Transfection with fluorinated lipoplexes based on fluorinated analogues of DOTMA, DMRIE and DPPES

AbstractFluorinated double-chain (poly)cationic lipids (one or both of these chains being ended by a highly fluorinated tail) which are close analogues of DOTMA, DMRIE or DPPES were designed as synthetic vectors for gene delivery. For N/P ratios (N=number of amine functions of the lipid; P=number of DNA phosphates) from 0.8 to 5, these fluorinated cationic lipids condensed DNA, with or without the use of DOPE, to form fluorinated lipoplexes. No specific cell toxicity was evidenced for these new fluorinated lipoplexes. The efficiency of some of the fluorinated lipoplexes to transfect lung epithelial A549 cells was comparable to that of the first generation of fluorinated lipoplexes made from fluorinated analogues of DOGS (Transfectam) [Bioconjug. Chem. 12 (2001) 114]. These results, combined with the higher in vivo transfection potential found for fluorinated lipoplexes than for conventional lipoplexes or PEI polyplexes [J. Gene Med. 3 (2001) 109], confirm that fluorinated lipoplexes are very promising gene transfer systems

P2CS:Updates of the prokaryotic two-component systems database

International audienceThe P2CS database (http://www.p2cs.org/) is a comprehensive resource for the analysis of Prokaryotic Two-Component Systems (TCSs). TCSs are comprised of a receptor histidine kinase (HK) and a partner response regulator (RR) and control important prokaryotic behaviors. The latest incarnation of P2CS includes 164 651 TCS proteins, from 2758 sequenced prokaryotic genomes. Several important new features have been added to P2CS since it was last described. Users can search P2CS via BLAST, adding hits to their cart, and ho-mologous proteins can be aligned using MUSCLE and viewed using Jalview within P2CS. P2CS also provides phylogenetic trees based on the conserved signaling domains of the RRs and HKs from entire genomes. HK and RR trees are annotated with gene organization and domain architecture, providing insights into the evolutionary origin of the contemporary gene set. The majority of TCSs are encoded by adjacent HK and RR genes, however, 'orphan' unpaired TCS genes are also abundant and identifying their partner proteins is challenging. P2CS now provides paired HK and RR trees with proteins from the same genetic locus indicated. This allows the appraisal of evolutionary relationships across entire TCSs and in some cases the identification of candidate partners for orphan TCS proteins

Modulation of Metabolism and Switching to Biofilm Prevail over Exopolysaccharide Production in the Response of Rhizobium alamii to Cadmium

Heavy metals such as cadmium (Cd2+) affect microbial metabolic processes. Consequently, bacteria adapt by adjusting their cellular machinery. We have investigated the dose-dependent growth effects of Cd2+ on Rhizobium alamii, an exopolysaccharide (EPS)-producing bacterium that forms a biofilm on plant roots. Adsorption isotherms show that the EPS of R. alamii binds cadmium in competition with calcium. A metabonomics approach based on ion cyclotron resonance Fourier transform mass spectrometry has showed that cadmium alters mainly the bacterial metabolism in pathways implying sugars, purine, phosphate, calcium signalling and cell respiration. We determined the influence of EPS on the bacterium response to cadmium, using a mutant of R. alamii impaired in EPS production (MSΔGT). Cadmium dose-dependent effects on the bacterial growth were not significantly different between the R. alamii wild type (wt) and MSΔGT strains. Although cadmium did not modify the quantity of EPS isolated from R. alamii, it triggered the formation of biofilm vs planktonic cells, both by R. alamii wt and by MSΔGT. Thus, it appears that cadmium toxicity could be managed by switching to a biofilm way of life, rather than producing EPS. We conclude that modulations of the bacterial metabolism and switching to biofilms prevails in the adaptation of R. alamii to cadmium. These results are original with regard to the conventional role attributed to EPS in a biofilm matrix, and the bacterial response to cadmium

Evolutionary history expands the range of signaling interactions in hybrid multikinase networks

Two-component systems (TCSs) are ubiquitous signaling pathways, typically comprising a sensory histidine kinase (HK) and a response regulator, which communicate via intermolecular kinase-to-receiver domain phosphotransfer. Hybrid HKs constitute non-canonical TCS signaling pathways, with transmitter and receiver domains within a single protein communicating via intramolecular phosphotransfer. Here, we report how evolutionary relationships between hybrid HKs can be used as predictors of potential intermolecular and intramolecular interactions (‘phylogenetic promiscuity’). We used domain-swap genes chimeras to investigate the specificity of phosphotransfer within hybrid HKs of the GacS–GacA multikinase network of Pseudomonas brassicacearum. The receiver domain of GacS was replaced with those from nine donor hybrid HKs. Three chimeras with receivers from other hybrid HKs demonstrated correct functioning through complementation of a gacS mutant, which was dependent on strains having a functional gacA. Formation of functional chimeras was predictable on the basis of evolutionary heritage, and raises the possibility that HKs sharing a common ancestor with GacS might remain components of the contemporary GacS network. The results also demonstrate that understanding the evolutionary heritage of signaling domains in sophisticated networks allows their rational rewiring by simple domain transplantation, with implications for the creation of designer networks and inference of functional interactions

