Supramolecular rods via halogen bonding-based self-assembly of fluorinated phosphazene nanopillars

A cyclotriphosphazene derivative bearing six 4-iodotetrafluorophenyl-substituted arms self-assembles with dipyridyl derivatives under the control of N?I halogen bonding to give rise to complexes where the starting modules are present in a 1:3 stoichiometric ratio, respectively. The directionality of the N?I halogen bonding translates the pillar-like arrangement adopted by the cyclotriphosphazene module into the rod-shaped supramolecular structure of the formed infinite chains. The invariance of N?I interactions translates the different size of the used dipyridyl modules into different pitches along the self-assembled rods. The obtained supramolecular architectures show a remarkable structural similarity confirming the reliability of halogen bonding in the design of complex supramolecular networks.     

Pseudomonas corrugata contains a conserved N-acyl homoserine lactone quorum sensing system; its role in tomato pathogenicity and tobacco hypersensitivity response

Pseudomonas corrugata is a phytopathogenic bacterium, causal agent of tomato pith necrosis, yet it is an ubiquitous bacterium that is part of the microbial community in the soil and in the rhizosphere of different plant species. Although it is a very heterogeneous species, all the strains tested were able to produce short chain acyl homoserine lactone (AHL) quorum sensing signal molecules. The main AHL produced was N-hexanoyl-L-homoserine lactone (C(6)-AHL). An AHL quorum sensing system, designated PcoI/PcoR, was identified and characterized. The role of the quorum sensing system in the expression of a variety of traits was evaluated. Inactivation of pcoI abolished the production of AHLs. The pcoR mutant, but not the pcoI mutant, was impaired in swarming, unable to cause a hypersensitivity response on tobacco and resulted in a reduced tomato pith necrosis phenotype. The pcoI mutant showed a reduced antimicrobial activity against various fungi and bacteria when assayed on King's B medium. These results demonstrate that the AHL quorum sensing in Ps. corrugata regulates traits that contribute to virulence, antimicrobial activity and fitness. This is the first report of genes of Ps. corrugata involved in the disease development and biological control activity.     

Bacteriophage P2: recombination in the superinfection preprophage state and under replication control by phage P4

Genetic crosses (mixed infection, lytic cycle) with bacteriophage P2 are known to give extremely low recombination frequencies, and these are unaffected by the recA status of the host bacterium. We now show the following: (1) the satellite bacteriophage P4, which interacts with P2 in a number of ways, but is quite different from it in terms of DNA replication and its control, is clearly dependent on the host recA+ function for recombination; (2) a chimeric phage (Lindqvist's P2/P4 Hy19), in which P2 replication early genes have been replaced by those of P4, recombines in a recA+-dependent manner; (3) immunity-sensitive P2 phages, in mixed infections of P2-immune bacteria, and hence blocked in their replication, recombine in a recA+-dependent manner; (4) an analysis of the distribution of exchanges based on a simple model confirms that in mixed infections of sensitive cells (where P2 is actively multiplying) recombinational exchanges tend to be statistically clustered in a segment of the chromosome containing the origin of replication, and also shows that, under conditions in which P2 DNA replication is blocked, the distribution of exchanges correlates well with the physical distances between markers on the P2 DNA.     

Reactivity of trans-[PtCl2(NCMe)2] with cycloaliphatic amines: An ESI and NMR study. X-ray structure of

The reactivity of the cyclic primary aliphatic amines cyclopropyl-, cyclopentyl- and cyclohexylamine with cis- and trans-[PtCl₂(NCMe)₂], under the same experimental conditions, is compared. Whereas cis-[PtCl₂(NCMe)₂] yields the neutral diamidine compounds, the reactions with trans-[PtCl₂(NCMe)₂] take place either with addition or substitution processes yielding the neutral diamidine complexes trans-[PtCl₂(Amidine)₂], the monocationic trans-[PtCl(Amine)(Amidine)₂]Cl and the dicationic trans-[Pt(Amine)₂(Amidine)₂]Cl₂ salts. An NMR and ESI study indicate that the main species formed is the monocationic trans-[PtCl(Amine)(Amidine)₂]Cl complex.The X-ray structure of is reported and its supramolecular arrangement is described.     

Proton-decoupled 15N and 31P solid-state NMR investigations of the Pf3 coat protein in oriented phospholipid bilayers

The coat proteins of filamentous phage are first synthesized as transmembrane proteins and then assembled onto the extruding viral particles. We investigated the transmembrane conformation of the Pseudomonas aeruginosa Pf3 phage coat protein using proton-decoupled 15N and 31P solid-state NMR spectroscopy. The protein was either biochemically purified and uniformly labelled with 15N or synthesized chemically and labelled at specific sites. The proteins were then reconstituted into oriented phospholipid bilayers and the resulting samples analysed. The data suggest a model in which the protein adopts a tilted helix with an angle of approximately 30 degrees and an N-terminal 'swinging arm' at the membrane surface.     

Synthesis and SAR of substituted tetrahydrocarbazole derivatives as new NPY-1 antagonists

The SAR of a new series of tetrahydrocarbazole derivatives is described: the appropriate decoration of this template led to the identification of a new class of NPY-1 antagonists showing good in vitro potency and a promising in vivo pharmacokinetic profile in rat.