Characterization of the binding of shikonin to human immunoglobulin using scanning electron microscope, molecular modeling and multi-spectroscopic methods

Molecular Assessment of the Toxic Mechanism of the Latest Neonicotinoid Dinotefuran with Glutathione Peroxidase 6 from Arabidopsis thaliana

With widespread applications of the latest neonicotinoid in agriculture, dinotefuran has gradually become a hazardous contaminant for plants through the generation of excessive reactive oxygen species. However, the potential toxic mechanisms of oxidative damages to plants induced by dinotefuran are still unknown. As a core component of the glutathione antioxidant enzyme system, glutathione peroxidases have been used as biomarkers to reflect excessive oxidative stress. In this study, the hazardous effects of dinotefuran on AtGPX6 were investigated at the molecular level. The intrinsic fluorescence intensity of AtGPX6 was quenched using the static quenching mechanism upon binding with dinotefuran. Moreover, a single binding site was predicted for AtGPX6 toward dinotefuran, and the complex formation was presumed to be driven by hydrogen bonds or van der Waals forces, which conformed with the molecular docking results. In addition, AtGPX6 exhibited moderate binding affinity with dinotefuran based on the bio-layer interferometry assay. In addition, the loosening and unfolding of the protein skeleton of AtGPX6 with the addition of dinotefuran were explored along with the increase of hydrophobicity around tryptophan residues. Lastly, the toxic effects of dinotefuran on the root growth of Arabidopsis seedlings were also examined. The exploration of the binding mechanism of dinotefuran with AtGPX6 at the molecular level would provide the toxicity assessment of dinotefuran on plants.

Molecular docking explores heightened immunogenicity and structural dynamics of acetaldehyde human immunoglobulin G adduct

Acetaldehyde is a metabolite of ethanol, an important constituent of tobacco pyrolysis and the aldehydic product of lipid peroxidation. Acetaldehyde induced toxicity is mainly due to its binding to cellular macromolecules resulting in the formation of stable adducts accompanied by oxidative stress. The aim of this study was to characterize structural and immunological alterations in human immunoglobulin G (IgG) modified with acetaldehyde in the presence of sodium borohydride, a reducing agent. The IgG modifications were studied by various physicochemical techniques such as fluorescence and CD spectroscopy, free amino group estimation, 2,2-azobis 2-amidinopropane (AAPH) induced red blood cell hemolysis as well as transmission electron microscopy. Molecular docking was also employed to predict the preferential binding of acetaldehyde to IgG. The immunogenicity of native and acetaldehyde-modified IgG was investigated by immunizing female New Zealand white rabbits using native and modified IgG as antigens. Binding specificity and cross reactivity of rabbit antibodies was screened by competitive inhibition ELISA and band shift assays. The modification of human IgG with acetaldehyde results in quenching of the fluorescence of tyrosine residues, decrease in free amino group content, a change in the antioxidant property as well as formation of cross-linked structures in human IgG. Molecular docking reveals strong binding of IgG to acetaldehyde. Moreover, acetaldehyde modified IgG induced high titer antibodies (>1:12800) in the experimental animals. The antibodies exhibited high specificity in competitive binding assay toward acetaldehyde modified human IgG. The results indicate that acetaldehyde induces alterations in secondary and tertiary structure of IgG molecule that leads to formation of neo-epitopes on IgG that enhances its immunogenicity.

Inhibiting effects of common trivalent metal ions on transmembrane-type 2 matrix metalloproteinase

Transmembrane-type 2 matrix metalloproteinase (MT2-MMP) degrades connective extracellular matrix between cells and enables tumor cells to migrate and metastasize, making this substance a potential therapeutic target in various diseases. In this work, the interactions between MT2-MMP and common trivalent metal ions, including aluminum (Al³⁺) and ferrum (Fe³⁺) ions, were investigated. Enzymatic detection revealed that Al³⁺ and Fe³⁺ strongly inhibited the MT2-MMP. Fluorescence spectrography elucidated a static quenching interaction between the negatively charged amino acids on MT2-MMP and the inhibitory trivalent metal ions, indicating that a stable complex was formed between MT2-MMP and metal ions. In addition, fluorescence data and molecular modeling analysis of the binding characteristics revealed that one trivalent metal ion bound with a protein in the stable complex formation process. The potential inhibitory effect of Al³⁺ on MT2-MMP was further examined in an MT2-MMP-overexpressed cell line, HT1080, by using flow cytometry. As a result, Al³⁺ can promote HT1080 cell apoptosis in a micromolar concentration-dependent manner. This work illustrated that common trivalent metal ions can potentially inhibit MT2-MMP-related tumors.