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Objective To study the anti-oxidation properties of Zn2+-quercetin complexes .Methods The binding stoi-chiometric ratios and the binding constant of Zn2+ to quercetin were measured with UV-Vis spectroscopy .The binding sites on quercetin were determined via1 H NMR spectroscopy .The antioxidant activities of Zn2+-quercetin complexes were compared to quercetin by scavenging DPPH radical method .The binding ratio of Zn2+ to quercetin depends on neutralization of phenol groups of quercetin .Results The binding ratio of Zn2+ to quercetin is 1:2 when less than two OH groups were deprotonated . The binding ratio is 1:1 when more than three OH groups were deprotonated .The apparent binding constant is 2 .42 × 106 M -1 for the 1:1 Zn2+-quercetin complex .The 3′-OH and 4′-OH of quercetin are involved in the Zn2+ binding .The scavenging DPPH radical activity of Zn2+-quercetin complex is 2 .3 times of quercetin .Conclusion These results provide a new insight to expand applications of this traditional Chinese medicine .
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The interaction of baicalein with bovine serum albumin (BSA) was investigated with the help of spec-troscopic and molecular docking studies. The binding affinity of baicalein towards BSA was estimated to be in order of 105 M?1 from fluorescence quenching studies. NegativeΔH° (?5.6670.14 kJ/mol) and positive (ΔS°) ( t 79.96 7 0.65 J/mol K) indicate the presence of electrostatic interactions along with the hydrophobic forces that result in a positiveΔS°. The hydrophobic association of baicalein with BSA di-minishes in the presence of sodium dodecyl sulfate (SDS) due to probable hydrophobic association of baicalein with SDS, resulting in a negativeΔS° ( ? 40.65 7 0.87 J/mol K). Matrix-assisted laser desorption ionization/time of flight (MALDI–TOF) experiments indicate a 1:1 complexation between baicalein and BSA. The unfolding and refolding phenomena of BSA were investigated in the absence and presence of baicalein using steady-state and fluorescence lifetime measurements. It was observed that the presence of urea ruptured the non-covalent interaction between baicalein and BSA. The presence of metal ions (Ag t , Mg2 t , Ni2 t , Mn2 t , Co2 t and Zn2 t ) increased the binding affinity of ligand towards BSA. The changes in conformational aspects of BSA after ligand binding were also investigated using circular di-chroism (CD) and Fourier transform infrared (FT-IR) spectroscopic techniques. Site selectivity studies following molecular docking analyses indicated the binding of baicalein to site 1 (subdomain IIA) of BSA.&2016 Xi'an Jiaotong University. Production and hosting by Elsevier B.V. This is an open access article.
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Objective: To investigate the specific molecular recognition ability for galangin molecular imprinting polymer (GMIP). Methods: GMIP was prepared through the method of thermal polymerization with galangin as template molecular, acrylamide (AM) as functional monomer, ethyleneglycol dimethacrylate (EGDMA) as cross-linker, and tetrahydrofuran, acetonitrile, and acetone as pore forming agents, respectively. The GMIP was characterized by infrared spectroscopy and scanning electron microscopy (SEM). In addition, the GMIP was investigated in equilibrium binding experiment to evaluate its adsorption property and selective recognition. Results: The Scathard model analysis showed that two kinds of binding sites existed in the GMIP. The dissociation constant (Kd) and apparent maximum binding constant (Qmax) were Kd1 = 0.961 mmol/L, Qmax1 = 19.79 μmol/g for high affinity binding sites and Kd2 = 0.101 mmol/L, Qmax2 = 51.09 μmol/g for low affinity binding sites, respectively. Conclusion: GMIP has the specific adsorption and recognition capabilities to the galangin molecules. It can be a novel material for the separation and purification of the active ingredients from natural products.
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An octahedral ruthenium(II) Schiff base complexes of the type [Ru(CO)(Py)L] (L = dianion of the Schiff bases derived from acetoacetanilide with o-phenylenediamine and salicylaldehyde/ohydroxyacetophenone/ o-vanillin/2-hydroxy-1-naphthaldehyde) have been synthesized from the reactions of equimolar ratio of [Ru(CO)(PPh3)2(Py)] and Schiff bases in benzene. The formation of the Schiff base ligands and its complexes have been envisaged from IR, UV-VIS, 1H, 13C, 31P NMR, High resolution mass and Powder XRD studies. These spectral studies confirm an octahedral environment around the metal ion. The redox behaviour of the complexes has also been determined. The ligands, metal precursors and the complexes were tested for their efficiency towards antimicrobial activity. DNA binding studies (Herring Sperm DNA) were carried out for the complexes [Ru(CO)(Py)L1] and [Ru(CO)(Py)L2] using biochemical techniques such as UV-VIS, cyclic voltammetry and differential pulse voltammetry. These techniques paved the way to probe the details of their DNA binding abilities. Intrinsic binding constant have been estimated and it showed a moderate intercalative interactions than the other classical intercalators.
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Capsular polysaccharides (SPS) are an integral component of gram-negative bacteria, and also have potential use as vaccine. In this paper, interactions of SPS isolated from Klebsiella strains K20 and K51 with cationic dyes pinacyanol chloride (PCYN) and acridine orange (AO) were studied by absorbance and fluorescence measurements. Both the polysaccharides having glucuronic acid as the potential anionic site induced strong metachromasy (blue shift ~100 nm) in the PCYN. The spectral changes were studied at different polymer/dye molar ratios (P/D = 0-40). A complete reversal of metachromasy was observed upon addition of co-solvents, suggesting the breakaway of dye molecules from the biopolymer matrix. Binding constant, changes in free energy, enthalpy and entropy of the dye polymer complex were also computed from the spectral data at different temperatures to reveal the nature of the interaction. Quenching of fluorescence of AO by the polymers and the incorporated mechanisms were also explored.