioxidant Defense.

De Sciscio Maria Laura ML D'Annibale Valeria V D'Abramo Marco M

International journal of molecular sciences 20221122 23

Sulfur-containing amino acids, Methionine (Met) and Cysteine (Cys), are very susceptible to Reactive Oxygen Species (ROS). Therefore, sulfur-based reactions regulate many biological processes, playing a key role in maintaining cellular redox homeostasis and modulating intracellular signaling cascades. In oxidative conditions, Met acts as a ROS scavenger, through Met sulfoxide formation, while thiol/disulfide interchange reactions take place between Cys residues as a response to many environmenta ...[more]

PMID: 36498842

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Project description:A new copper(ii) complex, [Cu(LC)(Ibu-phen)(H2O)2](ClO4)2 (LC: lidocaine, Ibu-phen: ibuprofen amide-phenanthroline), was synthesized and characterized. The antioxidant activities of the free ligands and the copper(ii) complex were evaluated by in vitro experiments and theoretical calculations using density functional theory (DFT). Structures of the ligand Ibu-phen and the complex were identified by 1H and 13C NMR, FT-IR spectroscopies, mass spectrometry, thermogravimetric analysis and elemental analysis. The antioxidant potentials of LC and Ibu-phen ligands as well as copper(ii) complex were also evaluated by DPPH˙, ABTS˙+, HO˙ essays and EPR spectroscopy. The experimental results show that the radical scavenging activity (RSA) at various concentrations is decreased in the following order: copper(ii) complex > ascorbic acid > LC > Ibu-phen. Structural and electronic properties of the studied compounds were also analyzed by DFT approach at the M05-2X/6-311++g(2df,2p)//M05-2X/LanL2DZ level of theory. ESP maps and NPA charge distributions show that the highly negative charge regions found on the N and O heteroatoms make these sites more favorable to bind with the central copper ion. Frontier orbital distributions of copper(ii) complex indicate that HOMOs are mainly localized at Ibu-phen, while its LUMOs are distributed at LC. Based on natural bond orbitals (NBO) analyses, Cu(ii) ion plays as electron acceptor in binding with the two ligands and two water molecules. Thermochemical properties including bond dissociation enthalpy (BDE), ionization energy (IE), electron affinity (EA), proton affinity (PA) characterizing three common antioxidant mechanisms i.e. hydrogen transfer (HT), single electron transfer (SET) and proton loss (PL) were finally calculated in the gas phase and water solvent for two ligands and the copper(ii) complex at the same level of theory. As a result, the higher EA and lower BDE and PA values obtained for copper(ii) complex show that the complex shows higher antioxidant potential than the free ligands.

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Theoretical Evaluation of Sulfur-Based Reactions as a Model for Biological Antioxidant Defense.

Publications

Theoretical Evaluation of Sulfur-Based Reactions as a Model for Biological Antioxidant Defense.

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