Highly fluorescent guanosine mimics for folding and energy transfer studies

Guanosines with substituents at the 8-position can provide useful fluorescent probes that effectively mimic guanine residues even in highly demanding model systems such as polymorphic G-quadruplexes and duplex DNA. Here, we report the synthesis and photophysical properties of a small family of 8-substituted-2′-deoxyguanosines that have been incorporated into the human telomeric repeat sequence using phosphoramidite chemistry. These include 8-(2-pyridyl)-2′-deoxyguanosine (2PyG), 8-(2-phenylethenyl)-2′-deoxyguanosine (StG) and 8-[2-(pyrid-4-yl)-ethenyl]-2′-deoxyguanosine (4PVG). On DNA folding and stability, 8-substituted guanosines can exhibit context-dependent effects but were better tolerated by G-quadruplex and duplex structures than pyrimidine mismatches. In contrast to previously reported fluorescent guanine analogs, 8-substituted guanosines exhibit similar or even higher quantum yields upon their incorporation into nucleic acids (Φ = 0.02–0.45). We have used these highly emissive probes to quantify energy transfer efficiencies from unmodified DNA nucleobases to 8-substituted guanosines. The resulting DNA-to-probe energy transfer efficiencies (ηt) are highly structure selective, with ηt(duplex) < ηt(single-strand) < ηt(G-quadruplex). These trends were independent of the exact structural features and thermal stabilities of the G-quadruplexes or duplexes containing them. The combination of efficient energy transfer, high probe quantum yield, and high molar extinction coefficient of the DNA provides a highly sensitive and reliable readout of G-quadruplex formation even in highly diluted sample solutions of 0.25 nM

Transcriptome of Aphanomyces euteiches: New Oomycete Putative Pathogenicity Factors and Metabolic Pathways

Aphanomyces euteiches is an oomycete pathogen that causes seedling blight and root rot of legumes, such as alfalfa and pea. The genus Aphanomyces is phylogenically distinct from well-studied oomycetes such as Phytophthora sp., and contains species pathogenic on plants and aquatic animals. To provide the first foray into gene diversity of A. euteiches, two cDNA libraries were constructed using mRNA extracted from mycelium grown in an artificial liquid medium or in contact to plant roots. A unigene set of 7,977 sequences was obtained from 18,864 high-quality expressed sequenced tags (ESTs) and characterized for potential functions. Comparisons with oomycete proteomes revealed major differences between the gene content of A. euteiches and those of Phytophthora species, leading to the identification of biosynthetic pathways absent in Phytophthora, of new putative pathogenicity genes and of expansion of gene families encoding extracellular proteins, notably different classes of proteases. Among the genes specific of A. euteiches are members of a new family of extracellular proteins putatively involved in adhesion, containing up to four protein domains similar to fungal cellulose binding domains. Comparison of A. euteiches sequences with proteomes of fully sequenced eukaryotic pathogens, including fungi, apicomplexa and trypanosomatids, allowed the identification of A. euteiches genes with close orthologs in these microorganisms but absent in other oomycetes sequenced so far, notably transporters and non-ribosomal peptide synthetases, and suggests the presence of a defense mechanism against oxidative stress which was initially characterized in the pathogenic trypanosomatids

Huntington's disease: a clinical review

Huntington's disease (HD) is a fully penetrant neurodegenerative disease caused by a dominantly inherited CAG trinucleotide repeat expansion in the huntingtin gene on chromosome 4. In Western populations HD has a prevalence of 10.6-13.7 individuals per 100,000. It is characterised by cognitive, motor and psychiatric disturbance. At the cellular level mutant huntingtin results in neuronal dysfunction and death through a number of mechanisms, including disruption of proteostasis, transcription and mitochondrial function and direct toxicity of the mutant protein. Early macroscopic changes are seen in the striatum with involvement of the cortex as the disease progresses. There are currently no disease modifying treatments therefore supportive and symptomatic management is the mainstay of treatment. In recent years there have been significant advances in understanding both the cellular pathology and the macroscopic structural brain changes that occur as the disease progresses. In the last decade there has been a large growth in potential therapeutic targets and clinical trials. Perhaps the most promising of these are the emerging therapies aimed at lowering levels of mutant huntingtin. Antisense oligonucleotide therapy is one such approach with clinical trials currently underway. This may bring us one step closer to treating and potentially preventing this devastating condition

Functionalization of Gold Nanoparticles by Inorganic Entities

International audienceThe great affinity of gold surface for numerous electron-donating groups has largely contributed to the rapid development of functionalized gold nanoparticles (Au-NPs). In the last years, a new subclass of nanocomposite has emerged, based on the association of inorganic molecular entities (IME) with Au-NPs. This highly extended and diversified subclass was promoted by the synergy between the intrinsic properties of the shell and the gold core. This review-divided into four main parts-focuses on an introductory section of the basic notions related to the stabilization of gold nanoparticles and defines in a second part the key role played by the functionalizing agent. Then, we present a wide range of inorganic molecular entities used to prepare these nanocomposites (NCs). In particular, we focus on four different types of inorganic systems, their topologies, and their current applications. Finally, the most recent applications are described before an overview of this new emerging field of research

Des trous dans l’architecture des matériaux

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Interfacing metal organic frameworks with polymers or carbon-based materials: from simple to hierarchical porous and nanostructured composites

International audienceThe article covers the survey of recent progress in the design of MOFs–polymers and MOF–carbon material composites with increasing complexity in terms of porous architecture, spatial structuration, organisation, and functionality

Efficient syntheses of thiophenol derivatives

International audienceThe photochemical bromination of 4-methylthiophenol with N-bromosuccinimide is reported. Depending on the amount of NBS, mono or bis bromination of the methyl group was obtained. Conversion of brominated derivatives to dialdehydes is also discussed. Improvement of synthetic routes towards thiophenol derivatives is motivated by their key role for the functionalization of metal nanoparticles and surface