498 research outputs found

    Fluorometabolite biosynthesis in streptomyces cattleya

    Get PDF
    Nature has evolved the ability to form a C-F bond, as exemplified by the bacterium Streptomyces cattleya, which elaborates fluoroacetate (FAc) and 4-fluorothreomne (4- FT). The mechanism of this bond formation are unknown. This thesis probes the biosynthesis of fluoroacetate and 4-fiuorothreonine and in doing so explores the C-F bond forming process. Feeding stable isotope enriched primary metabolites to S. cattleya, followed by (^19)F NMR and GCMS analysis of the resultant fluorometabolites, highlights the role of the glycolytic pathway in delivering a substrate for fluorination. 3-Fluoro-l- hydroxypropan-2-one was synthesised and feeding studies eliminate this as the initial product of fluorination. Fluoroacetaldehyde was identified as a common fluorinated intermediate in the biosynthesis of both FAc and 4-FT. Whole cell studies demonstrate the rapid oxidation of fluoroacetaldehyde to FAc. 4-FT is produced in low quantities by S. cattleya incubated with fluoroacetaldehyde. The synthesis and feeding of [1-(^2)H]- fluoroacetaldehyde provide evidence that the resultant 4-FT is biosynthesised from fluoroacetaldehyde. The biotransformation from fluoroacetaldehyde to FAc was shown in cell free studies to be mediated by an aldehyde dehydrogenase, requiring NAD(^4) as a co-factor. The substrate specificity of fluoroacetaldehyde dehydrogenase was probed by spectrophotometrically monitoring the production of NADH in the presence of different aldehydes. Further cell free experiments probed the biosynthetic origins of fluoroacetaldehyde. Glycolaldehyde phosphate and various phosphorylated glycolytic intermediates were incubated with cell free extracts of S. cattleya and a plethora of co-factors. In the absence of observing fluorination activity, it was shown that the cell free extract acts to dephosphorylate the substrates. The putative role of glycolaldehyde phosphate was explored by feeding isotopically labelled glycolaldehydes to whole cells of the bacterium. The results were not consistent with direct conversion from glycolaldehyde phosphate to fluoroacetaldehyde

    The Stargazin-Related Protein {gamma}7 Interacts with the mRNA-Binding Protein Heterogeneous Nuclear Ribonucleoprotein A2 and Regulates the Stability of Specific mRNAs, Including CaV2.2

    Get PDF
    The role(s) of the novel stargazin-like {gamma}-subunit proteins remain controversial. We have shown previously that the neuron-specific {gamma}7 suppresses the expression of certain calcium channels, particularly CaV2.2, and is therefore unlikely to operate as a calcium channel subunit. We now show that the effect of {gamma}7 on CaV2.2 expression is via an increase in the degradation rate of CaV2.2 mRNA and hence a reduction of CaV2.2 protein level. Furthermore, exogenous expression of {gamma}7 in PC12 cells also decreased the endogenous CaV2.2 mRNA level. Conversely, knockdown of endogenous {gamma}7 with short-hairpin RNAs produced a reciprocal enhancement of CaV2.2 mRNA stability and an increase in endogenous calcium currents in PC12 cells. Moreover, both endogenous and expressed {gamma}7 are present on intracellular membranes, rather than the plasma membrane. The cytoplasmic C terminus of {gamma}7 is essential for all its effects, and we show that {gamma}7 binds directly via its C terminus to a heterogeneous nuclear ribonucleoprotein (hnRNP A2), which also binds to a motif in CaV2.2 mRNA, and is associated with native CaV2.2 mRNA in PC12 cells. The expression of hnRNP A2 enhances CaV2.2 IBa, and this enhancement is prevented by a concentration of {gamma}7 that alone has no effect on IBa. The effect of {gamma}7 is selective for certain mRNAs because it had no effect on {alpha}2{delta}-2 mRNA stability, but it decreased the mRNA stability for the potassium-chloride cotransporter, KCC1, which contains a similar hnRNP A2 binding motif to that in CaV2.2 mRNA. Our results indicate that {gamma}7 plays a role in stabilizing CaV2.2 mRNA

    Modulation of cognitive performance and mood by aromas of peppermint and ylang-ylang

    Get PDF
    This study provides further evidence for the impact of the aromas of plant essential oils on aspects of cognition and mood in healthy participants. One hundred and forty-four volunteers were randomly assigned to conditions of ylang-ylang aroma, peppermint aroma, or no aroma control. Cognitive performance was assessed using the Cognitive Drug Research computerized assessment battery, with mood scales completed before and after cognitive testing. The analysis of the data revealed significant differences between conditions on a number of the factors underpinning the tests that constitute the battery. Peppermint was found to enhance memory whereas ylang-ylang impaired it, and lengthened processing speed. In terms of subjective mood peppermint increased alertness and ylang-ylang decreased it, but significantly increased calmness. These results provide support for the contention that the aromas of essential oils can produce significant and idiosyncratic effects on both subjective and objective assessments of aspects of human behavior. They are discussed with reference to possible pharmacological and psychological modes of influence

    Uncovering the origin of Z-configured double bonds in polyketides: intermediate E-double bond formation during borrelidin biosynthesis

