24 research outputs found
First experimental evidence of one-dimensional plasma modes in superconducting thin wires
We have studied niobium superconducting thin wires deposited onto a
SrTiO substrate. By measuring the reflection coefficient of the wires,
resonances are observed in the superconducting state in the 130 MHz to 4 GHz
range. They are interpreted as standing wave resonances of one-dimensional
plasma modes propagating along the superconducting wire. The experimental
dispersion law, versus , presents a linear dependence over the
entire wave vector range. The modes are softened as the temperature increases
close the superconducting transition temperature. Very good agreement are
observed between our data and the dispersion relation predicted by Kulik and
Mooij and Sch\"on.Comment: Submitted to Physical review Letter
Reversing non-local transport through a superconductor by electromagnetic excitations
Superconductors connected to normal metallic electrodes at the nanoscale
provide a potential source of non-locally entangled electron pairs. Such states
would arise from Cooper pairs splitting into two electrons with opposite spins
tunnelling into different leads. In an actual system the detection of these
processes is hindered by the elastic transmission of individual electrons
between the leads, yielding an opposite contribution to the non-local
conductance. Here we show that electromagnetic excitations on the
superconductor can play an important role in altering the balance between these
two processes, leading to a dominance of one upon the other depending on the
spatial symmetry of these excitations. These findings allow to understand some
intriguing recent experimental results and open the possibility to control
non-local transport through a superconductor by an appropriate design of the
experimental geometry.Comment: 6 pages, 3 figure
Structural, functional and evolutionary analysis of the unusually large stilbene synthase gene family in grapevine (Vitis vinifera)
International audienc
Structural, functional and evolutionary analysis of the unusually large stilbene synthase gene family in grapevine (Vitis vinifera)
International audienc
Granuloma blastomicĂłtico na medula cervical: registro de um caso
Os autores apresentam um caso de blastomicose medular. O paciente apresentava sĂndrome de Brown-SĂ©quard. ApĂłs a mielografia foi submetido Ă laminectomia cervical. Na operação foi encontrada lesĂŁo tumoral que a histologia mostrou tratar-se de um granuloma blastomicĂłtico. O paciente foi medicado com Anfotericina B, associada Ă sulfametoxazol e trimetropim, assim como tratamento fisioterápico. A despeito do tratamento instituĂdo o paciente nĂŁo apresentou melhoras no que respeita Ă sintomatologia neurolĂłgica
Characterization of a second secologanin synthase isoform producing both secologanin and secoxyloganin allows enhanced de novo assembly of a Catharanthus roseus transcriptome
Background: Transcriptome sequencing offers a great resource for the study of non-model plants such as Catharanthus roseus, which produces valuable monoterpenoid indole alkaloids (MIAs) via a complex biosynthetic pathway whose characterization is still undergoing. Transcriptome databases dedicated to this plant were recently developed by several consortia to uncover new biosynthetic genes. However, the identification of missing steps in MIA biosynthesis based on these large datasets may be limited by the erroneous assembly of close transcripts and isoforms, even with the multiple available transcriptomes. Results: Secologanin synthases (SLS) are P450 enzymes that catalyze an unusual ring-opening reaction of loganin in the biosynthesis of the MIA precursor secologanin. We report here the identification and characterization in C. roseus of a new isoform of SLS, SLS2, sharing 97 % nucleotide sequence identity with the previously characterized SLS1. We also discovered that both isoforms further oxidize secologanin into secoxyloganin. SLS2 had however a different expression profile, being the major isoform in aerial organs that constitute the main site of MIA accumulation. Unfortunately, we were unable to find a current C. roseus transcriptome database containing simultaneously well reconstructed sequences of SLS isoforms and accurate expression levels. After a pair of close mRNA encoding tabersonine 16-hydroxylase (T16H1 and T16H2), this is the second example of improperly assembled transcripts from the MIA pathway in the public transcriptome databases. To construct a more complete transcriptome resource for C. roseus, we re-processed previously published transcriptome data by combining new single assemblies. Care was particularly taken during clustering and filtering steps to remove redundant contigs but not transcripts encoding potential isoforms by monitoring quality reconstruction of MIA genes and specific SLS and T16H isoforms. The new consensus transcriptome allowed a precise estimation of abundance of SLS and T16H isoforms, similar to qPCR measurements. Conclusions: The C. roseus consensus transcriptome can now be used for characterization of new genes of the MIA pathway. Furthermore, additional isoforms of genes encoding distinct MIA biosynthetic enzymes isoforms could be predicted suggesting the existence of a higher level of complexity in the synthesis of MIA, raising the question of the evolutionary events behind what seems like redundancy
Sarpagan bridge enzyme has substrate-controlled cyclization and aromatization modes
International audienceCyclization reactions that create complex polycyclic scaffolds are hallmarks of alkaloid biosynthetic pathways. We present the discovery of three homologous cytochrome P450s from three monoterpene indole alkaloid-producing plants (Rauwolfia serpentina, Gelsemium sempervirens and Catharanthus roseus) that provide entry into two distinct alkaloid classes, the sarpagans and the β-carbolines. Our results highlight how a common enzymatic mechanism, guided by related but structurally distinct substrates, leads to either cyclization or aromatization