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Nanocrystal up-conversion phosphors (UCP), ytterbium-and erbium-codoped lanthanum molybdate (La 2 (MoO 4 ) 3 :Yb,Er), were prepared for the first time for potential uses in bioassays especially in biochip-based analysis. The La 2 (MoO 4 ) 3 :Yb,Er nanocrystals, with an average diameter of 50 nm, were prepared via a hydrothermal method. After being annealed at 800°Cfor 5 h, strong emission of these nanocrystals was observed when excited with a 980 nm infrared (IR) laser. Fluorescent intensity of these nanocrystals is much stronger than that of bulk materials. Down-conversion spectrum of the nanocrystal phosphors was also examined. Two-photon excitation mechanism was proposed for the up-conversion process. Factors affecting the up-conversion fluorescent intensity were also studied. The particlesize-dependent phenomenon was first observed for nanocrystal UCP, and the mechanism was discussed.

␣-Nitrosyl hemoglobin, ␣(Fe-NO) 2 ␤(Fe) 2 , which is frequently observed upon reaction of deoxy hemoglobin with limited quantities of NO in vitro as well as in vivo, has been synthetically prepared, and its reaction with O 2 has been investigation by EPR and thermodynamic equilibrium measurements. ␣-Nitrosyl hemoglobin is relatively stable under aerobic conditions and undergoes reversible O 2 binding at the heme sites of its ␤-subunits. Its O 2 binding is coupled to the structural/functional transition between T-(low affinity extreme) and R-(high affinity) states. This transition is linked to the reversible cleavage of the heme Fe-proximal His bonds in the ␣(Fe-NO) subunits and is sensitive to allosteric effectors, such as protons, 2,3-biphosphoglycerate, and inositol hexaphosphate. In fact, ␣(Fe-NO) 2 ␤(Fe) 2 is exceptionally sensitive to protons, as it exhibits a highly enhanced Bohr effect. The total Bohr effect of ␣-nitrosyl hemoglobin is comparable to that of normal hemoglobin, despite the fact that the oxygenation process involves only two ligation steps. All of these structural and functional evidences have been further confirmed by examining the reactivity of the sulfhydryl group of the Cys ␤93 toward 4,4-dipyridyl disulfide of several ␣-nitrosyl hemoglobin derivatives over a wide pH range, as a probe for quaternary structure. Despite the halved O 2 -carrying capacity, ␣-nitrosyl hemoglobin is fully functional (cooperative and allosterically sensitive) and could represent a versatile low affinity O 2 carrier with improved features that could deliver O 2 to tissues effectively even after NO is sequestered at the heme sites of the ␣-subunits. It is concluded that the NO bound to the heme sites of the ␣-subunits of hemoglobin acts as a negative allosteric effector of Hb and thus might play a role in O 2 /CO 2 transport in the blood under physiological conditions.

Hepatitis B virus (HBV) causes acute and chronic hepatitis and hepatocellular carcinoma. Small interfering RNA (siRNA) and lamivudine have been shown to have anti-HBV effects through different mechanisms. However, assessment of the genome-wide effects of siRNA and lamivudine on HBV-producing cell lines has not been reported, which may provide a clue to interrogate the HBV-cell interaction and to evaluate the siRNA's side effect as a potential drug. In the present study, we designed seven siRNAs based on the conserved HBV sequences and tested their effects on the expression of HBV genes following sorting of siRNA-positive cells. Among these seven siRNAs, siRNA-1 and siRNA-7 were found to effectively suppress HBV gene expression. We further addressed the global gene expression changes in stable HBV-producing cells induced by siRNA-1 and siRNA-7 by use of human genome-wide oligonucleotide microarrays. Data from the gene expression profiling indicated that siRNA-1 and siRNA-7 altered the expression of 54 and 499 genes, respectively, in HepG2.2.15 cells, which revealed that different siRNAs had various patterns of gene expression profiles and suggested a complicated influence of siRNAs on host cells. We further observed that 18 of these genes were suppressed by both siRNA-1 and siRNA-7. Interestingly, seven of these genes were originally activated by HBV, which suggested that these seven genes might be involved in the HBV-host cell interaction. Finally, we have compared the effects of siRNA and lamivudine on HBV and host cells, which revealed that siRNA is more effective at inhibiting HBV expression at the mRNA and protein level in vitro, and the gene expression profile of HepG2.2.15 cells treated by lamivudine is totally different from that seen with siRNA.

Here we report a modular strategy for preparing physically cross-linked and mechanically robust free-standing hydrogels comprising unique thermotropic liquid crystalline (LC) domains and magnetic nanoparticles both of which serve as the physical cross-linkers resulting in hydrogels that can be used as magnetically responsive soft actuators. A series of amphiphilic LC pentablock copolymers of poly(acrylic acid) (PAA), poly(5-cholesteryloxypentyl methacrylate) (PC5MA), and poly(ethylene oxide) (PEO) blocks in the sequence of PAA-PC5MA-PEO-PC5MA-PAA were prepared using reversible addition-fragmentation chain transfer polymerization. These pentablock copolymers served as macromolecular ligands to template Fe(3)O(4) magnetic nanoparticles (MNPs), which were directly anchored to the polymer chains through the coordination bonds with the carboxyl groups of PAA blocks. The resulting polymer/MNP nanocomposites comprised a complicated hierarchical structure in which polymer-coated MNP clusters were dispersed in a microsegregated pentablock copolymer matrix that further contained LC ordering. Upon swelling, the hierarchical structure was disrupted and converted to a network structure, in which MNP clusters were anchored to the polymer chains and LC domains stayed intact to connect solvated PEO and PAA blocks, leading to a free-standing LC magnetic hydrogel (LC ferrogel). By varying the PAA weight fraction (f(AA)) in the pentablock copolymers, the swelling degrees (Q) of the resulting LC ferrogels were tailored. Rheological experiments showed that these physically cross-linked free-standing LC ferrogels exhibit good mechanical strength with storage moduli G' of around 10(4)-10(5) Pa, similar to that of natural tissues. Furthermore, application of a magnetic field induced bending actuation of the LC ferrogels. Therefore, these physically cross-linked and mechanically robust LC ferrogels can be used as soft actuators and artificial muscles. Moreover, this design strategy is a versatile platform for incorporation of different types of nanoparticles (metallic, inorganic, biological, etc.) into multifunctional amphiphilic block copolymers, resulting in unique free-standing hybrid hydrogels of good mechanical strength and integrity with tailored properties and end applications.