Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes.

The confinement of air-protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer-precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface-modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT-confined iron nanoparticles coated with a polyisoprene air barrier.

Comparative mapping in the Fagaceae and beyond with EST-SSRs.

Background: Genetic markers and linkage mapping are basic prerequisites for comparative genetic analyses, QTL detection and map-based cloning. A large number of mapping populations have been developed for oak, but few gene-based markers are available for constructing integrated genetic linkage maps and comparing gene order and QTL location across related species.

Results: We developed a set of 573 expressed sequence tag-derived simple sequence repeats (EST-SSRs) and located 397 markers (EST-SSRs and genomic SSRs) on the 12 oak chromosomes (2n = 2x = 24) on the basis of Mendelian segregation patterns in 5 full-sib mapping pedigrees of two species: Quercus robur (pedunculate oak) and Quercus petraea (sessile oak).

Theoretical and experimental studies on the carbon-nanotube surface oxidation by nitric acid: interplay between functionalization and vacancy enlargement.

The nitric acid oxidation of multiwalled carbon nanotubes leading to surface carboxylic groups has been investigated both experimentally and theoretically. The experimental results show that such a reaction involves the initial rapid formation of carbonyl groups, which are then transformed into phenol or carboxylic groups. At room temperature, this reaction takes place on the most reactive carbon atoms.

A fast and cost-effective approach to develop and map EST-SSR markers: oak as a case study.

Background: Expressed Sequence Tags (ESTs) are a source of simple sequence repeats (SSRs) that can be used to develop molecular markers for genetic studies. The availability of ESTs for Quercus robur and Quercus petraea provided a unique opportunity to develop microsatellite markers to accelerate research aimed at studying adaptation of these long-lived species to their environment. As a first step toward the construction of a SSR-based linkage map of oak for quantitative trait locus (QTL) mapping, we describe the mining and survey of EST-SSRs as well as a fast and cost-effective approach (bin mapping) to assign these markers to an approximate map position.

Metabolic control through ornithine and uracil of epithelial cell invasion by Shigella flexneri.

This paper shows that compounds in defined growth media strongly influence the expression of the effectors of virulence in the human invasive pathogen Shigella flexneri. Ornithine in conjunction with uracil reduces the haemolytic ability of wild-type cultures more than 20-fold and the expression of the type III secretion system more than 8-fold, as monitored by an mxiC : : lacZ transcriptional reporter. mxiC gene expression is further decreased by the presence of methionine or branched-chain amino acids (15-fold or 25-fold at least, respectively).

New atropisomeric N-N ligands for CO/vinyl arene copolymerization reaction.

New atropisomeric bidentate bipyridine-based ligands (3,3'-(ethylenedioxy)-2,2'-bipyridine 4; 3,3'-(propylenedioxy)-2,2'-bipyridine 4; 3,3'-(butylenedioxy)-2,2'-bipyridine 5) containing a bridge between the 3,3' positions of the aromatic rings have been prepared. Together with the previously reported analogous ligands ((R)-3,3'-(1-methylethylenedioxy)-2,2'-bipyridine) 1and ((S,S)-3,3'-(1,2-dimethylethylenedioxy)-2,2'-bipyridine) 2, they were used to synthesize the corresponding bis-chelated dicationic complexes [Pd(N-N)2][PF6]2. Crystal structures and comparison of the data obtained by X-ray analysis on four of these complexes is reported.

Palladium catalyzed Suzuki C-C couplings in an ionic liquid: nanoparticles responsible for the catalytic activity.

A new family of functionalized ligands derived from norborn-5-ene-2,3-dicarboxylic anhydride has been used in Suzuki C-C cross-couplings between aryl boronic acids and aryl bromide derivatives in [BMI][PF(6)] (BMI=1-n-butyl-3-methyl-imidazolium), using palladium acetate as catalytic precursor. High conversions and yields are obtained when amine ligands containing hydroxy groups are involved. TEM analyses after catalysis show the formation of small nanoparticles, in contrast to the agglomerates observed when nanoparticles are intentionally preformed, with a consequent decrease in the catalytic activity in the latter case.

Dissection of the barley 2L1.0 region carrying the 'Laevigatum' quantitative resistance gene to leaf rust using near-isogenic lines (NIL) and subNIL.

