Manipulating hyperbolic transient plasmons in a layered semiconductor.

Anisotropic materials with oppositely signed dielectric tensors support hyperbolic polaritons, displaying enhanced electromagnetic localization and directional energy flow. However, the most reported hyperbolic phonon polaritons are difficult to apply for active electro-optical modulations and optoelectronic devices. Here, we report a dynamic topological plasmonic dispersion transition in black phosphorus via photo-induced carrier injection, i.

Tunable heterostructural prism for planar polaritonic switch.

The study of phonon polaritons in van der Waals materials at the nanoscale has gained significant attention in recent years due to its potential applications in nanophotonics. The unique properties of these materials, such as their ability to support sub-diffraction imaging, sensing, and hyperlenses, have made them a promising avenue for the development of new techniques in the field. Despite these advancements, there still exists a challenge in achieving dynamically reversible manipulation of phonon polaritons in these materials due to their insulating properties.

Ultralow-Loss Phonon Polaritons in the Isotope-Enriched α-MoO.

α-MoO, a natural van der Waals (vdWs) material, has received wide attention in nano-optics for supporting highly confined anisotropic phonon polaritons (PhPs) from the mid-infrared to the terahertz region, which opens a new route for manipulating light at the nanoscale. However, its optical loss hinders light manipulation with high efficiency. This work demonstrates that the isotope-enriched Mo element enables ultralow-loss PhPs in the α-MoO.

Humanizing the yeast origin recognition complex.

The Origin Recognition Complex (ORC) is an evolutionarily conserved six-subunit protein complex that binds specific sites at many locations to coordinately replicate the entire eukaryote genome. Though highly conserved in structure, ORC's selectivity for replication origins has diverged tremendously between yeasts and humans to adapt to vastly different life cycles. In this work, we demonstrate that the selectivity determinant of ORC for DNA binding lies in a 19-amino acid insertion helix in the Orc4 subunit, which is present in yeast but absent in human.

Structure of the origin recognition complex bound to DNA replication origin.

The six-subunit origin recognition complex (ORC) binds to DNA to mark the site for the initiation of replication in eukaryotes. Here we report a 3 Å cryo-electron microscopy structure of the Saccharomyces cerevisiae ORC bound to a 72-base-pair origin DNA sequence that contains the ARS consensus sequence (ACS) and the B1 element. The ORC encircles DNA through extensive interactions with both phosphate backbone and bases, and bends DNA at the ACS and B1 sites.

Independent and interactive effects of ambient temperature and absolute humidity on the risks of avian influenza A(H7N9) infection in China.

The emergence of avian influenza A(H7N9) virus poses a pandemic threat to human beings. It was proposed that meteorological factors might be important environmental factors favoring the occurrence of H7N9 infection, but evidence is still inadequate. In this study, we aimed to investigate the independent and interactive effects of ambient temperature (TM) and absolute humidity (AH) on H7N9 infection risks in China.

Chikungunya virus nsP4 RNA-dependent RNA polymerase core domain displays detergent-sensitive primer extension and terminal adenylyltransferase activities.

Chikungunya virus (CHIKV) is an important arboviral infectious agent in tropical and subtropical regions, often causing persistent and debilitating disease. The viral enzyme non-structural protein 4 (nsP4), as RNA-dependent RNA polymerase (RdRP), catalyzes the formation of negative-sense, genomic and subgenomic viral RNAs. Here we report a truncated nsP4 construct that is soluble, stable and purified recombinantly from Escherichia coli.

The C-terminal 18 Amino Acid Region of Dengue Virus NS5 Regulates its Subcellular Localization and Contains a Conserved Arginine Residue Essential for Infectious Virus Production.

Dengue virus NS5 is the most highly conserved amongst the viral non-structural proteins and is responsible for capping, methylation and replication of the flavivirus RNA genome. Interactions of NS5 with host proteins also modulate host immune responses. Although replication occurs in the cytoplasm, an unusual characteristic of DENV2 NS5 is that it localizes to the nucleus during infection with no clear role in replication or pathogenesis.

Molecular basis for specific viral RNA recognition and 2'-O-ribose methylation by the dengue virus nonstructural protein 5 (NS5).

