Simultaneous B'V'R' Monitoring of BL Lacertae Object S5~0716+714 and Detection of Inter-Band Time Delay

We present the results of our optical monitoring of the BL Lac object S5 0716+714 on seven nights in 2006 December. The monitoring was carried out simultaneously at three optical wavelengths with a novel photometric system. The object did not show large-amplitude internight variations during this period. Intranight variations were observed on four nights and probably on one more. Strong bluer-when-brighter chromatism was detected on both intranight and internight timescales. The intranight variation amplitude decreases in the wavelength sequence of B', R', and V'. Cross correlation analyses revealed that the variability at the $B'$ and $V'$ bands lead that at the $R'$ band by about 30 minutes on one night.Comment: 31 pages, 12 figures, accepted by the Astronomical Journa

DDX21, a Host Restriction Factor of FMDV IRES-Dependent Translation and Replication

In cells, the contributions of DEAD-box helicases (DDXs), without which cellular life is impossible, are of utmost importance. The extremely diverse roles of the nucleolar helicase DDX21, ranging from fundamental cellular processes such as cell growth, ribosome biogenesis, protein translation, protein–protein interaction, mediating and sensing transcription, and gene regulation to viral manipulation, drew our attention. We designed this project to study virus–host interactions and viral pathogenesis. A pulldown assay was used to investigate the association between foot-and-mouth disease virus (FMDV) and DDX21. Further insight into the DDX21–FMDV interaction was obtained through dual-luciferase, knockdown, overexpression, qPCR, and confocal microscopy assays. Our results highlight the antagonistic feature of DDX21 against FMDV, as it progressively inhibited FMDV internal ribosome entry site (IRES) -dependent translation through association with FMDV IRES domains 2, 3, and 4. To subvert this host helicase antagonism, FMDV degraded DDX21 through its non-structural proteins 2B, 2C, and 3C protease (3Cpro). Our results suggest that DDX21 is degraded during 2B and 2C overexpression and FMDV infection through the caspase pathway; however, DDX21 is degraded through the lysosomal pathway during 3Cpro overexpression. Further investigation showed that DDX21 enhanced interferon-beta and interleukin-8 production to restrict viral replication. Together, our results demonstrate that DDX21 is a novel FMDV IRES trans-acting factor, which negatively regulates FMDV IRES-dependent translation and replication

One-Pot Synthesis of Dendritic Gold Nanostructures in Aqueous Solutions of Quaternary Ammonium Cationic Surfactants: Effects of the Head Group and Hydrocarbon Chain Length

Hierarchical, three-fold symmetrical dendritic gold was prepared in an aqueous solution of the quaternary ammonium cationic surfactant dodecyltrimethylammonium bromide (DTAB). Similar surfactants with different head groups and hydrocarbon chain lengths were also used for comparison. Two-fold and one-fold symmetrical dendritic gold nanostructures were obtained in N-dodecyl-N-methylpyrrolidinium bromide (C₁₂-MPB) and dodecyltriethylammonium bromide (DTEAB) aqueous solutions, respectively. Longer hydrocarbon chain lengths were unfavorable for the formation of dendritic nanostructures. The interaction energies between the individual surfactants and Au (111) plane were calculated using molecular dynamics simulations. Based on a series of contrast experiments and molecular dynamics simulations, the possible growth mechanism and fabrication process of the dendritic structures were proposed. The DTAB-capped, three-fold gold dendrites exhibited good surface-enhanced Raman scattering (SERS) sensitivity toward rhodamine 6G (R6G), indicating their potential for use in SERS-based detections and analysis. This work provides a simple and effective strategy for fabricating dendritic gold nanostructures in aqueous solutions