Valessa Barbier

New block‐copolymer thermoassociating matrices for DNA sequencing: Effect of molecular structure on rheology and resolution

A new family of matrices for DNA sequencing by capillary electrophoresis is presented. These matrices combine easy injection with high sieving performances, due to thermal switching between a low and a high viscosity state through a modest increase in temperature (˜20°C). They are constructed from a hydrophilic polymer backbone with grafted lower critical solution temperature (LCST) side chains. The comb‐like LCST copolymers are characterized in terms of size of the polymer backbone, the size of LCST side chains and the grafting densities. The dependance of rheological behavior and electrophoretic performance of these copolymers is correlated with their microstructure. Without complete optimization, a resolution of order 0.5, corresponding to a very reasonable limit for read length with current base calling softwares, could be achieved for segments around 800 bases differing by 1 base in less than one hour in a commercial ABI 310 apparatus.

Advanced polymers for DNA separation

Recent research to improve matrices for DNA separation has resulted in the development of advanced polymers for use in capillary electrophoresis and, more generally, for electrophoresis in microchannels. To date, the most commonly used matrix is linear polyacrylamide (LPA). Unfortunately, the high-molecular weight LPA solutions required for achieving good resolution lead to very viscous solutions. Moreover, the coating ability of LPA is very poor. For these reasons, many research groups have developed low-viscosity matrices, which make microchannel filling easier, and self-coating matrices, which are able to reduce efficiently the electro-osmotic flow and the interaction of DNA with the capillary wall. To this purpose, thermo-adjustable viscosity polymers represent a very clever and interesting class of matrices.

Comb-like copolymers as self-coating, low-viscosity and high-resolution matrices for DNA sequencing

Comb‐like copolymers with a polyacrylamide backbone and poly(N,N‐dimethylacrylamide) grafts were prepared, as a way to combine the superior sieving properties of polyacrylamide with the self‐coating properties of polydimethylacrylamide. These matrices function well in the absence of a capillary coating, and achieve separation performances for single‐stranded DNA that are comparable to those of state‐of‐the‐art long‐chain linear polyacrylamide. Structural parameters such as the grafting density and the polymer molecular mass were varied, and good performance appears to be achieved with a relatively large range of parameters. Surprisingly, excellent separation is achieved even with matrices that have a viscosity as low as 200 mPa/s. A discussion of the physics underlying this behavior is provided.

Metal-Free Activation in the Anionic Ring-Opening Polymerization of Cyclopropane Derivatives

The successful activation observed when using Bu(t) P(4) phosphazene base and thiophenol or bisthiols for the anionic ring opening polymerization (ROP) of di-n-propyl cyclopropane-1,1-dicarboxylate is described. Well-defined monofunctional or difunctional polymers with a very narrow molecular weight distribution were obtained through a living process. Quantitative end-capping of the propagating malonate carbanion was accessible by using either an electrophilic reagent such as allyl bromide or a strong acid such as HCl. Kinetics studies demonstrated a much higher reactivity compared to the conventional route using alkali metal thiophenolates.

Self-assembly of amphiphilic liquid crystal polymers obtained from a cyclopropane-1,1-dicarboxylate bearing a cholesteryl mesogen.

We study the self-assembly of a new family of amphiphilic liquid crystal (LC) copolymers synthesized by the anionic ring-opening polymerization of a new cholesterol-based LC monomer, 4-(cholesteryl)butyl ethyl cyclopropane-1,1-dicarboxylate. Using the t-BuP(4) phosphazene base and thiophenol or a poly(ethylene glycol) (PEG) functionalized with thiol group to generate in situ the initiator during the polymerization, LC homopolymer and amphiphilic copolymers with narrow molecular weight distributions were obtained. The self-assemblies of the LC monomer, homopolymer, and block copolymers in bulk and in solution were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and transmission electron microscopy (TEM). All polymers exhibit in bulk an interdigitated smectic A (SmA(d)) phase with a lamellar period of 4.6 nm. The amphiphilic copolymers self-organize in solution into vesicles with wavy membrane and nanoribbons with twisted and folded structures, depending on concentration and size of LC hydrophobic block. These new morphologies will help the comprehension of the fascinating organization of thermotropic mesophase in lyotropic structures.

A polymeric membrane permeabilizer displaying densely packed arrays of crown ether lateral substituents

We report the design, synthesis and evaluation of a novel macromolecular membrane permeabilizer displaying geminally substituted crown-ethers (18-crown-6) on every third carbon alongside the backbone. The polymer has a rather high affinity with potassium as well as permeabilization properties towards K+, Na+ and Ca2+, including single-channel behavior.

New glycopolymers as multivalent systems for lectin recognition

New types of glycopolymers have been designed and evaluated as multivalent systems for lectin recognition. They were prepared by living Anionic Ring-Opening Polymerization (AROP) of disubstituted cyclopropane-1,1-dicarboxylates and thiol–ene post-modification. Fully modified oligomers with single or geminal sugar substituents located on every third carbon alongside the macromolecular scaffold were obtained under mild conditions. The resulting glycopolymers have shown efficient binding potency towards concanavalin A.