Nature's lessons in design: nanomachines to scaffold, remodel and shape membrane compartments.

Compartmentalisation of cellular processes is fundamental to regulation of metabolism in Eukaryotic organisms and is primarily provided by membrane-bound organelles. These organelles are dynamic structures whose membrane barriers are continually shaped, remodelled and scaffolded by a rich variety of highly sophisticated protein complexes. Towards the goal of bottom-up assembly of compartmentalised protocells in synthetic biology, we believe it will be important to harness and reconstitute the membrane shaping and sculpting characteristics of natural cells. We review different in vitro membrane models and how biophysical investigations of minimal systems combined with appropriate theoretical modelling have been used to gain new insights into the intricate mechanisms of these membrane nanomachines, paying particular attention to proteins involved in membrane fusion, fission and cytoskeletal scaffolding processes. We argue that minimal machineries need to be developed and optimised for employment in artificial protocell systems rather than the complex environs of a living organism. Thus, well-characterised minimal components might be predictably combined into functional, compartmentalised protocellular materials that can be engineered for wide-ranging applications

Layered Double Hydroxyde platelets exfoliation into a water-based polyester

International audienceNitrate layered double hydroxide (LDH) phase Zn2Al(OH)6(NO3)*2H2O is successfully exfoliated in the presence of polyester under mild conditions using water as essential solvent and at room temperature under air. From small angle X-ray scattering spectroscopy a total exfoliation is found to be achieved using up to 10 wt % LDH, while intercalated polymer nanocomposite structures largely extended up to 14 nm are observed for loading ranging from 10 to 20 wt %. The process is found to be explained by the diffusion of the polymer chain into the interlayer host structure. Starting from an initial value of 0.89 nm, ≈3, 7, 10, 14, and 20 nm transient interleaved nanostructures are formed without any carbonate uptake. The collective gap distance is certainly due to a defined number of polymer chains diffusing into the LDH interstices. Similarly, starting from an aqueous polyester solution highly concentrated in LDH nitrate phase up to 50% w.w, successive dilutions yield platelet exfoliation, thus rendering a smooth chemistry process attractive for potential application

Percolation network of organo-modified layered double hydroxide platelets into polystyrene showing enhanced rheological and dielectric behavior

International audienceA hybrid organic inorganic layered double hydroxide incorporating 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) is characterized by means of XRD, FTIR, and XPS. The in situ polymerization is scrutinized by 13C CPMAS as well as by a set of XRD experiments with varying temperature. It is found that the in situ polymerization is complete at 200 °C, and the hybrid framework sustains temperatures as high as 350 °C. Direct incorporation of poly(AMPS) is reported and the resulting hybrid LDH phases studied. Subsequently, all generated hybrid platelets are used as organo-modified 2D-type filler dispersed into polystyrene (PS). An immiscible PS composite structure with salient gel-like viscoelastic properties is obtained after bulk polymerization. In the low-frequency region, the typical Newtonian flow behaviour of PS is found to change progressively against filler loading into a shear-thinning behaviour evidenced by a pseudo-plateau in the elastic and loss modulus curves and associated with a shift of the glass transition temperature of PS to higher temperature. It is interpreted by hybrid LDH platelet domains presenting a large interface with the polymer, thus having the effect of restricting the plastic deformation by obstructing polymer chain motion. Such dispersed hybrid LDH tactoids forming a three-dimensional percolated network are indirectly evidenced by the enhancement of the dielectric properties illustrated by an increase in bulk dc conductivity of about one order at room temperature and in the dissipation factor. The study shows that hybrid LDH assembly is of relevance in topical applications regarding mechanical reinforcement as well as electrostatic energy dissipation. © 2010 The Royal Society of Chemistry