Showing papers by "Hong Liu published in 2012"

Development of Cell-Active N6-Methyladenosine RNA Demethylase FTO Inhibitor

Abstract: The direct nucleic acid repair dioxygenase FTO is an enzyme that demethylates N6-methyladenosine (m6A) residues in mRNA in vitro and inside cells. FTO is the first RNA demethylase discovered that also serves a major regulatory function in mammals. Together with structure-based virtual screening and biochemical analyses, we report the first identification of several small-molecule inhibitors of human FTO demethylase. The most potent compound, the natural product rhein, which is neither a structural mimic of 2-oxoglutarate nor a chelator of metal ion, competitively binds to the FTO active site in vitro. Rhein also exhibits good inhibitory activity on m6A demethylation inside cells. These studies shed light on the development of powerful probes and new therapies for use in RNA biology and drug discovery.

Synthesis, characterization and photocatalytic performance of novel visible-light-induced Ag/BiOI

Abstract: For the first time, a series of Ag/BiOI photocatalysts with different Ag contents have been synthesized by a hydrothermal combinated with photodeposition method. The as-prepared products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), and photoluminescence (PL) emission spectroscopy. The photocatalytic activities of these Ag/BiOI composites under visible-light irradiation (λ > 420 nm) were evaluated by the degradation of acid orange II, methyl orange (MO) and rhodamine B (RB). The results revealed that the Ag/BiOI composites exhibited much higher photocatalytic activities than pure BiOI. The Ag amount in the Ag/BiOI composites played an important role in the corresponding photocatalytic properties and the optimized ratio was obtained at 0.6%. The significant enhancement in the Ag/BiOI photoactivity could be ascribed to both the effect of Ag deposits by acting as electron traps and the surface plasma resonance effect of Ag.

Enhancing the electrochemical performance of lithium ion batteries using mesoporous Li3V2(PO4)3/C microspheres

Abstract: Mesoporous Li3V2(PO4)3–carbon (LVP-C) microspheres are synthesized using Baker's yeast cells as both mesoporous structure templates and amorphous carbon sources. We find that the vanadium cations are combined with the negatively charged hydrophilic groups and are self-assembled both on the yeast cell wall surface and inside the cell by electrostatic interaction and metabolism regulation, respectively. The self-assembly leads to the formation of LVP-C microspheres with diameters of 1–8 μm. These microspheres are composed of densely aggregated nanoparticles (20–40 nm) as well as interconnected nanopores (2–15 nm), and hence they are of mesoporous nature. The nanoparticles can be easily brought into contact with electrolyte, and the open mesoporous structure allows lithium ions to easily penetrate into the microspheres. The carbon network (16.4 wt.%) on the surface of the Li3V2(PO4)3 nanoparticles facilitates electron diffusion. The mesoporous LVP-C microspheres have a high discharge capacity (about 126.7 mAh g−1), only 2% capacity loss of the initial value at the 50th cycle at a current density of 0.2 C, and a high rate capacity of 100.5 mAh g−1 at 5 C in the region of 3.0–4.3 V. The apparent Li+ diffusion coefficient is found to be 6.76 × 10−10 cm2 s−1. The microspheres could be an ideal cathode-active material that fulfills the requirements of rechargeable lithium batteries for high power applications.

In situ synthesis and thermal, tribological properties of thermosetting polyimide/graphene oxide nanocomposites

Abstract: The full exfoliation graphene oxide (GO) nanosheets were synthesized by an improved Hummers’ method. The phenylethynyl terminated thermosetting polyimide (PI) and PI/GO nanocomposites were prepared via a polymerization of monomer reactants process. Thermogravimetric analysis indicated that the incorporation of GO increased the thermal stability of the PI at low filling content. The friction and wear testing results of the PI and PI/GO nanocomposites under dry sliding condition against GCr15 steel showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The friction and wear properties of the PI and PI/GO nanocomposites were investigated on a model ring-on-block test rig under dry sliding conditions against the GCr15 steel. Experimental results showed that the addition of GO evidently improved the friction and wear properties of PI, which were considered to be the result of the formation of uniform transfer film and the increasing of load-carrying capacity. The optimum GO content of nanocomposite for tribological properties is 3 wt%, which could be a potential candidate for tribo-material under dry sliding condition against GCr15 steel.

