272 research outputs found
Molecular super-gluing: a straightforward tool for antibody labelling and its application to mycotoxin biosensing
Mycotoxins are low molecular weight toxic compounds, which can cause severe health problems in animals and humans. Immunoassays allow rapid, simple and cost-efective screening of mycotoxins. Sandwich assays with a direct readout provide great improvement in terms of selectivity and sensitivity, compared to the widely used competitive assay formats, for the analysis of low molecular weight molecules. In this work, we report a non-competitive fuorescence anti-immune complex (IC) immunoassay, based on the specifc recognition of HT-2 toxin with a pair of recombinant antibody fragments, namely antigen-binding fragment (Fab) (anti-HT-2 (10) Fab) and single-chain variable fragment (scFv) (anti-IC HT-2 (10) scFv). The SpyTag and SpyCatcher glue proteins were applied for the frst time as a bioconjugation tool for the analysis of mycotoxins. To this aim, a SpyTag-mScarlet-I (fuorescent protein) and scFv-SpyCatcher fusion proteins were constructed, produced and fused in situ during the assay by spontaneous Tag-Catcher binding. The assay showed an excellent sensitivity with an EC50 of 4.8±0.4 ng mL−1 and a dynamic range from 1.7±0.3 to 13±2 ng mL−1, an inter-day reproducibility of 8.5% and a high selectivity towards HT-2 toxin without cross-reactivity with other Fusarium toxins. The bioassay was applied to the analysis of the toxin in an oat reference material and in oat samples, with a LOD of 0.6 µg kg−1, and the results were validated by analysing a certifcate reference material and by HPLC–MS/MS
Liver-specific insulin receptor isoform A expression enhances hepatic glucose uptake and ameliorates liver steatosis in a mouse model of diet-induced obesity
Among the main complications associated with obesity are insulin
resistance and altered glucose and lipid metabolism within the liver. It
has previously been described that insulin receptor isoform A (IRA)
favors glucose uptake and glycogen storage in hepatocytes compared
with isoform B (IRB), improving glucose homeostasis in mice lacking
liver insulin receptor. Thus, we hypothesized that IRA could also
improve glucose and lipid metabolism in a mouse model of high-fatdiet-induced obesity. We addressed the role of insulin receptor
isoforms in glucose and lipid metabolism in vivo. We expressed IRA
or IRB specifically in the liver by using adeno-associated viruses
(AAVs) in a mouse model of diet-induced insulin resistance and
obesity. IRA, but not IRB, expression induced increased glucose
uptake in the liver and muscle, improving insulin tolerance. Regarding
lipid metabolism, we found that AAV-mediated IRA expression also
ameliorated hepatic steatosis by decreasing the expression of Fasn,
Pgc1a, Acaca and Dgat2 and increasing Scd-1 expression. Taken
together, our results further unravel the role of insulin receptor isoforms
in hepatic glucose and lipid metabolism in an insulin-resistant scenario.
Our data strongly suggest that IRA is more efficient than IRB at favoring
hepatic glucose uptake, improving insulin tolerance and ameliorating
hepatic steatosis. Therefore, we conclude that a gene therapy
approach for hepatic IRA expression could be a safe and promising
tool for the regulation of hepatic glucose consumption and lipid
metabolism, two key processes in the development of non-alcoholic
fatty liver disease associated with obesity
Explosive percolation yields highly-conductive polymer nanocomposites
Explosive percolation is an experimentally-elusive phenomenon where network connectivity coincides with onset of an additional modification of the system; materials with correlated localisation of percolating particles and emergent conductive paths can realise sharp transitions and high conductivities characteristic of the explosively-grown network. Nanocomposites present a structurally- and chemically-varied playground to realise explosive percolation in practically-applicable systems but this is yet to be exploited by design. Herein, we demonstrate composites of graphene oxide and synthetic polymer latex which form segregated networks, leading to low percolation threshold and localisation of conductive pathways. In situ reduction of the graphene oxide at temperatures of <150 °C drives chemical modification of the polymer matrix to produce species with phenolic groups, which are known crosslinking agents. This leads to conductivities exceeding those of dense-packed networks of reduced graphene oxide, illustrating the potential of explosive percolation by design to realise low-loading composites with dramatically-enhanced electrical transport properties
Challenge 1: Past global changes: a context to the Anthropocene
Facing current climate and environmental
crises needs long-term series of Earth
Dynamics and anthropogenic pressures on the
Planet. Numerous geological, chemical and
biological natural archives capture large-scale,
multi-temporal, abrupt, and often irreversible
shifts in environmental and climate systems,
providing an opportunity to better understand
and therefore predict potential future impacts
