2 research outputs found

    Screening and unveiling antibacterial mechanism of dandelion phenolic extracts against <i>Staphylococcus aureus</i> by inhibiting intracellular Na<sup>+</sup>–K<sup>+</sup> ATPase based on molecular docking and molecular dynamics simulation

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    Staphylococcus aureus is one of the most frequently food-contaminated incidence of healthcare-associated Gram-positive bacteria. The antibacterial function and mechanism of phenolic compounds from dandelion are still unclear. Herein, this work aims to screen one of dandelion phenolic extracts with the strongest antibacterial function from its organ such as flower, stem, leaf and root, and to reveal its antibacterial mechanism. The results indicated dandelion flower phenolic extract (DFPE) containing the highest content of caffeic acid, followed by luteolin and luteolin-7-O-glucoside. They, especially caffeic acid and luteolin-7-O-glucoside, played a key role in making the bacterial cellular-membrane ruptured against the bacteria. The leakage of the intracellular substances (adenosine triphosphate and Na+–K+ ATPase) was further confirmed. Conventional hydrogen bond, pi-anion, pi-alkyl were involved in the interaction between caffeic acid or luteolin-7-O-glucoside and Na+–K+ ATPase. Additionally, the dynamic equilibrium of the liganded ATPase complex were achieved after 105 ns, and the lower values from the radius of gyration and solvent accessible surface area in the complex demonstrated the highly tight and compact structure of the liganded protein. The highest free binding energy (ΔGbind = −47.80 kJ/mol) between Na+–K+ ATPase and luteolin-7-O-glycloside was observed. Overall, DFPE can be used as an effective anti-bacterial agent due to the contribution of its bioactive ingredients such as caffeic acid and luteolin-7-O-glucoside for membrane-breaking. Communicated by Ramaswamy H. Sarma</p

    Biosurfactant–Protein Interaction: Influences of Mannosylerythritol Lipids‑A on β‑Glucosidase

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    In this work, the influences of a biosurfactant, mannosylerythritol lipids-A (MEL-A) toward β-glucosidase activity and their molecular interactions were studied by using differential scanning calorimetry (DSC), circular dichroism spectroscopy (CD), isothermal titration calorimetry (ITC), and docking simulation. The enzyme inhibition kinetics data showed that MEL-A at a low concentration (< critical micelle concentration (CMC), 20.0 ± 5.0 μM) enhanced β-glucosidase activity, whereas it inhibited the enzyme activity at higher concentrations more than 20.0 μM, followed by a decreased <i>V</i><sub>max</sub> and <i>K</i><sub>m</sub> of β-glucosidase. The thermodynamics and structural data demonstrated that the midpoint temperature (<i>T</i><sub>m</sub>) and unfolding enthalpy (Δ<i><i>H</i></i>) of β-glucosidase was shifted to high values (76.6 °C, 126.3 J/g) in the presence of MEL-A, and the secondary structure changes of β-glucosidase, including the increased α-helix, β-turn, or random coil contents, and a decreased β-sheet content were caused by MEL-A at a CMC concentration. The further ITC and docking simulations suggested the bindings of MEL-A toward β-glucosidase were driven by weak hydrophobic interactions happened between the amino acid residues of β-glucosidase and the fatty acid residues of MEL-A, in addition to hydrogen bonds between amino acids and hydroxyl in glycosyl residues of this biosurfactant
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