86 research outputs found

    Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

    Get PDF
    We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.

    Genotyping a second growth coast redwood forest : a high throughput methodology

    Get PDF
    The idea that excitonic (electronic) coherences are of fundamental importance to natural photosynthesis gained popularity when slowly dephasing quantum beats (QBs) were observed in the two-dimensional electronic spectra of the Fenna–Matthews–Olson (FMO) complex at 77 K. These were assigned to superpositions of excitonic states, a controversial interpretation, as the strong chromophore–environment interactions in the complex suggest fast dephasing. Although it has been pointed out that vibrational motion produces similar spectral signatures, a concrete assignment of these oscillatory signals to distinct physical processes is still lacking. Here we revisit the coherence dynamics of the FMO complex using polarization-controlled two-dimensional electronic spectroscopy, supported by theoretical modelling. We show that the long-lived QBs are exclusively vibrational in origin, whereas the dephasing of the electronic coherences is completed within 240 fs even at 77 K. We further find that specific vibrational coherences are produced via vibronically coupled excited states. The presence of such states suggests that vibronic coupling is relevant for photosynthetic energy transfer

    A DISPOSABLE OPTICAL BIOSENSOR BASED ON TOTAL INTERNAL REFLECTION FLUORESCENCE

    No full text
    A novel disposable biosensor device is described, based on the generation of evanescent light waves at an optical interface. The sensor is injection moulded from high optical quality plastic and consists of two parts, the waveguide and a cuvette for containing the sample solution. Antigens are attached to the waveguide surface and the reaction with antibodies is monitored by exciting and collecting fluorescent light "back-tunneled" out of the waveguide. A model assay for human IgG is used to demonstrate that this biosensor can give rapid, sensitive results

    Identification and multi-environment validation of resistance to Ascochyta fabae in faba bean (Vicia faba)

    No full text
    Ascochyta blight incited by Ascochyta fabae is a widespread disease severely damaging faba bean (Vicia faba) production. Insufficient resistance is available in faba bean cultivars. In an attempt to identify new sources of resistance a germplasm collection of 484 V. faba accessions was screened for resistance to A. fabae under field conditions; stability of resistance of the 19 most resistant accessions was tested in a multi-location experiment in Czech Republic, Estonia, Germany and Spain over two field seasons. Although complete resistance was not found, six accessions showed interesting levels of incomplete resistance. Genotype. ×. environment (G. ×. E) interaction accounted for 42% of the sum of squares of the multi-environment evaluation, revealing instability of the phenotypic expression across environments. Accessions L-831818, V-26 and V-958 stand out for their consistent resistance, being the most resistant and stable across environments. Accessions V-255, V-1020, V-1085 and V-1117 displayed good resistance, but lower stability, with V-1020, V-1085 and V-1117 being more suitable for Córdoba (Mediterranean mega-environment), and V-255 more suitable for Hohenlieth, Jõgeva and Sumperk (Continental mega-environment). © 2011 Elsevier B.V.Financial support by the European Union EUFABA project (ref. QLK5-CT2002-02307) is acknowledged.Peer Reviewe

    Adaptation of spring faba bean types across European climates

    No full text
    International audienceFaba bean (Vicia faba L) is a cool season grain legume whose acreage has constantly declined in traditional producer countries as it has been replaced by more productive cereal crops. However, faba bean is still considered to have great potential as rainfed crop. In order to satisfy the renewed interest in faba bean cultivation yield stability should be improved by exploiting different germplasm types and sowing seasons. In order to understand of genotype by environment interactions and to compare cultivar performance over years and locations a spring faba bean network was established with 20 cultivars grown over three crop seasons at 13 contrasting locations covering most of Europe. Analysis was performed by heritability-adjusted genotype plus genotype x environment interaction (HA-GGE) biplot analysis. HA-GGE biplot analyses identified that the effect of genotype by environment interaction was higher than the effect of genotypes, allowing identification of three mega-environments, namely Continental, Oceanic, and Mediterranean, in which cultivar performed differently. This supports the need for specific breeding for each specific geoclimatic area. Espresso was the highest yielding cultivar, being also highly stable over the Oceanic and Continental mega-environments. Cultivars Fuego, Hobbit and SR-1060 had also good yield but with a moderate unstability in both Oceanic and Continental mega-environments. Baraca and Alameda yielded poorly at all environments although were the best yielders at Mediterranean locations. Environments as Sumperk and Premesques were identified as the best core test locations for Continental and Oceanic mega-environments, respectively, being the locations in which best genotypes could be most easily identified. (C) 2013 Elsevier B.V. All rights reserved

    Genetic diversity in European Pisum germplasm collections

    Get PDF
    The distinctness of, and overlap between, pea genotypes held in several Pisum germplasm collections has been used to determine their relatedness and to test previous ideas about the genetic diversity of Pisum. Our characterisation of genetic diversity among 4,538 Pisum accessions held in 7 European Genebanks has identified sources of novel genetic variation, and both reinforces and refines previous interpretations of the overall structure of genetic diversity in Pisum. Molecular marker analysis was based upon the presence/absence of polymorphism of retrotransposon insertions scored by a high-throughput microarray and SSAP approaches. We conclude that the diversity of Pisum constitutes a broad continuum, with graded differentiation into sub-populations which display various degrees of distinctness. The most distinct genetic groups correspond to the named taxa while the cultivars and landraces of Pisum sativum can be divided into two broad types, one of which is strongly enriched for modern cultivars. The addition of germplasm sets from six European Genebanks, chosen to represent high diversity, to a single collection previously studied with these markers resulted in modest additions to the overall diversity observed, suggesting that the great majority of the total genetic diversity collected for the Pisum genus has now been described. Two interesting sources of novel genetic variation have been identified. Finally, we have proposed reference sets of core accessions with a range of sample sizes to represent Pisum diversity for the future study and exploitation by researchers and breeders. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-012-1839-1) contains supplementary material, which is available to authorized users
    corecore