of the present anthropogenic warming and
Humankind impact on the Planet. By providing
robust, reliable, quantitative, detailed,
high-resolution and long paleoclimate and
paleoenvironmental data series,
paleoclimatology and paleoenvironmental
research place present climate variability and
ecological crises in a long-term perspective to
understand climate forcing mechanisms and
environmental processes and responses. The
success of science-based solutions to the global
risks in the 21st century will strongly rely on our
capacity to transfer this knowledge to
politicians, managers, and society.Peer reviewe
Extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens
Galaxy-cluster gravitational lenses can magnify background galaxies by a total factor of up to ~50. Here we report an image of an individual star at redshift z = 1.49 (dubbed MACS J1149 Lensed Star 1) magnified by more than ×2,000. A separate image, detected briefly 0.26″ from Lensed Star 1, is probably a counterimage of the first star demagnified for multiple years by an object of ≳3 solar masses in the cluster. For reasonable assumptions about the lensing system, microlensing fluctuations in the stars’ light curves can yield evidence about the mass function of intracluster stars and compact objects, including binary fractions and specific stellar evolution and supernova models. Dark-matter subhaloes or massive compact objects may help to account for the two images’ long-term brightness ratio
Arm and interarm abundance gradients in CALIFA spiral galaxies
Spiral arms are the most singular features in disc galaxies. These structures can exhibit different patterns, namely grand design and flocculent arms, with easily distinguishable characteristics. However, their origin and the mechanisms shaping them are unclear. The overall role of spirals in the chemical evolution of disc galaxies is another unsolved question. In particular, it has not been fully explored if the H ii regions of spiral arms present different properties from those located in the interarm regions. Here we analyse the radial oxygen abundance gradient of the arm and interarm star forming regions of 63 face-on spiral galaxies using CALIFA Integral Field Spectroscopy data. We focus the analysis on three characteristic parameters of the profile: slope, zero-point, and scatter. The sample is morphologically separated into flocculent versus grand design spirals and barred versus unbarred galaxies. We find subtle but statistically significant differences betweenthe arm and interarm distributions for flocculent galaxies, suggesting that the mechanisms generating the spiral structure in these galaxies may be different to those producing grand design systems, for which no significant differences are found. We also find small differences in barred galaxies, not observed in unbarred systems, hinting that bars may affect the chemical distribution of these galaxies but not strongly enough as to be reflected in the overall abundance distribution. In light of these results, we propose bars and flocculent structure as two distinct mechanisms inducing differences in the abundance distribution between arm and interarm star forming regions
WEAVE-StePS. A stellar population survey using WEAVE at WHT
The upcoming new generation of optical spectrographs on four-meter-class
telescopes will provide valuable opportunities for forthcoming galaxy surveys
through their huge multiplexing capabilities, excellent spectral resolution,
and unprecedented wavelength coverage. WEAVE is a new wide-field spectroscopic
facility mounted on the 4.2 m William Herschel Telescope in La Palma.
WEAVE-StePS is one of the five extragalactic surveys that will use WEAVE during
its first five years of operations. It will observe galaxies using WEAVE MOS
(~950 fibres across a field of view of ~3 deg2 on the sky) in low-resolution
mode (R~5000, spanning the wavelength range 3660-9590 AA). WEAVE-StePS will
obtain high-quality spectra (S/N ~ 10 per AA at R~5000) for a magnitude-limited
(I_AB = 20.5) sample of ~25,000 galaxies, the majority selected at z>=0.3. The
survey goal is to provide precise spectral measurements in the crucial interval
that bridges the gap between LEGA-C and SDSS data. The wide area coverage of
~25 deg2 will enable us to observe galaxies in a variety of environments. The
ancillary data available in each observed field (including X-ray coverage,
multi-narrow-band photometry and spectroscopic redshift information) will
provide an environmental characterisation for each observed galaxy. This paper
presents the science case of WEAVE-StePS, the fields to be observed, the parent
catalogues used to define the target sample, and the observing strategy chosen
after a forecast of the expected performance of the instrument for our typical
targets. WEAVE-StePS will go back further in cosmic time than SDSS, extending
its reach to encompass more than ~6 Gyr, nearly half of the age of the
Universe. The spectral and redshift range covered by WEAVE-StePS will open a
new observational window by continuously tracing the evolutionary path of
galaxies in the largely unexplored intermediate-redshift range.Comment: 15 pages, 9 figures, A&A in pres
- …