Bone repair by periodontal ligament stem cellseeded nanohydroxyapatite-chitosan scaffold.

Abstract: Background A nanohydroxyapatite-coated chitosan scaffold has been developed in recent years, but the effect of this composite scaffold on the viability and differentiation of periodontal ligament stem cells (PDLSCs) and bone repair is still unknown. This study explored the behavior of PDLSCs on a new nanohydroxyapatite-coated genipin-chitosan conjunction scaffold (HGCCS) in vitro as compared with an uncoated genipin-chitosan framework, and evaluated the effect of PDLSC-seeded HGCCS on bone repair in vivo. Methods Human PDLSCs were cultured and identified, seeded on a HGCCS and on a genipin-chitosan framework, and assessed by scanning electron microscopy, confocal laser scanning microscopy, MTT, alkaline phosphatase activity, and quantitative real-time polymerase chain reaction at different time intervals. Moreover, PDLSC-seeded scaffolds were used in a rat calvarial defect model, and new bone formation was assessed by hematoxylin and eosin staining at 12 weeks postoperatively. Results PDLSCs were clonogenic and positive for STRO-1. They had the capacity to undergo osteogenic and adipogenic differentiation in vitro. When seeded on HGCCS, PDLSCs exhibited significantly greater viability, alkaline phosphatase activity, and upregulated the bone-related markers, bone sialoprotein, osteopontin, and osteocalcin to a greater extent compared with PDLSCs seeded on the genipin-chitosan framework. The use of PDLSC-seeded HGCCS promoted calvarial bone repair. Conclusion This study demonstrates the potential of HGCCS combined with PDLSCs as a promising tool for bone regeneration.

Identification of IL18RAP/IL18R1 and IL12B as leprosy risk genes demonstrates shared pathogenesis between inflammation and infectious diseases.

Abstract: Of eight leprosy susceptibility loci identified by genome-wide association studies, five have been implicated in Crohn disease, suggesting a common genetic fingerprint between leprosy and inflammatory bowel disease (IBD). Here, we conducted a multiple-stage genetic association study of 133 IBD susceptibility loci in multiple leprosy samples (totaling 4,971 leprosy cases and 5,503 controls) from a Chinese population and discovered two associations at rs2058660 on 2q12.1 (p = 4.57 × 10−19; odds ratio [OR] = 1.30) and rs6871626 on 5q33.3 (p = 3.95 × 10−18; OR = 0.75), implicating IL18RAP/IL18R1 and IL12B as susceptibility genes for leprosy. Our study reveals the important role of IL12/IL18-mediated transcriptional regulation of IFN-γ production in leprosy, and together with previous findings, it demonstrates the shared genetic susceptibility between infectious and inflammatory diseases.

Recent Advances in Neuraminidase Inhibitor Development as Anti-influenza Drugs

Abstract: The recent emergence of the highly pathogenic H5N1 subtype of avian influenza virus (AIV) and of the new type of human influenza A (H1N1) have emphasized the need for the development of effective anti-influenza drugs. Presently, neuraminidase (NA) inhibitors are widely used in the treatment and prophylaxis of human influenza virus infection, and tremendous efforts have been made to develop more potent NA inhibitors to combat resistance and new influenza viruses. In this review, we discuss the structural characteristics of NA catalytic domains and the recent developments of new NA inhibitors using structure-based drug design strategies. These drugs include analogues of zanamivir, analogues of oseltamivir, analogues of peramivir, and analogues of aromatic carboxylic acid and present promising options for therapeutics or leads for further development of NA inhibitors that may be useful in the event of a future influenza pandemic.

