Electron diffraction study on the polysaccharide from Watsonia pyramidata corm sacs

International audienc

An electron diffraction study of paramylon storage granules from Euglena gracillis.

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An electron diffraction study of single crystals of amylose complexed with n-butanol

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Single crystals of amylose with a low degree of polymerization

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The capsid architecture of channel catfish virus, an evolutionarily distant herpesvirus, is largely conserved in the absence of discernible sequence homology with herpes simplex virus

Although herpesviruses have a wide host range and their genomes vary substantially in size, the nucleocapsid appears to be a conservative element of viral design. The capsid shell is icosahedrally symmetric (T = 16), and 125 nm in diameter and 15nm thick in the case of herpes simplex virus 1 (HSV-1). Channel catfish virus (CCV) has the gross morphology of a herpesvirus, although no relationship to other herpesviruses is evident from the sequences of its proteins. To examine CCV capsid architecture more closely, we have determined its structure by cryoelectron microscopy and three-dimensional image reconstruction. The CCV capsid is smaller than that of HSV-1, but its 12% smaller genome is packed to essentially the same average density; its icosahedral facets are flatter, and its shell is about 20% thinner, consistent with the smaller size of its major capsid protein. Otherwise, their major features are remarkably similar: CCV has the same triangulation number; its hexons and pentons also have chimney-like protrusions with an axial channel through each capsomer; and there are "triplexes" on the outer surface at the sites of local threefold symmetry. The basic herpesvirus capsid architecture is, therefore, remarkably well conserved in CCV and implies a utilitarian basis to this design. The protein composition of CCV mirrors that of HSV-1, except for the absence of the 12-kDa protein, VP26, which is dispensable for assembly in the HSV-1 system and, apparently, wholly dispensable for CCV

Molecular characterization of a partitivirus from Ophiostoma himal-ulmi

The complete nucleotide sequences of two double-stranded (ds) RNA molecules, S1 (1,744 bp) and S2 (1,567 bp), isolated from an isolate HP62 of the Himalayan Dutch elm disease fungus, Ophiostoma himal-ulmi, were determined. RNA S1 had the potential to encode a protein, P1, of 539 amino acids (62.7 kDa), which contained sequence motifs characteristic of RNA-dependent RNA polymerases (RdRps). A database search showed that P1 was closely related to RdRps of members of the genus Partitivirus in the family Partitiviridae. RNA S2 had the potential to encode a protein, P2, of 430 amino acids (46.3 kDa), which was related to capsid proteins of members of the genus Partitivirus. Virus particles isolated from isolate HP62 were shown to be isometric with a diameter of 30 nm, and to contain dsRNAs S1 and S2 and a single capsid protein of 46 kDa. N-terminal sequencing of tryptic peptides derived from the capsid protein proved unequivocally that it is encoded by RNA S2 and corresponds to protein P2. It is concluded that O. himal-ulmi isolate HP62 contains a new member of the genus Partitivirus, which is designated Ophiostoma partitivirus 1. A phylogenetic tree of RdRps of members of the family Partitiviridae showed that there are least two RdRp lineages of viruses currently classified in the genus Partitivirus. One of these lineages contained viruses with fungal hosts and viruses with plant hosts, raising the possibility of horizontal transmission of partitiviruses between plants and fungi. The partitivirus RdRp and capsid proteins appear to have evolved in parallel with the capsid proteins evolving much faster than the RdRps.Peer reviewe

Visualization of dendrimer molecules by transmission electron microscopy (TEM): staining methods and cryo-TEM of vitrified solutions

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Quenching of CdSe quantum dot emission, a new approach for biosensing

The emission of CdSe quantum dots linked to the 5'-end of a DNA sequence is efficiently quenched by hybridisation with a complementary DNA strand with a gold nanoparticle attached at the 3'-end; contact of the quantum dot and gold nanoparticle occurs