Ultrastructural aspects of phytoglycogen from cryo-TEM and quasi-elastic light scattering data

International audienc

Small-angle neutron scattering from diblock copolymer poly(styrene-d8)-b-poly(γ-benzyl L-glutamate) solutions: Rod-coil to coil-coil transition

The elastic properties of rod-coil diblock copolymer poly(styrene-d8)-b-poly(γ-benzyl L-glutamate) (PSd-b-PBLG) rod-coil diblock copolymer solutions were investigated using small-angle neutron scattering (SANS). PBLG is known to undergo a transition from a rodlike α-helical secondary structure to a random coil conformation under specific solvent conditions: the PBLG is (i) rodlike in dioxane and (ii) random coil in dioxane/trifluoroacetic acid (80/20). For the PSd-b-PBLG diblock copolymer, this conformational transition results in a topological change from a rod-coil to a coil-coil type structure. SANS results indeed show the presence of the expected scattering peaks-copolymer signature-for both conformational topologies. The position and the height of these scattering peaks are found in good agreement with a recent theoretical model that describes the conformational change in rod-coil diblock copolymer solutions. Circular dichroism experiments confirmed the change in secondary structure in the peptide block that accompanies the topological transition observed by SANS

Shear-induced orientation phenomena in suspensions of cellulose microcrystals, revealed by small angle X-ray scattering

International audienc

Coastal environments shape chemical and microbial properties of forest litters in the Circum-Mediterranean region

This study explores how chemical and microbial properties of litters can be affected by coastal environments across the Mediterranean basin. A litterbag experiment includingPinus halepensisMill. andPistacia lentiscusL., collected from both inland and coastal areas, was set up in France, Greece and Algeria. Control litterbags were left in their sampling sites and a transfer of litterbags from inland to coastal areas was performed to test whether the effect of the specific constraints of coastal environments varies according to the country and the litter type. After 10 months, litter chemical composition (CP/MAS(13)C-NMR) and microbial activities (cellulase activity, basal respiration, catabolic diversity using Biolog) and community structure (TRFLP) were analysed. Coastal conditions led to various responses: (i) litter aromaticity differed in the coastal zones depending on the country (high in the Greek coastal area, low in the Algerian coastal zone), (ii) fewer functionally diversified microbial communities were found in the Greek coastal area compared to the French and Algerian coasts, (iii) genetic diversity and richness were strongly impacted after transfer to the coastal zone whatever the country. The type of litter shaped microbial communities: (i) at a local scale (i.e., in either coastal or inland areas) catabolic profiles and cellulase activities varied with the plant species, (ii) at a regional scale, the effect of coastal conditions differed with the plant species (basal respiration, Shannon-Weaver index, catabolic diversity H ', cellulases and catabolic profiles). Thus, litter microbial properties differed in coastal environments across the Mediterranean basin and plant litter type plays a major role in microbial properties at a large spatial scale. Highlights The environmental drivers of litter microbial sensitivity to water potential stress were investigated Litterbag transfers from inland to coastal areas were performed in the Mediterranean. Soil and land system units conform to long-tail or heavy tail distributions. Microbial diversity of inland litters decreased when exposed to coastal conditions Litter plant species shape microbial functioning even at wide spatial scales. Coastal areas and plant litter drive microbial responses to water potential stress

Self-Assembly of Oligosaccharide- b -PMMA Block Copolymer Systems: Glyco-Nanoparticles and Their Degradation under UV Exposure

International audienc