Magnetic Field Induced Charge Instabilities in Weakly Coupled Superlattices

Using a time dependent selfconsistent model for vertical sequential tunneling,we study the appearance of charge instabilities that lead to the formation of electric field domains in a weakly coupled doped superlattice in the presence of high magnetic fields parallel to the transport direction. The interplay between the high non linearity of the system --coming from the Coulomb interaction-- and the inter-Landau-level scattering at the domain walls (regions of charge accumulation inside the superlattice) gives rise to new unstable negative differential conductance regions and extra stable branches in the sawtooth-like I-V curves.Comment: 5 pages, 4 postscript figure

An IL-27-Driven Transcriptional Network Identifies Regulators of IL-10 Expression across T Helper Cell Subsets.

Interleukin-27 (IL-27) is an immunoregulatory cytokine that suppresses inflammation through multiple mechanisms, including induction of IL-10, but the transcriptional network mediating its diverse functions remains unclear. Combining temporal RNA profiling with computational algorithms, we predict 79 transcription factors induced by IL-27 in T cells. We validate 11 known and discover 5 positive (Cebpb, Fosl2, Tbx21, Hlx, and Atf3) and 2 negative (Irf9 and Irf8) Il10 regulators, generating an experimentally refined regulatory network for Il10. We report two central regulators, Prdm1 and Maf, that cooperatively drive the expression of signature genes induced by IL-27 in type 1 regulatory T cells, mediate IL-10 expression in all T helper cells, and determine the regulatory phenotype of colonic Foxp3 <sup>+</sup> regulatory T cells. Prdm1/Maf double-knockout mice develop spontaneous colitis, phenocopying ll10-deficient mice. Our work provides insights into IL-27-driven transcriptional networks and identifies two shared Il10 regulators that orchestrate immunoregulatory programs across T helper cell subsets

Genome organization in the caliciviridae

Caliciviruses cause a wide spectrum of important diseases. These viruses have a positive-sense single-stranded RNA genome; recently, the complete genome sequences of several caliciviruses have been determined. This review outlines the genome organization and phylogenetic relationships of the animal and candidate human caliciviruses

Stable cloning of the amino terminus of the 60k outer membrane protein of Chlamydia trachomatis serovar L1

A mixed twenty-five base oligonucleotide probe was synthesized to the amino terminus of the 60 kDa cysteine-rich outer membrane protein of Chlamydia trachomatis serovar F. This probe hybridized to a single band in Southern blots of C. trachomatis serovar L1 DNA. However, repeated attempts at screening plasmid-based genomic libraries failed to yield positive signals. As an alternative approach, bacteriophage M13 was used as the primary cloning vector. With this vector two identical stable recombinants were isolated carrying a 2.2 kb Pst1 insert that hybridized to the oligonucleotide probe. Attempts to re-clone this fragment in plasmid-based vectors yielded very small unstable colonies. DNA encoding the amino terminus of the 60 kDa outer membrane protein was further localised to a 274 bp Sau3A fragment which was sub-cloned in both orientations in m13. DNA sequence analysis of this fragment from C. trachomatis serovar L1 demonstrated a perfect 15/15 amino acid match to the amino terminus of the 60 kDa outer membrane protein from C. trachomatis serovar F. On the basis of these results we suggest bacteriophage M13 as a general cloning vector to avoid the toxic effects of the amino termini of foreign outer membrane proteins in Escherichia coli

Viral gastroenteritis: the human caliciviruses

The caliciviruses are a major cause of viral gastroenteritis but the lack of diagnostic procedures has resulted in their role being under-rated. Norwalk-like viruses are detected by negative stain electron microscopy and their appearance results in their being called small round structured viruses. Spread is by food and contamination of the environment by vomitus. There are many genetic variants and only small numbers of virus particles are shed during infection. Sapporo-like viruses have a 3-fold axis of symmetry and are usually associated with paediatric gastroenteritis. Cell culture systems are lacking. There is no long-lived immunity following infection. Hand washing and protective clothing are essential during outbreaks

Molecular cloning and sequence analysis of a developmentally regulated cysteine-rich outer membrane protein from Chlamydia trachomatis.