Microstructure and type IV cracking behavior of HAZ in P92 steel weldment

Abstract: The creep rupture behavior and microstructure changes of W strengthened P92 steel weld joints have been investigated at 873 K, 898 K and 923 K. The joints were prepared by submerged arc welding (SAW). The results showed that low ductility type IV fracture took place more easily at higher temperature and lower stress. There would be a critical Larson–Miller parameter (LMP) of 35.5 and a critical applied stress of 120 MPa for type IV fracture. The critical stress was independent of creep temperature. Type IV cracks occurred in the fine grained heat affected zone (FGHAZ), corresponding to the maximum heating temperature just above A c3 , which showed the fine equiaxed microstructure without lath structure and the lowest hardness due to the instability of microstructure. An increased number density of Laves phases precipitated on grain boundaries in FGHAZ compared with other zones of weldment during creep, while the coarsening of M 23 C 6 carbides was not very significant in W strengthened P92 steel. The fracture location in FGHAZ exhibited the most severe creep damage among the various zones of weldment and many cavities formed at the grain boundaries during creep. It was considered that the coarse Laves phase at the grain boundaries acted as the preferential cavity nucleation sites. We believe that the degradation of lath substructure and fast formation of Laves phase may be the main metallurgical factors for the type IV cracking.

Synthesis of Monodispersed Spherical Yttrium Aluminum Garnet (YAG) Powders by a Homogeneous Precipitation Method

Abstract: Monodispersed yttrium aluminum garnet (YAG) powders have been synthesized via homogeneous precipitation method from the mixed solutions of yttrium nitrate, aluminum nitrate, and ammonium aluminum sulfate using urea as the precipitant. The molar ratio of aluminum nitrate to ammonium aluminum sulfate has a significant effect on morphology and particle size of the precursor powders. It was found that spherical precursor particles can be obtained when the ratio is 1:1. During the homogeneous precipitation process, aluminum ions precipitate first and form monodispered spherical powders, and then yttrium ions precipitate onto the surface of the existing spheres. Monodispersed spherical YAG particles with 500 nm in diameter were obtained by calcining the precursor powder at 1100°C for 5 h. The so-prepared monodispersed spherical Nd:YAG powders have good sinterability, and can be sintered into transparent ceramics by vacuum sintering at 1650°C for 3.5 h.

One-pot synthesis of nitrogen-doped TiO2 nanorods with anatase/brookite structures and enhanced photocatalytic activity

Abstract: Nitrogen doping in combination with a heterostructure can not only modify the band structure of TiO2 to make it more responsive to visible light, but also suppress charge recombination and lead TiO2 to have enhanced photocatalytic activity as compared to P25. Also, one-dimensional TiO2 nanostructures can serve as electron highways for efficient charge separation and, hence, increase the lifetime of charge carriers and enhance the efficiency of interfacial charge transfer to the adsorbed substrate. In this paper, a simple one-pot synthetic strategy has been designed for preparing TiO2 nanorods with good crystallinity, nitrogen doping and anatase/brookite binary structure characters, using N2H4·H2O as an in situ nitrogen doping source. The physicochemical properties of the catalysts can be tuned by simply changing the concentration ratios of N2H4·H2O to TiO2 colloids. The synergistic effect of nitrogen doping in association with a one-dimensional and anatase/brookite binary structure is suggested to account for the higher catalytic activity of the TiO2 nanorods for decomposing methyl orange and 4-chlorophenol compared to the nanoparticle counterparts under UV and/or visible light illumination.

In situ construction of a titanate–silver nanoparticle–titanate sandwich nanostructure on a metallic titanium surface for bacteriostatic and biocompatible implants

