Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples...Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence （PL） and electron paramagnetic resonance （EPR） spectro- scopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 28 = 39° corresponding to secondary phase of CuO （[111] crystalline face） appears when x≤ 6 mol.%. PL spectra of the samples show a strong ultraviolet （UV） emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2＋ ions.展开更多
Amyloid peptide fibrillogenesis induced by Cu（II） ions is a key event in the pathogenesis of Alzheimer＇s disease. Dendrimers have been found to be active in preventing fibril formation. Therefore, they hold promise...Amyloid peptide fibrillogenesis induced by Cu（II） ions is a key event in the pathogenesis of Alzheimer＇s disease. Dendrimers have been found to be active in preventing fibril formation. Therefore, they hold promise for the treatment of Alzheimer＇s disease. In this study, the fibrillation mechanism of amyloid peptide Aβ 1-40 was studied by adding Cu（II） in the absence and presence of 4th generation poly（propyleneimine） glycodendrimer functionalized with sulfate groups, using dynamic light scattering （DLS）, circular dichroism （CD）, fluorescence, electron paramagnetic resonance （EPR） and molecular modeling （MD）. The glycodendrimer was non-toxic to mHippoE-18 embryonic mouse hippocampal cells, selected as a nerve cell model and decreased the toxicity of peptide aggregates formed after the addition of Cu（II）. The binary systems of Cu（II）-glycodendrimer, Cu（II）-peptide, and glycodendrimer-peptide were first characterized. At the lowest Cu（II）/glycodendrimer molar ratios, Cu（II） was complexed by the internal-dendrimer nitrogen sites. After saturation of these sites, Cu（II） binding with sulfate groups occurred. Stable Cu（II）-peptide complexes formed within 5 min and were responsible for a transition from an α helix to a β-sheet conformation of Aβ 1-40. Glycodendrimer-peptide interactions provoked the stabilization of the a-helix, as demonstrated in the absence of Cu（II） by the Thioflavin T assay, and in the presence of Cu（II） by CD, EPR, and MD. Formation of fibrils is differentially modulated by glycodendrimer and Cu（II） concentrations for a fixed amount of Aβ 1-40. Therefore, this multidisciplinary study facilitated the recognition of optimal experimental conditions that allow the glycodendrimer to avoid the fibril formation induced by Cu（II）.展开更多
文摘Nanocrystalline Zn1_xCuxO （x = 0, 0.02, 0.04, 0.06, 0.08） samples were synthesized by a novel auto-combustion method using glycine as the fuel material. The structural, optical and magnetic properties of the samples were characterized using XRD, SEM, photoluminescence （PL） and electron paramagnetic resonance （EPR） spectro- scopies. The XRD spectra of samples reveal the hexagonal wurtzite structures of ZnO. As the copper content increases, a diffraction peak at 28 = 39° corresponding to secondary phase of CuO （[111] crystalline face） appears when x≤ 6 mol.%. PL spectra of the samples show a strong ultraviolet （UV） emission and defect related visible emissions. Cu-doping in ZnO can effectively adjust the energy level in ZnO, which leads to red shift in the emission peak position in UV region. The EPR spectra of Cu-doped ZnO nanoparticles show a distinct and broad signal at room temperature, suggesting that it may be attributed to the exchange interactions within Cu2＋ ions.
文摘Amyloid peptide fibrillogenesis induced by Cu（II） ions is a key event in the pathogenesis of Alzheimer＇s disease. Dendrimers have been found to be active in preventing fibril formation. Therefore, they hold promise for the treatment of Alzheimer＇s disease. In this study, the fibrillation mechanism of amyloid peptide Aβ 1-40 was studied by adding Cu（II） in the absence and presence of 4th generation poly（propyleneimine） glycodendrimer functionalized with sulfate groups, using dynamic light scattering （DLS）, circular dichroism （CD）, fluorescence, electron paramagnetic resonance （EPR） and molecular modeling （MD）. The glycodendrimer was non-toxic to mHippoE-18 embryonic mouse hippocampal cells, selected as a nerve cell model and decreased the toxicity of peptide aggregates formed after the addition of Cu（II）. The binary systems of Cu（II）-glycodendrimer, Cu（II）-peptide, and glycodendrimer-peptide were first characterized. At the lowest Cu（II）/glycodendrimer molar ratios, Cu（II） was complexed by the internal-dendrimer nitrogen sites. After saturation of these sites, Cu（II） binding with sulfate groups occurred. Stable Cu（II）-peptide complexes formed within 5 min and were responsible for a transition from an α helix to a β-sheet conformation of Aβ 1-40. Glycodendrimer-peptide interactions provoked the stabilization of the a-helix, as demonstrated in the absence of Cu（II） by the Thioflavin T assay, and in the presence of Cu（II） by CD, EPR, and MD. Formation of fibrils is differentially modulated by glycodendrimer and Cu（II） concentrations for a fixed amount of Aβ 1-40. Therefore, this multidisciplinary study facilitated the recognition of optimal experimental conditions that allow the glycodendrimer to avoid the fibril formation induced by Cu（II）.
