Xiujin Li

Porcine reproductive and respiratory syndrome virus activates inflammasomes of porcine alveolar macrophages via its small envelope protein E

Porcine reproductive and respiratory syndrome virus (PRRSV) infection results in extensive tissue inflammation and damage, which are believed to be responsible for increased susceptibility to secondary infection and even for death. However, its pathogenic mechanisms are not fully understood. To explore the mechanism underlying the PRRSV-induced tissue inflammation and damage, we investigated whether PRRSV activates porcine alveolar macrophage (PAM) inflammasomes which mediate por-IL-1β maturation/release and subsequently induce tissue inflammation and injury. Our results showed that PRRSV and its small envelope protein E significantly increased IL-1β release from LPS-primed PAMs; however, only PRRSV not protein E significantly increased IL-1β release from no-LPS-primed PAMs, which indicates PRRSV can activate inflammasomes of PAMs by its encoded protein E. These results provide a molecular basis for the pathogenic mechanism of PRRSV on inducing extensive tissue inflammation and damage, and suggest that the inflammasome may provide a potential therapeutic target for PRRS prevention and treatment.

Ni–Al diffusion barrier layer for integrating ferroelectric capacitors on Si

We report on the use of amorphous Ni–Al film (a-Ni–Al) as conductive diffusion barrier layer to integrate La0.5Sr0.5CoO3∕PbZr0.4Ti0.6O3∕La0.5Sr0.5CoO3 capacitors on silicon. Cross-sectional observation by transmission electron microscope reveals clean and sharp interfaces without any discernible interdiffusion/reaction in the sample. The physical properties of the capacitors are vertically characterized as the parameters of memory elements. Excellent ferroelectric properties, e.g., large remnant polarization of ∼22μC∕cm2, small coercive voltage of ∼1.15V, being fatigue-free, good retention characteristic, imply that amorphous Ni–Al is an ideal candidate for diffusion barrier for the high-density ferroelectric random access memories integrated with silicon transistor technology.

Atomic ordering kinetics of FePt thin films: Nucleation and growth of L10 ordered domains

To lower the L10 ordering temperature of FePt thin films, a detailed understanding of the nucleation and growth processes of L10 ordered domains is of particular importance. In the present study, a nucleation activation energy En=(0.5−0.6)±0.1 eV and a growth activation energy Eg=0.9±0.1 eV for the L10 ordered domains in the FePt thin films are determined by studying the individual annealing-temperature dependence of the nucleation and growth parameters of the L10 ordered domains. These data make a contribution to the understanding of the high L10 ordering temperature of FePt thin films for manufacturing magnetic recording media.

Codon optimization enhances secretory expression of Pseudomonas aeruginosa exotoxin A in E. coli

Pseudomonas aeruginosa exotoxin A (PEA) is a number of family of bacterial ADP-ribosylating toxins and possesses strong immunogenicity. The detoxified exotoxin A, as a potent vaccine adjuvant and vaccine carrier protein, has been extensively used in human and animal vaccinations. However, the expression level of PEA gene in Escherichia coli is relative low which is likely due to the presence of rare codon and high levels of GC content. In order to enhance PEA gene expression, we optimized PEA gene using E. coli preferred codons and expressed it in E. coli BL21 (DE3) by using pET-20b(+) secretory expression vector. Our results showed that codon optimization significantly reduced GC content and enhanced PEA gene expression (70% increase compared with that of the wild-type). Moreover, the codon-optimized PEA possessed biological activity and had the similar toxic effects on mouse L292 cells compared with the wild-type PEA gene. Codon optimization will not only improve PEA gene expression but also benefit further modification of PEA gene using nucleotide-mediated site-directed mutagenesis. A large number of purified PEA proteins will provide the necessary conditions for further PEA functional research and application.

Barrier performance of ultrathin Ni–Ti film for integrating ferroelectric capacitors on Si

Ultrathin amorphous Ni–Ti film is investigated as conductive diffusion barrier layer to integrate La0.5Sr0.5CoO3∕PbZr0.4Ti0.6O3∕La0.5Sr0.5CoO3 (LSCO/PZT/LSCO) capacitors on silicon. X-ray photoelectron spectroscopy results demonstrate that Ni in LSCO∕Ni–Ti∕Si heterostructure is not oxidized after 550°C annealing in oxygen. The structural properties of LSCO∕PZT∕LSCO∕Ni–Ti∕Si are characterized by x-ray diffraction and transmission electron microscopy. It is found that Ni–Ti film is still amorphous and that there are no discernible reactions at the interfaces of the sample. LSCO/PZT/LSCO capacitor, measured at 5V, possesses very good ferroelectric properties, such as low coercive field (∼1.28V), high remnant polarization (∼27.9μC∕cm2), and good fatigue-free characteristic, implying that ultrathin amorphous Ni–Ti film can be used as barrier layer for fabricating high-density ferroelectric random access memories.

