1,917 research outputs found
Fat storage-inducing transmembrane (FIT or FITM) proteins are related to lipid phosphatase/phosphotransferase enzymes
Fat storage-inducing transmembrane (FIT or FITM) proteins have been implicated in the partitioning of triacylglycerol to lipid droplets and the budding of lipid droplets from the ER. At the molecular level, the sole relevant interaction is that FITMs directly bind to triacyglycerol and diacylglycerol, but how they function at the molecular level is not known.Saccharomyces cerevisiaehas two FITM homologues: Scs3p and Yft2p. Scs3p was initially identified because deletion leads to inositol auxotrophy, with an unusual sensitivity to addition of choline. This strongly suggests a role for Scs3p in phospholipid biosynthesis. Looking at the FITM family as widely as possible, we found that FITMs are widespread throughout eukaryotes, indicating presence in the last eukaryotic common ancestor. Protein alignments also showed that FITM sequences contain the active site of lipid phosphatase/phosphotransferase (LPT) enzymes. This large family transfers phosphate-containing headgroups either between lipids or in exchange for water. We confirmed the prediction that FITMs are related to LPTs by showing that single amino-acid substitutions in the presumptive catalytic site prevented their ability to rescue growth of the mutants on low inositol/high choline media when over-expressed. The substitutions also prevented rescue of other phenotypes associated with loss of FITM in yeast, including mistargeting of Opi1p, defective ER morphology, and aberrant lipid droplet budding. These results suggest that Scs3p, Yft2p and FITMs in general are LPT enzymes involved in an as yet unknown critical step in phospholipid metabolism
Squeezed light from spin squeezed atoms
We propose to produce pulses of strongly squeezed light by Raman scattering
of a strong laser pulse on a spin squeezed atomic sample. We prove that the
emission is restricted to a single field mode which perfectly inherits the
quantum correlations of the atomic system.Comment: 5 pages, 2 figures, revtex4 beta
Integrin activation - the importance of a positive feedback
Integrins mediate cell adhesion and are essential receptors for the
development and functioning of multicellular organisms. Integrin activation is
known to require both ligand and talin binding and to correlate with cluster
formation but the activation mechanism and precise roles of these processes are
not yet resolved. Here mathematical modeling, with known experimental
parameters, is used to show that the binding of a stabilizing factor, such as
talin, is alone insufficient to enable ligand-dependent integrin activation for
all observed conditions; an additional positive feedback is required.Comment: in press in Bulletin of Mathematical Biolog
Equality of Participation Online Versus Face to Face: Condensed Analysis of the Community Forum Deliberative Methods Demonstration
Online deliberation may provide a more cost-effective and/or less inhibiting
environment for public participation than face to face (F2F). But do online
methods bias participation toward certain individuals or groups? We compare F2F
versus online participation in an experiment affording within-participants and
cross-modal comparisons. For English speakers required to have Internet access
as a condition of participation, we find no negative effects of online modes on
equality of participation (EoP) related to gender, age, or educational level.
Asynchronous online discussion appears to improve EoP for gender relative to
F2F. Data suggest a dampening effect of online environments on black
participants, as well as amplification for whites. Synchronous online voice
communication EoP is on par with F2F across individuals. But individual-level
EoP is much lower in the online forum, and greater online forum participation
predicts greater F2F participation for individuals. Measured rates of
participation are compared to self-reported experiences, and other findings are
discussed.Comment: 14 pages, 10 tables, to appear in Efthimios Tambouris, Panos
Panagiotopoulos, {\O}ystein S{\ae}b{\o}, Konstantinos Tarabanis, Michela
Milano, Theresa Pardo, and Maria Wimmer (Editors), Electronic Participation:
Proceedings of the 7th IFIP WG 8.5 International Conference, ePart 2015
(Thessaloniki, August 30-September 2), Springer LNCS Vol. 9249, 201
Coherent control using adaptive learning algorithms
We have constructed an automated learning apparatus to control quantum
systems. By directing intense shaped ultrafast laser pulses into a variety of
samples and using a measurement of the system as a feedback signal, we are able
to reshape the laser pulses to direct the system into a desired state. The
feedback signal is the input to an adaptive learning algorithm. This algorithm
programs a computer-controlled, acousto-optic modulator pulse shaper. The
learning algorithm generates new shaped laser pulses based on the success of
previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten
Tackling the jelly web: Trophic ecology of gelatinous zooplankton in oceanic food webs of the eastern tropical Atlantic assessed by stable isotope analysis
Gelatinous zooplankton can be present in high biomass and taxonomic diversity in planktonic oceanic food webs, yet the trophic structuring and importance of this “jelly web” remain incompletely understood. To address this knowledge gap, we provide a holistic trophic characterization of a jelly web in the eastern tropical Atlantic, based on δ13C and δ15N stable isotope analysis of a unique gelatinous zooplankton sample set. The jelly web covered most of the isotopic niche space of the entire planktonic oceanic food web, spanning > 3 trophic levels, ranging from herbivores (e.g., pyrosomes) to higher predators (e.g., ctenophores), highlighting the diverse functional roles and broad possible food web relevance of gelatinous zooplankton. Among gelatinous zooplankton taxa, comparisons of isotopic niches pointed to the presence of differentiation and resource partitioning, but also highlighted the potential for competition, e.g., between hydromedusae and siphonophores. Significant differences in spatial (seamount vs. open ocean) and depth‐resolved patterns (0–400 m vs. 400–1000 m) pointed to additional complexity, and raise questions about the extent of connectivity between locations and differential patterns in vertical coupling between gelatinous zooplankton groups. Added complexity also resulted from inconsistent patterns in trophic ontogenetic shifts among groups. We conclude that the broad trophic niche covered by the jelly web, patterns in niche differentiation within this web, and substantial complexity at the spatial, depth, and taxon level call for a more careful consideration of gelatinous zooplankton in oceanic food web models. In light of climate change and fishing pressure, the data presented here also provide a valuable baseline against which to measure future trophic observations of gelatinous zooplankton communities in the eastern tropical Atlantic
Beam-target helicity asymmetry for γ→n→→π−p in the N*resonance region
We report the first beam-target double-polarization asymmetries in the γ þ nðpÞ → π− þ pðpÞ reaction
spanning the nucleon resonance region from invariant mass W ¼ 1500 to 2300 MeV. Circularly polarized
photons and longitudinally polarized deuterons in solid hydrogen deuteride (HD) have been used with the
CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The exclusive final state has been
extracted using three very different analyses that show excellent agreement, and these have been used to
deduce the E polarization observable for an effective neutron target. These results have been incorporated
into new partial wave analyses and have led to significant revisions for several γnN* resonance
photocouplings
Comment on the narrow structure reported by Amaryan et al
The CLAS Collaboration provides a comment on the physics interpretation of
the results presented in a paper published by M. Amaryan et al. regarding the
possible observation of a narrow structure in the mass spectrum of a
photoproduction experiment.Comment: to be published in Physical Review
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