Synthese et evaluation d'amphiphiles F-alkyles analogues de phospholipides; preparation et etude physicochimique de liposomes et emulsions

SIGLEINIST T 76953 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Ecotoxicity of manufactured Al nanophases

International audienceWe examined the toxicity of two Al nanophases, viz. nano-boehmite and the Al13 tridecamer, a nano-sized Al polymer. Boehmite is a common Al oxyhydroxide; it is considered as non toxic. In a first approximation, nano-boehmite is also considered as harmless, by analogy with the larger sized counterpart.There are only isolated reports of the occurence of Al13 in natural environments. It is a hydrolysis product of Al3+ and is frequently used in water treatment processes, and may thus enter ecosystems using this route. As a matter of fact, typical Al concentration used in drinking water plants were also used here. The Al13 species is knwon to exhibit severe toxic effects towards crops.Nano-boehmite as well as Al13 exhibit toxic effects toward P. Brassicacearum and E. Coli. Oxidative stress is a likely mechanisms. Indeed, the E Coli sodAsodB double mutant showed increased sensitivity to Al stress compared to the wild strain. A remarkable point is theamplitude of the responses which differs greatly whether AlOOH or Al13 is present in the medium. With P. Brassicacearum, the toxic effects in terms of survival rate observed with nano-boehmite occur also in the presence of Al13 at concentrations lower by 2 orders of magnitude. With E. Coli, the same trend was observed. In this case, the increased sensitivity of the superoxide dismutase deficient strains was evident from the lowest tested concentrations (0.1mM).The evolution of the Al speciation occurred on a timescale incompatible with NMR analyses. Ferron based determinations showed however that the Al13 nanophase becomes undetectable in the growth medium within 90 minutes. Proton NMR based metabolomics suggest thatdistinct metabolic routes are affected by nano-boehmite and Al1

Ecotoxicity of manufactured Al nanophases

International audienceWe examined the toxicity of two Al nanophases, viz. nano-boehmite and the Al13 tridecamer, a nano-sized Al polymer. Boehmite is a common Al oxyhydroxide; it is considered as non toxic. In a first approximation, nano-boehmite is also considered as harmless, by analogy with the larger sized counterpart.There are only isolated reports of the occurence of Al13 in natural environments. It is a hydrolysis product of Al3+ and is frequently used in water treatment processes, and may thus enter ecosystems using this route. As a matter of fact, typical Al concentration used in drinking water plants were also used here. The Al13 species is knwon to exhibit severe toxic effects towards crops.Nano-boehmite as well as Al13 exhibit toxic effects toward P. Brassicacearum and E. Coli. Oxidative stress is a likely mechanisms. Indeed, the E Coli sodAsodB double mutant showed increased sensitivity to Al stress compared to the wild strain. A remarkable point is theamplitude of the responses which differs greatly whether AlOOH or Al13 is present in the medium. With P. Brassicacearum, the toxic effects in terms of survival rate observed with nano-boehmite occur also in the presence of Al13 at concentrations lower by 2 orders of magnitude. With E. Coli, the same trend was observed. In this case, the increased sensitivity of the superoxide dismutase deficient strains was evident from the lowest tested concentrations (0.1mM).The evolution of the Al speciation occurred on a timescale incompatible with NMR analyses. Ferron based determinations showed however that the Al13 nanophase becomes undetectable in the growth medium within 90 minutes. Proton NMR based metabolomics suggest thatdistinct metabolic routes are affected by nano-boehmite and Al1

Déplacement de bactéries en milieux poreux

* INRA Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9 Diffusion du document : INRA Centre d'Avignon, Documentation, Domaine St Paul, Site Agroparc, 84914 Avignon cedex 9National audienc

Destabilization of montmorillonite suspensions by Ca2+ and succinoglycan

International audienceAggregation of colloidal clay particles (Na-montmorillonite) by CaCl2 and anionic polysaccharide (succinoglycan) in turbulent conditions was investigated using time-resolved size measurements by laser diffraction on diluted (50 mg l(-1)) and stirred suspensions. Excess of Ca2+ ions promotes coagulation of the clay, reducing interparticle repulsions, and allows adsorption of succinoglycan, inducing bridging flocculation. Growth/breakage cycles, characteristic of the turbulent conditions, cause the macromolecules to be incorporated in the innermost of the flocs, where the morphological units are shown by confocal microscopy to be the micrometric Ca-clay particles. Such incorporation results in an increased floc tensile strength, depending on the amount of macromolecules adsorbed, with a maximum at polysaccharide concentrations of 2 wt.% with respect to clay mass