Nano-building block based-hybrid organic–inorganic copolymers with self-healing properties

New dynamic materials, that can repair themselves after strong damage, have been designed by hybridization of polymers with structurally well-defined nanobuilding units. The controlled design of cross-linked poly(n-butyl acrylate) (pBuA) has been performed by introducing a very low amount of a specific tin oxo-cluster. Sacrificial domains with non-covalent interactions (i.e. ionic bonds) developed at the hybrid interface play a double role. Such interactions are strong enough to cross-link the polymer, which consequently exhibits rubber-like elasticity behavior and labile enough to enable, after severe mechanical damage, dynamic bond recombination leading to an efficient healing process at room temperature. In agreement with the nature of the reversible links at the hybrid interface, the healing process can speed up considerably with temperature. 1H and 119Sn PFG NMR has been used to evidence the dynamic nature of these peculiar cross-linking nodes

Tomato EF-Tsmt, a functional mitochondrial translation elongation factor from higher plants

Ethylene-induced ripening in tomato (Lycopersicon esculentum) resulted in the accumulation of a transcript designated LeEF-Tsmt that encodes a protein with significant homology to bacterial Ts translational elongation factor (EF-Ts). Transient expression in tobacco and sunflower protoplasts of full-length and truncated LeEF-Tsmt- GFP fusion constructs and confocal microscopy observations clearly demonstrated the targeting of LeEF-Tsmt to mitochondria and not to chloroplasts and the requirement for a signal peptide for the proper sorting of the protein. Escherichia coli recombinant LeEF-Tsmt co-eluted from Ni-NTA resins with a protein corresponding to the molecular weight of the elongation factor EF-Tu of E. coli, indicating an interaction with bacterial EF-Tu. Increasing the GDP concentration in the extraction buffer reduced the amount of EF-Tu in the purified LeEF-Tsmt fraction. The purified LeEF-Tsmt stimulated the poly(U)-directed polymerization of phenylalanine 10-fold in the presence of EF-Tu. Furthermore, LeEF-Tsmt was capable of catalysing the nucleotide exchange reaction with E. coli EF-Tu. Altogether, these data demonstrate that LeEF-Tsmt encodes a functional mitochondrial EF-Ts. LeEFTsmt represents the first mitochondrial elongation factor to be isolated and functionally characterized in higher plants

Batch fabrication of scanning microscopy probes for thermal and magnetic imaging using standard micromachining

We present a process for batch fabrication of a novel scanning microscopy probe for thermal and magnetic imaging using standard micromachining and conventional optical contact lithography. The probe features an AFM-type cantilever with a sharp pyramidal tip composed of four freestanding silicon nitride nanowires coated by conductive material. The nanowires form an electrical cross junction at the apex of the tip, addressable through the electrodes integrated on the cantilever. The cross junction on the tip apex can be utilized to produce heat and detect local temperature changes or to serve as a miniaturized Hall magnetometer enabling, in principle, thermal and magnetic imaging by scanning the probe tip over a surface. We have successfully fabricated a first probe prototype with a nanowire tip composed of 140 nm thick and 11 μ m long silicon nitride wires metallized by 6 nm titan and 30 nm gold layers. We have experimentally characterized electrical and thermal properties of the probe demonstrating its proper functioning. ©2010 IEEE

Microsatellite diversity and broad scale geographic structure in a model legume: building a set of nested core collection for studying naturally occurring variation in Medicago truncatula

BACKGROUND: Exploiting genetic diversity requires previous knowledge of the extent and structure of the variation occurring in a species. Such knowledge can in turn be used to build a core-collection, i.e. a subset of accessions that aim at representing the genetic diversity of this species with a minimum of repetitiveness. We investigate the patterns of genetic diversity and population structure in a collection of 346 inbred lines representing the breadth of naturally occurring diversity in the Legume plant model Medicago truncatula using 13 microsatellite loci distributed throughout the genome. RESULTS: We confirm the uniqueness of all these genotypes and reveal a large amount of genetic diversity and allelic variation within this autogamous species. Spatial genetic correlation was found only for individuals originating from the same population and between neighbouring populations. Using a model-based clustering algorithm, we identified four main genetic clusters in the set of individuals analyzed. This stratification matches broad geographic regions. We also identified a set of "admixed" individuals that do not fit with this population structure scheme. CONCLUSION: The stratification inferred is discussed considering potential historical events like expansion, refuge history and admixture between neighbouring groups. Information on the allelic richness and the inferred population structure are used to build a nested core-collection. The set of inbred lines and the core collections are publicly available and will help coordinating efforts for the study of naturally occurring variation in the growing Medicago truncatula community