Abstract: A synthetic approach has been developed to in situ construct a new hierarchical nanostructure as an ideal biocompatible and bacteriostatic implant. A highly porous nano-network made of sodium titanate is first formed on the titanium surface by hydrothermal treatment. Silver ions are then inserted between the layered titanate lattices to form silver titanate via ion-exchange with sodium ions. Finally, silver ions are reduced by glucose, leading to the in situ growth of Ag nanoparticles that are sandwiched between layer-structured hydrogen titanate. The amount and the size of the Ag nanoparticles in the titanate–Ag nanoparticles–titanate sandwich can be adjusted by the concentrations of both the AgNO3 and the glucose solutions. The test results show that the silver ions are completely leached from silver titanate after 7 days of immersion in an aqueous solution. In contrast, the Ag ions continue to be released from the titanate–Ag nanoparticle–titanate sandwich nanostructure after 15 days. This steady and prolonged release characteristic is helpful to the long-standing antibacterial process for prevention of severe infection after surgery. A series of antimicrobial and biocompatible tests have shown that the sandwich nanostructure with a low level of silver loading exhibits a bacteriostatic rate as high as 99.99% while retaining low toxicity against cells. The titanate–Ag nanoparticle–titanate sandwich nanostructure, which is fabricated with a low-cost surface modification method, is a promising implantable material that will find applications in artificial bones, joints and dental implants.

UV-visible-light-activated photocatalysts based on Bi2O3/Bi4Ti3O12/TiO2 double-heterostructured TiO2 nanobelts

Abstract: Surface engineering of TiO2 nanobelts by the controlled assembly of functional heterostructures represents an effective approach for the synthesis of high-performance photocatalysts. In this study, we prepared a novel Bi2O3/Bi4Ti3O12/TiO2 double-heterostructured nanobelt by depositing bismuth hydroxide onto the TiO2 nanobelt surface. A thermal annealing treatment led to the formation of a Bi4Ti3O12 interlayer that functioned as a bridge to link Bi2O3 and TiO2. The double-heterostructured TiO2 nanobelts exhibited better UV light photocatalytic performance than commercial P25. Importantly, the photocatalytic activity in the visible range was markedly better than that of Bi2O3 and Bi2O3/TiO2 heterostructured TiO2 nanobelts. The enhanced performance was accounted for by the material band structures where the matching was improved by the unique interlayer.

Inhibition of GPR40 protects MIN6 β cells from palmitate-induced ER stress and apoptosis.

Abstract: Chronic exposure to elevated concentration of free fatty acids (FFA) has been verified to induce endoplasmic reticulum (ER) stress, which leads to pancreatic β-cell apoptosis As one of the medium and long chain FFA receptors, GPR40 is highly expressed in pancreatic β cells, mediates both acute and chronic effects of FFA on β-cell function, but the role of GPR40 in FFA-induced β-cell apoptosis remains unclear In this study, we investigated the possible effects of GPR40 in palmitate-induced MIN6 β-cell apoptosis, and found that DC260126, a novel small molecular antagonist of GPR40, could protect MIN6 β cells from palmitate-induced ER stress and apoptosis Similar results were observed in GPR40-deficient MIN6 cells, indicating that palmitate-induced β-cell apoptosis is at least partially dependent on ER stress pathway via GRP40

Free-standing 3D polyaniline-CNT/Ni-fiber hybrid electrodes for high-performance supercapacitors.

Abstract: Free-standing 3D macroscopic polyaniline (PANi)–carbon nanotube (CNT)–nickel fiber hybrids have been developed, and they deliver high specific capacitance (725 F g−1 at 0.5 A g−1) and high energy density at high rates (∼22 W h kg−1 at 2000 W kg−1, based on total electrode mass) with good cyclability.

HRS1 acts as a negative regulator of abscisic acid signaling to promote timely germination of Arabidopsis seeds