Two overlapping genomic fragments have been cloned from Chlamydia trachomatis serovar L1 DNA. Sequence determination of 2530 bp has revealed two open reading frames coding for 'cysteine-rich' (Cr) proteins. One of these proteins was confirmed, by analysis of the inferred amino acid sequence, as the 60-kDa Cr outer membrane protein associated with differentiation of reticulate bodies (RBs) into elementary bodies (EBs). The other smaller 15-kDa protein contained a high percentage of methionine and cysteine and may correspond to a reported smaller and co-ordinately synthesised Cr outer-membrane protein also associated with RB to EB differentiation. Sequencing showed three potential stem-loop structures within the 5', 3' and intergenic regions of the cloned fragment. Southern-blot analysis revealed that the cloned fragment is conserved in ten serovars of C. trachomatis and that a strongly cross-hybridising fragment is also present in Chlamydia psittaci

Polyprotein processing in Southampton virus: identification of 3C-like protease cleavage sites by in vitro mutagenesis

A genomic clone of the small, round-structured virus Southampton virus (SV) was constructed from a set of overlapping PCR amplicons. Sequence analysis confirmed the absence of mutations and accurate ligation of the PCR products. The SV cDNA was cloned into a vector for in vitro production of RNA and subsequent translation by rabbit reticulocyte lysate. Two polypeptides corresponding to the N-terminal and C-terminal regions of the viral polyprotein were expressed in Escherichia coli and used to produce murine antisera for detection of translation products. Three major translation products of 113, 48, and 41 kDa were identified in a coupled transcription-translation system. The large 113-kDa protein reacted with antisera raised against the C-terminal region of the polyprotein and represents a precursor of the viral RNA polymerase. The 48-kDa protein detected in vitro reacted specifically with antisera raised against the polyprotein N terminus, showing that translation was initiated in SV at the three tandem in-frame AUG codons at the 5' end of the genome. A series of nested 3' deletions of the large open reading frame encoding the viral polyprotein was used to define the translation initiation site and genomic location of the viral protease. The results are consistent with a model in which translation of the viral genome is initiated at one of the three in-frame AUG codons starting at nucleotide position 5 and in which active viral protease is produced following translation of a region located between NheI (nucleotide 3052) and SphI (nucleotide 4056), resulting in rapid cleavage of a large precursor protein. Abolition of the viral 3C-like protease activity by site-directed mutagenesis of the putative active-site cysteine (Cys-1238) resulted in production of a large protein of approximately 200 kDa which reacted with both N-terminal and C-terminal antisera. Two potential polyprotein cleavage sites containing the preferred picornaviral QG recognition site were identified on either side of the putative 2C-like helicase region of the polyprotein. Proteolysis at these positions would give rise to products with relative molecular masses identical to those of the products detected in the rabbit reticulocyte system. Site-directed mutagenesis was used to introduce a single base change which resulted in the substitution of glutamine residues with proline residues at amino acids 399 and 762. These mutations completely abolished cleavage of the polyprotein at these positions and gave rise to alternative products with molecular masses which matched the predicted sizes for a single cleavage at either Q-399 or Q-762. These data indicate that the small, round-structured virus Southampton virus produces a 3C-like protease which has two primary cleavage sites at positions 399 and 762. Proteolytic cleavage at these positions releases the putative viral 2C-like helicase

A conserved sequence motif at the 5' terminus of the Southampton virus genome is characteristic of the Caliciviridae

We have determined the 5'terminal cDNA sequence for the genome of Southampton virus, a recently characterized, human, small round-structured virus (SRSV). Genomic RNA was extracted directly from a stool sample and amplified by RT-PCR by homopolymer tailing of the 3' terminus of the cDNA. The additional sequence increases the overall length of the Southampton virus genome by 12 nucleotides, resulting in a significant change to the genome organization by extending the first large open reading frame (ORF) by 51 amino acids. The 5'terminal bases pGpT and the presence of conserved genome and putative subgenomic RNA terminal motifs are now prominent features shared between the human SRSV Southampton virus and the animal caliciviruses rabbit hemorrhagic disease virus and feline calicivirus