Low-temperature synthesis of wurtzite ZnS single-crystal nanowire arrays

The synthesis of highly aligned and ordered wurtzite ZnS single-crystal nanowires at low temperatures is crucial for their applications in electronic and optoelectronic nanodevices. In the present study, wurtzite ZnS single-crystal nanowire arrays with a preferred growth along the [110] direction have been successfully prepared at a low temperature of T = 120 °C by employing electrochemical deposition techniques using the alumina template with 40 nm diameter pores. The microstructure of the ZnS nanowires was characterized by x-ray diffraction and transmission electron microscopy studies. A small deposition current is found to be favourable for the growth of wurtzite ZnS single-crystal nanowires and the cause has been discussed.

Soluble CD83 inhibits human monocyte differentiation into dendritic cells in vitro

Human CD83 is type I transmembrane glycoprotein, mainly expressed on mature dendritic cells (DCs), so it was first described as a molecular marker for mature DC. However, increasing evidence has demonstrated that CD83 is also an immunomodulatory molecule either its membrane-bound CD83 (mCD83) or soluble CD83 (sCD83) released from DCs. Intriguingly, the mCD83 possesses stimulatory effects on immune response, on the contrary, the sCD83 has inhibitory effects. Whether the sCD83 has the inhibitory effects on human monocyte differentiation into DCs is unknown. To this end, we prepared the recombinant human sCD83 in HEK293T cells and treated human monocytes being differentiated into DCs in vitro with the sCD83, and evaluate sCD83 inhibitory effects on immune response by analyzing the surface marker pattern of the cells. The results showed that the sCD83, especially glycosylated sCD83 could bind the monocytes and significantly inhibited the depression of CD14 expressions (P<0.01) and reduced CD1a, CD80, CD86 and MHC II expressions (P<0.01 or P<0.05) during the differentiation, indicating that the sCD83 can inhibit monocyte differentiation into DCs, and suggesting that a negative feedback regulation may exist in monocyte differentiation into DCs based on sCD83 released from the mature DCs.

Nucleation and growth processes of α-Fe nanocrystals in amorphous NdFeBCoDy: In situ x-ray diffraction studies

For a detailed understanding of formation processes of nanocrystals in an amorphous matrix, the study of crystal nucleation and growth processes is of basic interest. In the present study, these processes of α-Fe nanocrystals in amorphous NdFeCoDyB have been studied separately by employing in situ high-temperature x-ray diffraction measurements. A small growth activation energy Eg=(1.8±0.2)eV was determined from the isothermal time dependence of the grain size of α-Fe crystals. By these data together with the nucleation activation energy En=(3.0±0.1)eV, a coarse grain size for the α-Fe phase in the α-Fe∕Nd2Fe14B nanocomposites developed from amorphous NdFeBCoDy can be understood.

Molecular mechanism for the effects of E. coli heat-labile enterotoxin on mouse embryo survival.

Heat-labile enterotoxin (LT) can cause animal enteritis and diarrhea. However, the possible association of LT with embryo survival in pregnant animals and the mechanisms involved remain unknown. To investigate the effects of LT on embryo survival, we treated mouse early embryos in vitro and pregnant mice in vivo with recombinant LT. LT significantly decreased mouse embryo survival, and induced IFN-γ, IL-2 and IL-1β production in the serum and placental tissue. LT also triggered IL-1β release from LPS-primed microphages, suggesting LT can activate inflammasomes. To determine the pathway involved in LT-induced inflammasome activation, small interfering RNAs were used to knockdown NLRP3 and ASC, the key components of NLRP3 inflammasome pathway. Ablation of NLRP3 and ASC abolished LT-induced IL-1β release, confirming the involvement of NLRP3 inflammasome. By comparing two subunits of LT, only LTA but not LTB subunit was identified to activate the NLRP3 inflammasome.

Soluble Form of Canine Transferrin Receptor Inhibits Canine Parvovirus Infection In Vitro and In Vivo

Canine parvovirus (CPV) disease is an acute, highly infectious disease threatening the dog-raising industry. So far there are no effective therapeutic strategies to control this disease. Although the canine transferrin receptor (TfR) was identified as a receptor for CPV infection, whether extracellular domain of TfR (called soluble TfR (sTfR)) possesses anti-CPV activities remains elusive. Here, we used the recombinant sTfR prepared from HEK293T cells with codon-optimized gene structure to investigate its anti-CPV activity both in vitro and in vivo. Our results indicated that codon optimization could significantly improve sTfR expression in HEK293T cells. The prepared recombinant sTfR possessed a binding activity to both CPV and CPV VP2 capsid proteins and significantly inhibited CPV infection of cultured feline F81 cells and decreased the mortality of CPV-infected dogs, which indicates that the sTfR has the anti-CPV activity both in vitro and in vivo.