Abstract: In this work, we conducted functional analysis of Arabidopsis HRS1 gene in order to provide new insights into the mechanisms governing seed germination. Compared with wild type (WT) control, HRS1 knockout mutant (hrs1-1) exhibited significant germination delays on either normal medium or those supplemented with abscisic acid (ABA) or sodium chloride (NaCl), with the magnitude of the delay being substantially larger on the latter media. The hypersensitivity of hrs1-1 germination to ABA and NaCl required ABI3, ABI4 and ABI5, and was aggravated in the double mutant hrs1-1abi1-2 and triple mutant hrs1-1hab1-1abi1-2, indicating that HRS1 acts as a negative regulator of ABA signaling during seed germination. Consistent with this notion, HRS1 expression was found in the embryo axis, and was regulated both temporally and spatially, during seed germination. Further analysis showed that the delay of hrs1-1 germination under normal conditions was associated with reduction in the elongation of the cells located in the lower hypocotyl (LH) and transition zone (TZ) of embryo axis. Interestingly, the germination rate of hrs1-1 was more severely reduced by the inhibitor of cell elongation, and more significantly decreased by the suppressors of plasmalemma H(+)-ATPase activity, than that of WT control. The plasmalemma H(+)-ATPase activity in the germinating seeds of hrs1-1 was substantially lower than that exhibited by WT control, and fusicoccin, an activator of this pump, corrected the transient germination delay of hrs1-1. Together, our data suggest that HRS1 may be needed for suppressing ABA signaling in germinating embryo axis, which promotes the timely germination of Arabidopsis seeds probably by facilitating the proper function of plasmalemma H(+)-ATPase and the efficient elongation of LH and TZ cells.

High glucose mediates endothelial-to-chondrocyte transition in human aortic endothelial cells

Abstract: Vascular calcification is one of the common complications in diabetes mellitus. Many studies have shown that high glucose (HG) caused cardiovascular calcification, but its underlying mechanism is not fully understood. Recently, medial calcification has been most commonly described in the vessels of patients with diabetes. Chondrocytes were involved in the medial calcification. Recent studies have shown that the conversion into mesenchymal stem cells (MSCs) via the endothelial-to-mesenchymal transition (EndMT) could be triggered in chondrocytes. Our previous research has indicated that HG induced EndMT in human aortic endothelial cells (HAECs). Therefore, we addressed the question of whether HG-induced EndMT could be transitioned into MSCs and differentiated into chondrocytes. HAECs were divided into three groups: a normal glucose (NG) group, HG group (30 mmol/L), and mannitol (5.5 mmol/L NG + 24.5 mmol/L) group. Pathological changes were investigated using fluorescence microscopy and electron microscopy. Immunofluorescence staining was performed to detect the co-expression of endothelial markers, such as CD31, and fibroblast markers, such as fibroblast-specific protein 1 (FSP-1). The expression of FSP-1 was detected by real time-PCR and western blots. Endothelial-derived MSCs were grown in MSC medium for one week. The expression of the MSCs markers STRO-1, CD44, CD10 and the chondrocyte marker SOX9 was detected by immunofluorescence staining and western blots. Chondrocyte expression was detected by alcian blue staining. Calcium deposits were analyzed by alizarin red staining. The incubation of HAECs exposed to HG resulted in a fibroblast-like phenotype. Double staining of the HAECs indicated a co-localization of CD31 and FSP-1. The expression of FSP-1 was significantly increased in the HG group, and the cells undergoing EndMT also expressed STRO-1, CD44 and SOX9 compared with the controls (P < 0.05). Additionally, alcian blue staining in the HG group was positive compared to the NG group. Consistent with the evaluation of SOX9 expression, calcium deposits analyzed by alizarin red staining were also enhanced by the HG treatment. Specifically, we showed that HG-induced EndMT is accompanied by the activation of the canonical Snail pathway. Our study demonstrated that HG could induce endothelial cells transdifferentiation into chondrocyte-like cells via the EndMT, which is mediated in part by the activation of the Snail signaling pathway.

Nitrogen-doped In2O3 nanocrystals constituting hierarchical structures with enhanced gas-sensing properties

Abstract: Doping indium oxide with nitrogen species is a strategy to extend its photoresponse to the visible region and to modify its band structure, enabling the material to have potential applications in photocatalysis, optoelectronics, and sensors. In this paper, we report on a simple solvothermal synthesis method for producing nitrogen-doped indium oxide nanocrystals that are composed of hierarchical structures. The samples were characterized with XRD, Raman spectroscopy, SEM, HRTEM, FTIR, XPS, UV-vis, and photoluminescence techniques, and further tested in the role of an ethanol gas sensing material. The optical properties and the gas-sensing performance of indium oxide can be tuned by controlling the nitrogen doping. Also, the nitrogen species, resulting from the nitrogen doping, function like a surface modifier to enhance the sensitivity of the sensors that were made from the nitrogen-doped indium oxides on their exposure to ethanol gas.