Partial resistance to leaf rust (Puccinia hordei G. H. Otth) in barley is a quantitative resistance that is not based on hypersensitivity.

Long-lived palladium catalysts for CO/vinyl arene polyketones synthesis: a solution to deactivation problems.

A series of cationic palladium complexes of general formula [Pd(Me)(MeCN)(N-N)][PF(6)] (N-N = (phen) 1 a, 4,7-dichloro-1,10-phenanthroline (4,7-Cl(2)-phen) 2 a, 4,7-diphenyl-1,10-phenanthroline (4,7-Ph(2)-phen) 3 a, 4-methyl-1,10-phenanthroline (4-Me-phen) 4 a, 4,7-dimethyl-1,10-phenanthroline (4,7-Me(2)-phen) 5 a, 5,5,6,6-tetrafluoro-5,6-dihydro-1,10-phenanthroline (F(4)-phen) 6 a, containing different substituted phenanthroline ligands, have been prepared from the corresponding neutral chloro derivatives [Pd(Me)(Cl)(N-N)], (1 b-6 b). The X-ray crystal structure of [Pd(Cl)(2)(4,7-Cl(2)-phen)] (2 b') was determined. DFT calculations show that the electron density on the metal is tuned by the substituents on the ligands.

Mono- and dinuclear bioxazoline-palladium complexes for the stereocontrolled synthesis of CO/styrene polyketones.

The coordination chemistry of the chiral bioxazoline ligand (4S,4'S)-2,2'-bis(4-isopropyl-4,5-dihydrooxazole) to Pd(II) provides evidence that the ligand bonding can occur either through chelation of one Pd(II) ion leading to a mononuclear species with the expected cis geometry, or by double bridging of two Pd(II) ions giving a dinuclear complex with trans geometry. The species in solution are identified by 1H NMR spectroscopy. Both the mononuclear and the dinuclear complexes promote the CO/styrene copolymerization, yielding the corresponding polyketone with a fully or a predominantly isotactic microstructure, depending on the reaction medium.

Transfer RNA modifications that alter +1 frameshifting in general fail to affect -1 frameshifting.

Using mutants (tgt, mnmA(asuE, trmU), mnmE(trmE), miaA, miaB, miaE, truA(hisT), truB) of either Escherichia coli or Salmonella enterica serovar Typhimurium and the trm5 mutant of Saccharomyces cerevisiae, we have analyzed the influence by the modified nucleosides Q34, mnm(5)s(2)U34, ms(2)io(6)A37, Psi39, Psi55, m(1)G37, and yW37 on -1 frameshifts errors at various heptameric sequences, at which at least one codon is decoded by tRNAs having these modified nucleosides. The frequency of -1 frameshifting was the same in congenic strains only differing in the allelic state of the various tRNA modification genes. In fact, in one case (deficiency of mnm(5)s(2)U34), we observed a reduced ability of the undermodified tRNA to make a -1 frameshift error.

Putrescine or a combination of methionine and arginine restores virulence gene expression in a tRNA modification-deficient mutant of Shigella flexneri: a possible role in adaptation of virulence.

The wild-type strain YSH6000 of Shigella flexneri growing in minimal medium contains the modified nucleoside epoxy-Q (oQ) in a subset of tRNAs. This nucleoside is lacking in tRNA from a tgt mutant of this bacterium. When these bacteria are growing in minimal medium, the expression of virulence genes is 10-fold lower in the tgt mutant than in the wild type, although only a twofold reduction in the expression of these virulence factors is observed in broth.

Three modifications in the D and T arms of tRNA influence translation in Escherichia coli and expression of virulence genes in Shigella flexneri.

The modified nucleosides 2'-O-methylguanosine, present at position 18 (Gm18), 5-methyluridine, present at position 54 (m(5)U54), and pseudouridine, present at position 55 (Psi55), are located in the D and T arms of tRNAs and are close in space in the three-dimensional (3D) structure of this molecule in the bacterium Escherichia coli. The formation of these modified nucleosides is catalyzed by the products of genes trmH (Gm18), trmA (m(5)U54), and truB (Psi55). The combination of trmH, trmA, and truB mutations resulting in lack of these three modifications reduced the growth rate, especially at high temperature.