Thermally Switchable Nanogate Based on Polymer Phase Transition

Mimicking and extending the gating properties of biological pores is of paramount interest for the fabrication of membranes that could be used in filtration or drug processing. Here, we build a selective and switchable nanopore for macromolecular cargo transport. Our approach exploits polymer graftings within artificial nanopores to control the translocation of biomolecules. To measure transport at the scale of individual biomolecules, we use fluorescence microscopy with a zero-mode waveguide set up. We show that grafting polymers that exhibit a lower critical solution temperature creates a toggle switch between an open and closed state of the nanopore depending on the temperature. We demonstrate tight control over the transport of DNA and viral capsids with a sharp transition (∼1 °C) and present a simple physical model that predicts key features of this transition. Our approach provides the potential for controllable and responsive nanopores in a range of applications

Study of the interactions of organic sulfides with active species in the cationic polymerization of 1,3-pentadiene

Different alkyl sulfides (dimethylsulfide, ditertiobutylsulfide and diphenylsulfide) were investigated in the polymerization of 1,3-pentadiene initiated by aluminum trichloride in polar solvent in order to control the polymerization and to study the interaction between the electron donor and the active species. Thus, it was found that dimethylsulfide totally inhibited the polymerization, while thanks to its steric hindrance the polymerization occurred in the presence of ditertiobutylsulfide. However, for this electron donor, a transfer activity was evidenced at room temperature and at 0degreesC, which contributes to prevent the control of the polymerization. Diphenylsulfide stabilizes a little the active centers with nearly no transfer reaction. However in the studied experimental conditions, the stabilization was not sufficient to obtain a living polymerization

Determinants of survival and dispersal along the range expansion of a biological invasion

International audienceA mechanistic understanding of how individual- and environment-level factors influence species demography and range dynamics is paramount to our ability to accurately project future biodiversity. Such knowledge is particularly crucial for invasive species, which expansion may have far-reaching consequences for native ecosystems. Here, we experimentally examine how survival and dispersal respond to multiple individual- and environment-level factors in the red swamp crayfish Procambarus clarkii, one of the most invasive species worldwide, along an invasion gradient. Crayfish survival probability was (i) positively dependent on body size-dependent at high (but not low) crayfish density and on temperature, and was (ii) negatively dependent on body condition and crayfish density. Dispersal probability was positively dependent on body-size, body condition and temperature. In contrast, survival and dispersal probabilities were similar among range-core and range-edge crayfish, suggesting no evolution of the range-expansion potential along the invasion gradient. Our study highlights in an invasive aquatic species that alterations of body-size structure, population density and temperature, as driven by global anthropogenic changes, may lead to demographic reorganizations that will ultimately shift demographic ranges and determine future biodiversity patterns. From a management perspective, our results show that range expansion in P. clarkii will be promoted by future climate warming, and should be most efficiently hindered by selectively removing large-bodied individuals

An alternative approach to create N -substituted cyclic dipeptides

International audienceN-Modified peptide backbones are promising peptidomimetics which offer several advantages in terms of improved biological activity and stability. They further allow the development of novel functional materials. However, the synthesis of N-substituted peptides is very challenging with the existing methods, particularly the synthesis of peptides with larger N-substituents. In this work, we are introducing a new method to create N-polyether substituted cyclic dipeptides via anionic ring-opening polymerization (AROP). Four different cyclic dipeptides with different hydrophobic functional groups were selected to create N-substituted cyclic dipeptides. Backbone amides –NH– were deprotonated with phosphazene bases to form nucleophilic initiators. Furthermore, the effect of different phosphazene bases (tBuP4 and tBuP2) and of the addition of a Lewis acid (i-Bu3Al) was studied in detail towards creating N-polyether-cyclic dipeptides bearing either hydrophobic poly(butylene oxide) chains, or hydrophilic linear polyglycidol chains, thanks to the polymerization of 1,2-epoxybutane and the polymerization followed by the deprotection of t-butyl glycidyl ether monomers, respectively. Moreover, we have demonstrated the possibility of avoiding the isomerization of cyclic dipeptides during the synthesis of N-substituted analogues depending on the synthetic approach

Synthesis of tetraarm star block copolymer based on polytetrahydrofuran and poly(2-methyl-2-oxazoline) for gene delivery applications

International audienceNew star shaped block copolymers were synthesized according to a core first strategy, with a hydrophobic polytetrahydrofuran (PTHF) central block and a poly(2-methyl-2-oxazoline) (PMeOx) external block. First, the cationic polymerization of THF was initiated from a tetrafunctional triflate ester synthesized in situ. The chain ends were functionalized by quenching the polymerization with an excess of MeOx, that allowed for the MeOx polymerization under microwave in a subsequent step. Demonstration of the expected structures was carried out at each step of the polymerization. The controlled molar mass of the star copolymers was kept below 5000 g mol À1 in order to mimick the structure of the efficient poloxamines for gene transfer applications. Formulations containing various concentrations of star block copolymers were intramuscularly injected in mice. Efficient gene transfer was measured at formulations with very low concentration of copolymer compared to reference standard containing Lutrol Ò

β-Cyclodextrin-Based Star Amphiphilic Copolymers: Synthesis, Characterization, and Evaluation as Artificial Channels

International audience14‐arm amphiphilic star copolymers are synthesized according to different strategies. First, the anionic ring polymerization of 1,2‐butylene oxide (BO) initiated by per(2‐O‐methyl‐3,6‐di‐O‐(3‐hydroxypropyl))‐β‐CD (β‐CD’OH14) and catalyzed by t‐BuP4 in DMF is investigated. Analyses by NMR and SEC show the well‐defined structure of the star β‐CD’‐PBO14. To obtain a 14‐arm poly(butylene oxide‐b‐ethylene oxide) star, a Huisgen cycloaddition between an α‐methoxy‐ω‐azidopoly(ethylene oxide) and the β‐CD’‐PBO14,whose end‐chains are beforehand alkyne‐functionalized, is performed. In parallel, 14‐arm star copolymers composed of butylene oxide‐b‐glycidol arms are successfully synthesized by the anionic polymerization of ethoxyethylglycidyl ether (EEGE) initiated by β‐CD’‐PBO14 with t‐BuP4. The deprotection of EEGE units is then performed to provide the polyglycidol blocks. These amphiphilic star polymers are evaluated as artificial channels in lipid bilayers. The effect of changing a PEO block by a polyglycidol block on the insertion properties of these artificial channels is discussed