    Get PDF
    Formation of Z-configured double bonds in reduced polyketides is uncommon and their origins have not been extensively studied. To investigate the origin of the Z-configured double bond in the macrolide borrelidin, the recombinant dehydratase domains BorDH2 and B0rDH3 were assayed with a synthetic analogue of the predicted tetraketide substrate. The configuration of the dehydrated products was determined to be E in both cases by comparison to synthetic standards. Detailed NMR spectroscopic analysis of the biosynthetic intermediate pre-borrelidin confirmed the E,E-configuration of the fulllength polyketide synthase product. In contrast to a previously-proposed hypothesis, our results show that in this case the Z-configured double bond is not formed via dehydration from a 3 L-configured precursor, but rather as the result of a later isomerization process.Marie Curie programme of the European UnionEmmy Noether programme of the Deutsche ForschungsgemeinschaftDAA

    High quality waveguides for the mid-infrared wavelength range in a silicon-on-sapphire platform

    Full text link
    We report record low loss silicon-on-sapphire nanowires for applications to mid infrared optics. We achieve propagation losses as low as 0.8dB/cm at 1550nm, 1.1 to 1.4dB/cm at 2080nm and < 2dB/cm at = 5.18 microns.Comment: 9 pages, 6 figures, 18 reference

    A new species of Protophyllocladoxylon from the Upper Cretaceous (Cenomanian-Turonian) portion of the Winton Formation, central-western Queensland, Australia

    Get PDF
    Leaf floras in fluvial-lacustrine sediments of the Upper Cretaceous (Cenomanian-Turonian) portion of the Winton Formation suggest a community with co-dominance of angiosperms, conifers, ginkgo and other seed plants. To date wood floras associated with the Winton Formation have not been examined in detail. Winton Formation wood has been presumed to comprise araucarian, podocarp and taxodiaceous components, but this has been based largely on the identification of other plant macro and microfossils. Here we describe a new species of podocarp fossil wood from the genus Protophyllodadoxylon based on eleven specimens of silicified wood found as surface material at two broadly coeval sites in the Cenomanian-Turonian portion of the Winton Formation: QM L311 and Bladensburg National Park. The new species is characterised by the presence of araucaroid tracheid pitting and phyllodadoid oopores, the absence of oculipores, and the paired arrangement of the oopores within the crossfields. The recognition of Protophyllocladoxylon in the Winton Formation supports previous palynological frequency counts that suggest a dominance of podocarp conifers. (C) 2014 Elsevier B.V. All rights reserved

    Intrinsic and extrinsic drivers of activity budgets in sympatric grey and harbour seals

    Get PDF
    D. J. F. Russell was funded by the UK Department of Energy and Climate Change (DECC) as part of their Offshore Energy Strategic Environmental Assessment programme and by Scottish Government as part of their Marine Mammal Scientific Support Research Programme (MMSS/001/11). The telemetry tags and their deployment were funded by DECC, the Natural Environment Research Council, Scottish Government, Marine Scotland Science and The European Commission.Investigation of activity budgets in relation to seasonal, intrinsic (age, sex) and extrinsic (time of day, spatial) covariates enables an understanding of how such covariates shape behavioural strategies. However, conducting such investigations in the wild is challenging, because of the required large sample size of individuals across the annual cycle, and difficulties in categorising behavioural states and analysing the resulting individual-referenced and serially correlated data. In this study, from telemetry tags deployed on 63 grey seals (Halichoerus grypus) and 126 harbour seals (Phoca vitulina) we used behavioural data, and movement data within a Bayesian state-space model (SSM), to define population-level activity budgets around Britain. Using generalised estimating equations (GEEs) we then examined how time spent in four states (resting on land (hauled out), resting at sea, foraging and travelling) was influenced by seasonal, intrinsic and extrinsic covariates. We present and discuss the following key findings. (1) We found no evidence that regional variation in foraging effort was linked to regional population trajectories in harbour seals. (2) Grey seals demonstrated sex-specific seasonal differences in their activity budgets, independent from those related to reproductive costs. (3) In these sympatric species there was evidence of temporal separation in time hauled out, but not in time foraging. (4) In both species, time spent resting at sea was separated into inshore (associated with tidal haul out availability) and offshore areas. Time spent resting at sea and on land was interchangeable to some extent, suggesting a degree of overlap in their functionality. This may result in a relaxation of the constraints associated with a central place foraging strategy. More generally, we demonstrate how a large dataset, incorporating differing tag parameters, can be analysed to define activity budgets and subsequently address important ecological questions.PostprintPeer reviewe

    Extended X-ray emission in PKS 1718-649

    Get PDF
    © ESO 2018. PKS 1718-649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718-649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton, we are able to study the detailed physics of the environment of PKS 1718-649. Not only can we confirm that the bulk of the kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate

    Salivary Biomarkers in a Biofilm Overgrowth Model

    Get PDF
    The purpose of this study was to determine whether baseline salivary inflammatory biomarkers could discriminate between different clinical levels of disease and/or predict clinical progression over a 3-week stent-induced biofilm overgrowth (SIBO) period
    • …
    corecore