1,079 research outputs found
Conformational photoswitching of a synthetic peptide foldamer bound within a phospholipid bilayer
The dynamic properties of foldamers, synthetic molecules that mimic folded biomolecules, have mainly been explored in free solution.We report on the design, synthesis, and conformational behavior of photoresponsive foldamers bound in a phospholipid bilayer akin to a biological membrane phase. These molecules contain a chromophore, which can be switched between two configurations by different wavelengths of light, attached to a helical synthetic peptide that both promotes membrane insertion and communicates conformational change along its length. Light-induced structural changes in the chromophore are translated into global conformational changes, which are detected by monitoring the solid-state 19 F nuclear magnetic resonance signals of a remote fluorine-containing residue located 1 to 2 nanometers away. The behavior of the foldamers in the membrane phase is similar to that of analogous compounds in organic solvents
U-Pb SHRIMP zircon dating of andesite from the Dolomite area (NE Italy): geochronological evidence for the early onset of Permian Volcanism in the eastern part of the southern Alps
The Athesian Volcanic District (AVD), a thick sequence of andesitic to rhyolitic lava and ignimbrite, overlies both the Variscan basement of the Dolomites and, where present, the continental basal conglomerate of Upper Carboniferous(?) to Early Permian age. This volcanic activity is known to mark the margin of the intra-Pangea megashear system between Gondwana and Laurasia, the onset age of which is determined in this study. SHRIMP U-Pb dating on zircon from Ponte Gardena/Waidbruck (Isarco/Eisack valley) basaltic andesite yields an age of 290.7 ± 3 Ma, providing the oldest record of andesite volcanic activity yet documented in the AVD. Two younger dates (279.9 ± 3.3 and 278.6 ± 3.1 Ma) obtained for the andesitic necks of M. dei Ginepri (Eores/Aferer valley) and Col Quaterna (western Comelico), respectively, probably represent a second pulse of andesite magmatic activity. Near Chiusa/Klausen, the volcanoclastic deposits at the bottom of the Funes/Villnoss valley volcano-sedimentary complex only contain detrital zircons, dated at 469 ± 6 Ma; these probably derive from erosion of Paleozoic porphyroids. Other zircons from the same sediments and inherited cores of magmatic andesite crystals give Paleoproterozoic (1953.6 ± 22.1, 1834.6 ± 69.3, 1773.6 ± 25.1 Ma), Early Neoproterozoic (1015 ± 14 Ma) and Late Neoproterozoic (728.4 ± 9.6, 687.6 ± 7.6 Ma) ages. These ancient detrital and inherited zircon ages fit the model that envisages the Dolomite region as being tectonically coherent with Africa, at least until the Lower Permian
Laboratory Exposures to Staphylococcal Enterotoxin B
First report of symptoms after ocular exposure to staphylococcal enteroxin B in the laboratory is detailed
Glitches in rotating supersolids
Glitches, spin-up events in neutron stars, are of prime interest as they
reveal properties of nuclear matter at subnuclear densities. We numerically
investigate the glitch mechanism due to vortex unpinning using analogies
between neutron stars and dipolar supersolids. We explore the vortex and
crystal dynamics during a glitch and its dependence on the supersolid quality,
providing a tool to study glitches from different radial depths of a neutron
star. Benchmarking our theory against neutron star observations, our work will
open a new avenue for the quantum simulation of stellar objects from Earth.Comment: 13 pages, 9 figure
Sanitary problems related to the presence of Ostreopsis spp. in the Mediterranean Sea: a multidisciplinary scientific approach
The increased presence of potentially toxic microalgae in the Mediterranean area is a matter of great concern. Since the end of the last century, microalgae of the genus Ostreopsis have been detected more and more frequently in the Italian coastal waters. The presence of Ostreopsis spp. has been accompanied by the presence of previously undetected marine biotoxins (palytoxins) into the ecosystem with the increased possibility of human exposure. In response to the urgent need for toxicity characterization of palytoxin and its congeners, an integrated study encompassing both in vitro and in vivo methods was performed
Observation of vortices in a dipolar supersolid
Supersolids are states of matter that spontaneously break two continuous
symmetries: translational invariance due to the appearance of a crystal
structure and phase invariance due to phase locking of single-particle wave
functions, responsible for superfluid phenomena. While originally predicted to
be present in solid helium, ultracold quantum gases provided a first platform
to observe supersolids, with particular success coming from dipolar atoms.
