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Md. Abdur Razzak,이지은,박희호,박태현,최신식 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.5
The curry compound, curcumin exerts multiple health-promotive functions; however, its poor solubility and stability limits its biological applications. In this study, we illuminate intermolecular binding mechanisms in the nano-sized complex of curcumin with silkworm protein, 30Kc19. The intrinsic fluorescence of 30Kc19 was gradually quenched by the increase of curcumin concentrations, which demonstrates molecule-molecule complexations mediated by the fluorophore amino acid residues (Tyr, Trp) in the protein. The fluorescence quenching showed that the binding occurred at 1:1 molar ratio with binding constant of 3.28 × 104 M-1. The results from scanning electron microscopy and dynamic light scattering indicate that the complexes were formed with cubicle shapes and sizes of 200-250 nm at pH 8.0 (zeta-potential < −20 mV). Along with Fourier transform infrared analysis, computational studies of protein-ligand docking simulation suggest a mechanism that curcumin and 30Kc19 forms complexes through specific amino acid residues (Trp174, Trp180, and Trp225) with minimum binding distance (4 Å). The complexation of curcumin with 30Kc19 protein effectively suppressed the degradation of curcumin over 10 h and improved its antioxidant activity up to 30%. These findings suggest an application of 30Kc19 for the delivery of waterinsoluble bioactive medicines.
Structural insights into the binding behavior of isoflavonoid glabridin with human serum albumin
Razzak, Md. Abdur,Lee, Ji Eun,Choi, Shin Sik Elsevier 2019 Food hydrocolloids Vol.91 No.-
<P><B>Abstract</B></P> <P>Glabridin (GB), a prenylated isoflavonoid in licorice root has been used as foods and medicines with beneficial biological activities. Human serum albumin (HSA) is the most abundant blood plasma protein binding and transporting ligands such as GB. The present study investigated the interaction between GB and HSA using multi-spectroscopic and molecular docking techniques. Fluorescence spectroscopy demonstrated that GB strongly quenched the tryptophan fluorescence emission of HSA, suggesting that GB-HSA interaction followed a static mode of quenching with a binding constant (K, 10<SUP>5</SUP>-10<SUP>4</SUP> M<SUP>−1</SUP>, 25-37 °C) reflecting strong-to-moderate affinity of GB to HSA. Molecular displacement and protein-ligand docking simulations showed that the probable GB-binding positions of HSA exist near the site I of HSA. The hydrophobic interaction is a dominant binding force for forming GB-HSA complexes, and the binding resulted in conformational changes of HSA protein with more β-sheet structures. Furthermore, the complex formation of GB with HSA changed the hydrodynamic size and zeta-potential of HSA with enhanced solubility of GB. The elucidation of GB-HSA binding behavior will provide insights into the application of GB in food and pharmaceutical industries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Binding of glabridin to human serum albumin was demonstrated by spectroscopy and molecular docking simulation. </LI> <LI> Interaction of glabridin with human serum albumin belongs to static quenching. </LI> <LI> Glabridin binds to the site I of human serum albumin through hydrophobic interactions. </LI> <LI> Glabridin binding changes the structure of human serum albumin with more β-sheets. </LI> <LI> Aqueous solubility of glabridin was enhanced by complexation with human serum albumin. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>