Cunwang Ge

Binding of dihydromyricetin to human hemoglobin: Fluorescence and circular dichroism studies

The binding reaction between dihydromyricetin (DMY) and human hemoglobin (HHb) was investigated systematically with various spectroscopic methods including fluorescence quenching technique, ultraviolet (UV)-vis absorption, synchronous fluorescence, circular dichroism (CD) spectroscopy. The experimental results showed that DMY effectively quenched the intrinsic fluorescence of HHb via static quenching. DMY binds to HHb with a stoichiometry that varies from 0.972:1 to 0.906:1 as the temperature increases from 296 to 304 K. The DMY-HHb binding constants were determined to be K(296)=2.79 × 10(4) and K(304)=1.18 × 10(4) Lmol(-1). The reaction is characterized by negative enthalpy (ΔH=-80.46 kJ mol(-1)) and negative entropy (ΔS=-186.72 kJ mol(-1)), indicating that the predominant forces in the DMY-HHb complex are van der Waals and hydrogen bonding forces. Based on the Försters theory of non-radiative energy transfer, the binding distance between DMY and the inner tryptophan residues of HHb was determined to be 3.15 nm. Furthermore, the CD spectroscopy indicated the secondary structure of HHb is not changed in the presence of DMY.

Surface Reconstruction for Preparation of Plasmonic Au/TiO2 Nanoparticle with Perfect Hetero Interface and Improved Photocatalytic Capacity

The photocatalytic activity of plasmonic Au/TiO2 nanoparticles (NPs) is dependent on distances between Au and TiO2. The preparation of plasmonic NPs is still a challenge because of an inherent lattice mismatch on heterogeneous interfaces. The combination between Au and TiO2 NPs often exhibits physical adsorption, which affect block the electron transferring process by photo-induction from TiO2 to Au NPs and weaken the photocatalytic activity. In this work an approach for preparing plasmonic Au/TiO2 NPs with perfect hetero-interface was proposed based on reconstruction of anatase TiO2 with (101) surface and in-situ reduction of Au NPs. Under UV-irradiation, anatase TiO2 NPs with a high percentage of (001) facets in formaldehyde solution undergo photochemical reactions to reconstruct the (101) surface of TiO2 and simultaneously allow polyformaldehyde to absorb on the same surface. Thus, Au(OH)-4 ions could be adsorbed on the (101) surfaces of TiO2 through electrostatic adsorption and reduced to form nano-Au in situ after recrystallization at 180 °C. The high-resolution transmission electron microscopy (HRTEM) images showed clear nanoscale lattice transition on heterogeneous interfaces of Au/TiO2 NPs. The surface structure of TiO2 NPs and the growth mechanism of Au/TiO2 NPs were evaluated with HRTEM, X-ray photoelectron spectra (XPS) and Fourier transform infrared spectroscopy (FTIR). It was demonstrated that the as-prepared plasmonic Au/TiO2 NPs had higher photocatalytic activity and corrosion resistance in comparison with primary TiO2 NPs by photo-electrochemical measurements. The reinforcing mechanism could be interpreted with Mott-Schottky analysis in terms of quantum mechanics. Our study implied that the reconstruction based synthesis may open up more opportunities to obtain lattice-mismatch nanomaterials for photocatalysis.