Phase locking in dipolar supersolids has been probed through e.g. measurements
of the phase coherence and gapless Goldstone modes, but quantized vortices, a
hydrodynamic fingerprint of superfluidity, have not yet been observed. Here,
with the prerequisite pieces at our disposal, namely a method to generate
vortices in dipolar gases and supersolids with two-dimensional crystalline
order, we report on the theoretical investigation and experimental observation
of vortices in the supersolid phase. Our work reveals a fundamental difference
in vortex seeding dynamics between unmodulated and modulated quantum fluids.
This opens the door to study the hydrodynamic properties of exotic quantum
systems with multiple spontaneously broken symmetries, in disparate domains
such as quantum crystals and neutron stars.Comment: 14 pages, 9 figure
Observation of vortices and vortex stripes in a dipolar Bose-Einstein condensate
Quantized vortices are the prototypical feature of superfluidity. Pervasive
in all natural systems, vortices are yet to be observed in dipolar quantum
gases. Here, we exploit the anisotropic nature of the dipole-dipole interaction
of a dysprosium Bose-Einstein condensate to induce angular symmetry breaking in
an otherwise cylindrically symmetric pancake-shaped trap. Tilting the magnetic
field towards the radial plane deforms the cloud into an ellipsoid through
magnetostriction, which is then set into rotation. At stirring frequencies
approaching the radial trap frequency, we observe the generation of dynamically
unstable surface excitations, which cause angular momentum to be pumped into
the system through vortices. Under continuous rotation, the vortices arrange
into a stripe configuration along the field--in close corroboration with
simulations--realizing a long sought-after prediction for dipolar vortices.Comment: 13 pages, 4+3 figure
Toxicity and pathophysiology of palytoxin congeners after intraperitoneal and aerosol administration in rats
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Toxicon 150 (2018): 235-250, doi:10.1016/j.toxicon.2018.06.067.Preparations of palytoxin (PLTX, derived from Japanese Palythoa tuberculosa) and the congeners
42-OH-PLTX (from Hawaiian P. toxica) and ovatoxin-a (isolated from a Japanese strain of
Ostreopsis ovata), as well as a 50:50 mixture of PLTX and 42-OH-PLTX derived from Hawaiian P.
tuberculosa were characterized as to their concentration, composition, in-vitro potency and
interaction with an anti-PLTX monoclonal antibody (mAb), after which they were evaluated for
lethality and pathophysiological effects by intraperitoneal (IP) and aerosol administration to rats.
Once each preparation was characterized as to its toxin composition by LC-HRMS and normalized to
a total PLTX/OVTX concentration using HPLC-UV, all four preparations showed similar potency
towards mouse erythrocytes in the erythrocyte hemolysis assay and interactions with the anti-PLTX
mAb. The IP LD50 values derived from these experiments (1-3 μg/kg for all) were consistent with
published values, although some differences from the published literature were seen. The aerosol
LD50 values (.03-.06 μg/kg) confirmed the exquisite potency of PLTX suggested by the
literature. The pathophysiological effects of the different toxin preparations by IP and aerosol
administration were similar, albeit with some differences. Most commonly affected tissues were
the lungs, liver, heart, kidneys, salivary glands, and adrenal glands. Despite some differences,
these results suggest commonalities in potency and mechanism of action among these PLTX
congeners.This work was supported by the Defense Threat Reduction Agency, through the Joint
Program Executive Office for Chemical and Biological Defense, Contract number CB10396.
Additional support to DMA and DLK was provided by National Science Foundation (Grant
OCE-1314642) and National Institutes of Health (NIEHS-1P50-ES021923-01) through the
Woods Hole Center for Oceans and Human Health
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