MEASUREMENT OF NANOMETER SCALE CADMIUM SELENIDE NANOCRYSTALS AND CLUSTER MOLECULES

High performance Dynamic Light Scattering (DLS) has been used to determine the hydrodynamic di-ameters of CdSe nanocrystals as well as CdSe cluster molecules in a size range of 1 to 10 nm (Eichh鰂er et al., 2001). The method enables the determination of their particle size, including their ligand shells, in solution. The results are consistent with the blue shift of the absorption bands, as well as Transmission Electron Microscope (TEM) experiments. The sizes of the cluster molecules were estimated from space filling models constructed from the results of a single crystal X-ray structure determination. DLS gave comparable results for the size of both types of compound, indicating that it is potentially an important additional measurement technique to TEM, which uses harsh measurement conditions, and to powder X-ray diffraction, which is difficult to interpret below 5 nm.

Efficiently Adsorbing CO Molecules Using Al_6Si Cluster

Based on the density functional theory with generalized gradient approximation, the stable geometrical structures of one or more CO molecules adsorbed on the Al6Si cluster are investigated and the corresponding adsorption energies are also calculated. It is found that the cluster Al6Si can adsorb six CO molecules. The thermal stability of the（CO）6@Al6Si complexes is examined using the atom centered density matrix propagation molecular dynamics calculations at 373 K. The results show that two isomers of Al6Si cluster can solidly adsorb six CO molecules, and the other isomer adsorbs four ones. Therefore, the Al6Si cluster is a promising candidate for eliminating CO effectively.

CD200 Attenuates Methamphetamine-induced Microglial Activation and Dopamine Depletion

This study examined the neuroprotective effect of cluster of differentiation molecule 200 （CD200） against methamphetamine （METH）-induced neurotoxicity. In the in vitro experiment, neuron-microglia cultures were treated with METH （20 μmol/L）, METH （20 μmol/L）＋CD200-Fc （10 μg/mL） or CD200-Fc （10 μg/mL）. Those untreated served as control. Microglia activation expressed as the ratio of MHC-Ⅱ/CD11b was assessed by flow cytometry. The cytokines （IL-1β, TNF-α） secreted by activated microglia were detected by enzyme-linked immunosorbent assay （ELISA）. In the in vivo experiment, 40 SD rats were divided into control, METH, METH＋CD200-Fc and CD200-Fc groups at random. Rats were intraperitoneally injected with METH （15 mg/kg 8 times at 12 h interval） in METH group, with METH （administered as the same dose and time as the METH group） and CD200-Fc （1 mg/kg at day 0, 2, 4 after METH injection） in METH＋CD200-Fc group, with CD200-Fc （1 mg/kg injected as the same time as the METH＋CD200-Fc group） or with physiological saline solution in the control group. The level of striatal dopamine （DA） in rats was measured by high-performance liquid chromatography （HPLC）. The microglial cells were immunohistochemically detected for the expression of Iba-1, a marker for microglial activation. The results showed that METH could increase the microglia activation in the neuron-microglia cultures and elevate the secretion of IL-1β and TNF-α, which could be attenuated by CD200-Fc. Moreover, CD200-Fc could partially reverse the striatal DA depletion induced by METH and reduce the number of activated microglia, i.e. Iba-1-positive cells. It was concluded that CD200 may have neuroprotective effects against METH-induced neurotoxicity by inhibiting microglial activation and reversing DA depletion in striatum.