30 research outputs found
A New Upper Limit for the Tau-Neutrino Magnetic Moment
Using a prompt neutrino beam in which a nu_tau component was identified for
the first time, the nu_tau magnetic moment was measured based on a search for
an anomalous increase in the number of neutrino-electron interactions. One such
event was observed when 2.3 were expected from background processes, giving an
upper 90% confidence limit of 3.9x10^-7 Bohr magnetons.Comment: 9 pages; 1 figur
A first measurement of the interaction cross section of the tau neutrino
The DONuT experiment collected data in 1997 and published first results in
2000 based on four observed charged-current (CC) interactions. The
final analysis of the data collected in the experiment is presented in this
paper, based on protons on target using the 800 GeV
Tevatron beam at Fermilab. The number of observed CC interactions is
9, from a total of 578 observed neutrino interactions. We calculated the
energy-independent part of the tau-neutrino CC cross section (), relative to the well-known and cross sections. The
ratio / was found to be
. The CC cross section was found to be cm. Both results are in
agreement the Standard Model.Comment: 37 pages, 15 figure
Observation of Tau Neutrino Interactions
The DONUT experiment has analyzed 203 neutrino interactions recorded in
nuclear emulsion targets. A decay search has found evidence of four tau
neutrino interactions with an estimated background of 0.34 events. This number
is consistent with the Standard Model expectation.Comment: 12 pages, 3 figures, PD
Membrane curvature in cell biology: An integration of molecular mechanisms.
Curving biological membranes establishes the complex architecture of the cell and mediates membrane traffic to control flux through subcellular compartments. Common molecular mechanisms for bending membranes are evident in different cell biological contexts across eukaryotic phyla. These mechanisms can be intrinsic to the membrane bilayer (either the lipid or protein components) or can be brought about by extrinsic factors, including the cytoskeleton. Here, we review examples of membrane curvature generation in animals, fungi, and plants. We showcase the molecular mechanisms involved and how they collaborate and go on to highlight contexts of curvature that are exciting areas of future research. Lessons from how membranes are bent in yeast and mammals give hints as to the molecular mechanisms we expect to see used by plants and protists
Modification of the spin structure of chromium by an interface effect in Cr(011)/Sn multilayers
Magnetic properties of thin chromium layers in Gd/Cr and Y/Cr multilayers studied using Sn-119 Mossbauer spectroscopy
Bovine F<sub>1</sub>F<sub>0</sub> ATP synthase monomers bend the lipid bilayer in 2D membrane crystals
We have used a combination of electron cryo-tomography, subtomogram averaging, and electron crystallographic image processing to analyse the structure of intact bovine F1Fo ATP synthase in 2D membrane crystals. ATPase assays and mass spectrometry analysis of the 2D crystals confirmed that the enzyme complex was complete and active. The structure of the matrix-exposed region was determined at 24 Å resolution by subtomogram averaging and repositioned into the tomographic volume to reveal the crystal packing. F1Fo ATP synthase complexes are inclined by 16° relative to the crystal plane, resulting in a zigzag topology of the membrane and indicating that monomeric bovine heart F1Fo ATP synthase by itself is sufficient to deform lipid bilayers. This local membrane curvature is likely to be instrumental in the formation of ATP synthase dimers and dimer rows, and thus for the shaping of mitochondrial cristae
Protein assemblies ejected directly from native membranes yield complexes for mass spectrometry
Membrane proteins reside in lipid bilayers and are typically extracted from this environment for study, which often compromises their integrity. In this work, we ejected intact assemblies from membranes, without chemical disruption, and used mass spectrometry to define their composition. From Escherichia coli outer membranes, we identified a chaperone-porin association and lipid interactions in the β-barrel assembly machinery. We observed efflux pumps bridging inner and outer membranes, and from inner membranes we identified a pentameric pore of TonB, as well as the protein-conducting channel SecYEG in association with F1FO adenosine triphosphate (ATP) synthase. Intact mitochondrial membranes from Bos taurus yielded respiratory complexes and fatty acid–bound dimers of the ADP (adenosine diphosphate)/ATP translocase (ANT-1). These results highlight the importance of native membrane environments for retaining small-molecule binding, subunit interactions, and associated chaperones of the membrane proteome