Dengue virus (DENV) causes several hundred million human infections and more than 20,000 deaths annually. Neither an efficacious vaccine conferring immunity against all four circulating serotypes nor specific drugs are currently available to treat this emerging global disease. Capping of the DENV RNA genome is an essential structural modification that protects the RNA from degradation by 5' exoribonucleases, ensures efficient expression of viral proteins, and allows escape from the host innate immune response.

Structural insight and flexible features of NS5 proteins from all four serotypes of Dengue virus in solution.

Infection by the four serotypes of Dengue virus (DENV-1 to DENV-4) causes an important arthropod-borne viral disease in humans. The multifunctional DENV nonstructural protein 5 (NS5) is essential for capping and replication of the viral RNA and harbours a methyltransferase (MTase) domain and an RNA-dependent RNA polymerase (RdRp) domain. In this study, insights into the overall structure and flexibility of the entire NS5 of all four Dengue virus serotypes in solution are presented for the first time.

Flexibility of NS5 Methyltransferase-Polymerase Linker Region Is Essential for Dengue Virus Replication.

We examined the function of the conserved Val/Ile residue within the dengue virus NS5 interdomain linker (residues 263 to 272) by site-directed mutagenesis. Gly substitution or Gly/Pro insertion after the conserved residue increased the linker flexibility and created slightly attenuated viruses. In contrast, Pro substitution abolished virus replication by imposing rigidity in the linker and restricting NS5's conformational plasticity.

A crystal structure of the Dengue virus NS5 protein reveals a novel inter-domain interface essential for protein flexibility and virus replication.

Flavivirus RNA replication occurs within a replication complex (RC) that assembles on ER membranes and comprises both non-structural (NS) viral proteins and host cofactors. As the largest protein component within the flavivirus RC, NS5 plays key enzymatic roles through its N-terminal methyltransferase (MTase) and C-terminal RNA-dependent-RNA polymerase (RdRp) domains, and constitutes a major target for antivirals. We determined a crystal structure of the full-length NS5 protein from Dengue virus serotype 3 (DENV3) at a resolution of 2.

The C-terminal 50 amino acid residues of dengue NS3 protein are important for NS3-NS5 interaction and viral replication.

Dengue virus multifunctional proteins NS3 protease/helicase and NS5 methyltransferase/RNA-dependent RNA polymerase form part of the viral replication complex and are involved in viral RNA genome synthesis, methylation of the 5'-cap of viral genome, and polyprotein processing among other activities. Previous studies have shown that NS5 residue Lys-330 is required for interaction between NS3 and NS5. Here, we show by competitive NS3-NS5 interaction ELISA that the NS3 peptide spanning residues 566-585 disrupts NS3-NS5 interaction but not the null-peptide bearing the N570A mutation.

Identification and molecular characterization of human antibody fragments specific for dengue NS5 protein.

The multifunctional dengue nonstructural (NS) protein 5 from the four serotypes of dengue virus (DENV1-4) is essential for viral replication and harbors a methyl transferase (MTase) and a RNA-dependent RNA-polymerase domain (RdRp). There are limited comparative studies of NS5 from the four DENV serotypes and this is further hampered by a lack of cross-reactive NS5 antibodies. In this study, recombinant NS5 proteins were expressed, purified, enzymatically characterized, and used strategically as bait in biopanning experiments with a naïve human Fab phage-display library to identify serotype specific or cross-reactive Fab fragments.

Detection of border disease virus (BDV) in goat herds suffering diarrhea in eastern China.

Background: Border disease virus (BDV) is an important pathogen in sheep and goat production. Neither epidemiological investigation nor any reports of BDV infection was available in China. During Jan to Apr, 2012, several herd goats in Anhui and Jiangsu provinces in eastern China suffered unremitting diarrhea, with morbidity and mortality of about 28-37% and 10-15%, respectively.

The effect of salt on oligocation-induced chromatin condensation.

Condensation of model chromatin in the form of fully saturated 12-mer nucleosome arrays, induced by addition of cationic ligands (ε-oligolysines with charge varied from +4 to +11), was studied in a range of KCl concentrations (10-500mM) using light scattering and precipitation assay titrations. The dependence of EC(50) (ligand concentration at the midpoint of the array condensation) on C(KCl) displays two regimes, a salt-independent at low C(KCl) and a salt-dependent at higher salt concentrations. In the salt-dependent regime EC(50) rises sharply with increase of C(KCl).