Unconventional motional narrowing in the optical spectrum of a semiconductor quantum dot

Motional narrowing refers to the striking phenomenon where the resonance line of a system coupled to a reservoir becomes narrower when increasing the reservoir fluctuation. A textbook example is found in nuclear magnetic resonance, where the fluctuating local magnetic fields created by randomly oriented nuclear spins are averaged when the motion of the nuclei is thermally activated. The existence of a motional narrowing effect in the optical response of semiconductor quantum dots remains so far unexplored. This effect may be important in this instance since the decoherence dynamics is a central issue for the implementation of quantum information processing based on quantum dots. Here we report on the experimental evidence of motional narrowing in the optical spectrum of a semiconductor quantum dot broadened by the spectral diffusion phenomenon. Surprisingly, motional narrowing is achieved when decreasing incident power or temperature, in contrast with the standard phenomenology observed for nuclear magnetic resonance

Western European Populations of the Ichneumonid Wasp Hyposoter didymator Belong to a Single Taxon

Hyposoter didymator (Hymenoptera, Ichneumonidae) is a generalist solitary endoparasitoid of noctuid larvae. In the present work, we tested whether populations of H. didymator were divided in several genetically distinct taxa as described for many other generalist parasitoid species, and whether differences in H. didymator parasitism rates were explained by the insect host species and/or by the plant on which these hosts were feeding on. The genetic analysis of natural populations collected in different regions in France and Spain on seven different insect hosts and seven different host plants (775 individuals) showed that H. didymator populations belong to a unique single taxon. However, H. didymator seems to be somewhat specialized. Indeed, in the fields it more often parasitized Helicoverpa armigera compared to the other host species collected in the present work. Also, H. didymator parasitism rates in field conditions and semi-field experimental studies were dependent on the host plants on which H. armigera larvae are feeding. Still, H. didymator can occur occasionally on non-preferred noctuid species. One hypothesis explaining the ability of H. didymator to switch hosts in natura could be related to fluctuating densities of the preferred host over the year; this strategy would allow the parasitoid to avoid seasonal population collapses

10 simple rules to create a serious game, illustrated with examples from structural biology

Serious scientific games are games whose purpose is not only fun. In the field of science, the serious goals include crucial activities for scientists: outreach, teaching and research. The number of serious games is increasing rapidly, in particular citizen science games, games that allow people to produce and/or analyze scientific data. Interestingly, it is possible to build a set of rules providing a guideline to create or improve serious games. We present arguments gathered from our own experience ( Phylo , DocMolecules , HiRE-RNA contest and Pangu) as well as examples from the growing literature on scientific serious games

Enteric Neurospheres Are Not Specific to Neural Crest Cultures: Implications for Neural Stem Cell Therapies

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited

The Necrotic Signal Induced by Mycophenolic Acid Overcomes Apoptosis-Resistance in Tumor Cells

The amount of inosine monophosphate dehydrogenase (IMPDH), a pivotal enzyme for the biosynthesis of the guanosine tri-phosphate (GTP), is frequently increased in tumor cells. The anti-viral agent ribavirin and the immunosuppressant mycophenolic acid (MPA) are potent inhibitors of IMPDH. We recently showed that IMPDH inhibition led to a necrotic signal requiring the activation of Cdc42.Herein, we strengthened the essential role played by this small GTPase in the necrotic signal by silencing Cdc42 and by the ectopic expression of a constitutive active mutant of Cdc42. Since resistance to apoptosis is an essential step for the tumorigenesis process, we next examined the effect of the MPA–mediated necrotic signal on different tumor cells demonstrating various mechanisms of resistance to apoptosis (Bcl2-, HSP70-, Lyn-, BCR-ABL–overexpressing cells). All tested cells remained sensitive to MPA–mediated necrotic signal. Furthermore, inhibition of IMPDH activity in Chronic Lymphocytic Leukemia cells was significantly more efficient at eliminating malignant cells than apoptotic inducers.These findings indicate that necrosis and apoptosis are split signals that share few if any common hub of signaling. In addition, the necrotic signaling pathway induced by depletion of the cellular amount of GTP/GDP would be of great interest to eliminate apoptotic-resistant tumor cells