The Geminiviridae is an extensive family of plant viruses responsible for economically devastating diseases in crops worldwide. Geminiviruses package circular, single-stranded DNA (ssDNA) genomes. The characteristic twinned or "geminate" particles, which consist of two joined, incomplete T = 1 icosahedra, are unique among viruses. We have determined the first structure of a geminivirus particle, the Nigerian strain of Maize streak virus (MSV-N), using cryo-electron microscopy and three-dimensional image reconstruction methods. The particle, of dimensions 220 x 380 A, has an overall 52-point-group symmetry, in which each half particle "head" consists of the coat protein (CP) arranged with quasi-icosahedral symmetry. We have modeled the MSV-N CP as an eight-stranded, antiparallel beta-barrel motif (a structural motif common to all known ssDNA viruses) with an N-terminal alpha-helix. This has produced a model of the geminate particle in which 110 copies of the CP nicely fit into the reconstructed density map. The reconstructed density map and MSV-N pseudo-atomic model demonstrate that the geminate particle has a stable, defined structure.

Serologic and molecular evidence indicates that peste des petits ruminants virus (PPRV) infection has emerged in goats and sheep in the Ngari region of southwestern Tibet, People’s Republic of China. Phylogenetic analysis confirms that the PPRV strain from Tibet is classified as lineage 4 and is closely related to viruses currently circulating in neighboring countries of southern Asia.

This work seeks to optimize the twin‐screw compounding of polymer‐clay nanocomposites (PCNs). Proportional amounts (3:1) of maleic anhydride functionalized polypropylene compatibilizer (PP‐g‐MA) and organically modified montmorillonite clay at clay loadings of 1, 3, and 5 wt% were melt‐blended with a polypropylene (PP) homopolymer using a Leistritz Micro 27 twin‐screw extruder. Three melt‐blending approaches were pursued: (1) a masterbatch of PP‐g‐MA and organoclay were blended in one pass followed by dilution with the PP resin in a second pass; (2) all three components were processed in a single pass; and (3) uncompatibilized PP and organoclay were processed twice. Both corotation and counterrotation operation were utilized to investigate the effect of screw rotation mode and sequence on organoclay exfoliation and dispersion. X‐ray diffraction was employed to characterize basal spacing; however, since rheology is known to be highly sensitive to mesoscale organoclay structure, it is an ideal tool to examine the relationship between the various processing methods and exfoliation and dispersion. A holistic analysis of rheological data demonstrates the efficacy of the masterbatch approach, particularly when compatibilizer and organoclay are blended in counterrotating mode followed by dilution with matrix polymer in corotating mode. POLYM. ENG. SCI., 47:898–911, 2007. © 2007 Society of Plastics Engineers

Yellow fever (YF) is a viral disease endemic to the tropical regions of Africa and South America. An outbreak of YF has been occurring in Angola, since the beginning of 2016. In March 2016, a 32-year-old Chinese man who returned from Angola was hospitalized and diagnosed with the first case of imported YF in China. Clinical observations, blood viral RNA detection, serological testing and treatments for the patient were performed daily. The virus was isolated in Vero cells, and the complete viral genome was sequenced and analyzed using the next-generation genomic sequencing platform. The patient presented with hemorrhagic fever, jaundice and oliguria at day 3 after onset, which rapidly progressed to multisystem organ failure with extremely elevated liver, pancreatic and myocardial enzymes. The patient died despite the intensive supportive treatments that were performed. A liver biopsy showed severe and multilobular necrosis. Viral RNA was detectable throughout the clinical course of the disease. Whole-genomic sequence analysis revealed that the virus belongs to the Angola71 genotype. Although the virus has been circulating in Angola for 45 years, only 14 amino-acid substitutions and no amino-acid changes were observed in the membrane and envelope proteins compared with the virus collected in 1971. The presence of this imported YF case in China indicated that with the increase in business travel among countries, YF outbreaks in Africa can lead to the international spread of the disease. The production and use of YF vaccines is, therefore, an urgent issue.