The issues of prestack reverse time migration and solutions with Graphic Processing Unit implementation

Abstract: Prestack reverse time migration (RTM) is a very useful tool for seismic imaging but has mainly three bottlenecks: highly intensive computation cost, low-frequency band imaging noise and massive memory demand. Traditionally, PC-clusters with thousands of computation nodes are used to perform RTM but it is too expensive for small companies and oilfields. In this article, we use Graphic Processing Unit (GPU) architecture, which is cheaper and faster to implement RTM and we obtain an order of magnitude higher speedup ratio to solve the problem of intensive computation cost. Aiming at the massive memory demand, we adopt the pseudo random boundary condition that sacrifices the computation cost but reduces the memory demand. For rugged topography RTM, it is difficult to deal with the rugged free boundary condition with the finite difference method. We employ a simplified boundary condition that avoids the abundant logical judgment to make the GPU implementation possible and does not induce any sacrifice on efficiency. Besides, we have also done some tests on multi-GPU implementation for wide azimuth geometries using the latest GPU cards and drivers. Finally, we discuss the challenges of anisotropy RTM and GPU solutions. All the jobs stated above are based on GPU and the synthetic data examples will show the efficiency of the algorithm and solutions.

Ferroelectricity and superparamagnetism in Sr/Ti nonstoichiometric SrTiO3

Abstract: The effect of Sr/Ti nonstoichiometry on the ferroelectricity and magnetism in polycrystalline SrTiO3 is investigated by the dielectric, ferroelectric, Raman, and magnetic characterizations. It revealed that the nonstoichiometric SrTiO3 exhibits both ferroelectric polarization and superparamagnetism, which increase with the degree of nonstoichiometry. It is argued that the antisite-like defects with net local dipoles and magnetic moments contribute to the ferroelectricity and superparamagnetism, confirmed by the first-principles calculations.

Ammonium sulfate regulation of morphology of Nd:Y2O3 precursor via urea precipitation method and its effect on the sintering properties of Nd:Y2O3 nanopowders

Abstract: Ammonium sulfate has been widely used as a control agent in the preparation of yttrium-aluminium-garnet (YAG) transparent ceramics, however, research of its application in the preparation in transparent ceramic yttria has not been intensively studied. Neodymium–doped yttria (Nd:Y2O3) nanopowders with controlled morphology and size were synthesized via a urea precipitation method using ammonium sulfate as the additive. The effect of ammonium sulfate was intensively studied throughout the preparation process. Morphology of precursors was found to be evidently affected by the [(NH4)2SO4]/[Nd:Y2O3] ratio (measured by weight). Uniform spheres of Nd:Y2O3 precursor were obtained without the addition of ammonium sulfate. With increasing amounts of ammonium sulfate added, the scale of the Nd:Y2O3 precursors diminished which results in the aggregation of the Nd:Y2O3 precursor. Aggregates of coral like particles after precipitation and uniform well dispersed particles after calcinations were obtained as the dosage of ammonium sulfate reached 20 wt%. It was considered to be the optimum state for the preparation of highly sinterable Nd:Y2O3 nanopowders. Ammonium sulfate was proved to be a regulator that could mediate the nucleation and growth of the precursor as well as its decomposition behaviour. Results of this paper can contribute to the controllable synthesis of transparent ceramic yttria.

Highly Enantioselective Michael Addition of 2-Oxindole- 3-carboxylate Esters to Nitroolefins Promoted by Cinchona Alkaloid-Thiourea-Brønsted Acid Cocatalysts

Abstract: A highly efficient organocatalyzed Michael addition of 2-oxindole-3-carboxylate esters to nitroolefins using a Cinchona alkaloid-thiourea and an achiral Bronsted acid as cooperative organocatalysts is reproted that affords significantly improved enantioselectivity and diastereoselectivity. It also provides an efficient approach to the synthesis of spirooxindole derivatives with high enantioselectivity.