5,537 research outputs found
Charybdotoxin binding in the I(Ks) pore demonstrates two MinK subunits in each channel complex.
I(Ks) voltage-gated K(+) channels contain four pore-forming KCNQ1 subunits and MinK accessory subunits in a number that has been controversial. Here, I(Ks) channels assembled naturally by monomer subunits are compared to those with linked subunits that force defined stoichiometries. Two strategies that exploit charybdotoxin (CTX)-sensitive subunit variants are applied. First, CTX on rate, off rate, and equilibrium affinity are found to be the same for channels of monomers and those with a fixed 2:4 MinK:KCNQ1 valence. Second, 3H-CTX and an antibody are used to directly quantify channels and MinK subunits, respectively, showing 1.97 +/- 0.07 MinK per I(Ks) channel. Additional MinK subunits do not enter channels of monomeric subunits or those with fixed 2:4 valence. We conclude that two MinK subunits are necessary, sufficient, and the norm in I(Ks) channels. This stoichiometry is expected for other K(+) channels that contain MinK or MinK-related peptides (MiRPs)
A note on the effectiveness of selenium supplementation of Irish-grown Allium crops.
peer-reviewedThis study is funded by the Department of Agriculture and Food through the Network and Team Building Initiative of the Food Institutional Research Measure (FIRM Reference Number 06/NITARFC6).Onions and other Allium crops contain high levels of dietary phenolics and, unlike
many other crops, accumulate the beneficial mineral selenium. Selenium-enhanced
Allium crops are of interest both from a public good perspective and as a market
positioning strategy for growers. Field trials were carried out to i) identify onion and
scallion varieties that contain high levels of health-promoting phenolic and flavonoid
compounds as potential targets for selenium supplementation and ii) investigate selenium
supplementation in the widely-grown commercial onion variety ‘Hyskin’ at different
application rates of nitrogen fertilizer. Levels of selenium in onion bulbs were
significantly increased from 0.5–5.9 μg/g dry weight (DW) to 40.6–70.0 μg/g DW.Department of Agriculture, Food and the Marin
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Ito channels are octomeric complexes with four subunits of each Kv4.2 and K+ channel-interacting protein 2.
Mammalian voltage-gated K+ channels are assemblies of pore-forming alpha-subunits and modulating beta-subunits. To operate correctly, Kv4 alpha-subunits in the heart and central nervous system require recently identified beta-subunits of the neuronal calcium sensing protein family called K+ channel-interacting proteins (KChIPs). Here, Kv4.2.KChIP2 channels are purified, integrity of isolated complexes confirmed, molar ratio of the subunits determined, and subunit valence established. A complex has 4 subunits of each type, a stoichiometry expected for other channels employing neuronal calcium sensing beta-subunits
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Three-dimensional structure of I(to); Kv4.2-KChIP2 ion channels by electron microscopy at 21 Angstrom resolution.
Regulatory KChIP2 subunits assemble with pore-forming Kv4.2 subunits in 4:4 complexes to produce native voltage-gated potassium (Kv) channels like cardiac I(to) and neuronal I(A) subtypes. Here, negative stain electron microscopy (EM) and single particle averaging reveal KChIP2 to create a novel approximately 35 x 115 x 115 Angstrom, intracellular fenestrated rotunda: four peripheral columns that extend down from the membrane-embedded portion of the channel to enclose the Kv4.2 "hanging gondola" (a platform held beneath the transmembrane conduction pore by four internal columns). To reach the pore from the cytosol, ions traverse one of four external fenestrae to enter the rotundal vestibule and then cross one of four internal windows in the gondola
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THINC: A Remote Display Architecture for Thin-Client Computing
Rapid improvements in network bandwidth, cost, and ubiquity combined with the security hazards and high total cost of ownership of personal computers have created a growing market for thin-client computing. We introduce THINC, a remote display system architecture for high-performance thin-client computing in both LAN and WAN environments. THINC transparently maps high-level application display calls to a few simple low-level commands which can be implemented easily and efficiently. THINC introduces a number of novel latency-sensitive optimization techniques, including offscreen drawing awareness, command buffering and scheduling, non-blocking display operation, native video support, and server-side screen scaling. We have implemented THINC in an XFree86/Linux environment and compared its performance with other popular approaches, including Citrix MetaFrame, Microsoft Terminal Services, SunRay, VNC, and X. Our experimental results on web and video applications demonstrate that THINC can be as much as five times faster than traditional thin-client systems in high latency network environments and is capable of playing full-screen video at full frame rate
The Effect of Multiple Cooling Channels on the Formation of Dark Compact Objects
A dissipative dark sector can result in the formation of compact objects with
masses comparable to stars and planets. In this work, we investigate the
formation of such compact objects from a subdominant inelastic dark matter
model, and study the resulting distributions of these objects. In particular,
we consider cooling from dark Bremsstrahlung and a rapid decay process that
occurs after inelastic upscattering. Inelastic transitions introduce an
additional radiative processes which can impact the formation of compact
objects via multiple cooling channels. We find that having multiple cooling
processes changes the mass and abundance of compact objects formed, as compared
to a scenario with only one cooling channel. The resulting distribution of
these astrophysical compact objects and their properties can be used to further
constrain and differentiate between dark sectors.Comment: 20 pages, 4 figure
Angular Momentum in Giant Molecular Clouds. II. M33
We present an analysis comparing the properties of 45 giant molecular clouds
(GMCs) in M33 and the atomic hydrogen (HI) with which they are associated.
High-resolution VLA observations are used to measure the properties of HI in
the vicinity of GMCs and in regions where GMCs have not been detected. The
majority of molecular clouds coincide with a local peak in the surface density
of atomic gas, though 7% of GMCs in the sample are not associated with
high-surface density atomic gas. The mean HI surface density in the vicinity of
GMCs is 10 M_sol/pc^2 and tends to increase with GMC mass as Sigma_HI ~
M_GMC^0.27. 39 of the 45 HI regions surrounding GMCs have linear velocity
gradients of ~0.05 km/s/pc. If the linear gradients previously observed in the
GMCs result from rotation, then 53% are counterrotating with respect to the
local HI. If the linear gradients in these local HI regions are also from
rotation, 62% are counterrotating with respect to the galaxy. If magnetic
braking reduced the angular momentum of GMCs early in their evolution, the
angular velocity of GMCs would be roughly one order of magnitude lower than
what is observed. Based on our observations, we consider the possibility that
GMCs may not be rotating. Atomic gas not associated with GMCs has gradients
closer to 0.03 km/s/pc, suggesting that events occur during the course of GMC
evolution that may increase the shear in the atomic gas.Comment: Accepted for Publication in Ap
Making the Move: Migrating the Boston College Law School Library
Moving an institutional repository is no small feat. There are costs and benefits to every platform and to the migration process itself. However, Boston College Law Library\u27s partnership with Ubiquity Press has shown that this process can be approachable and create opportunities for improvement and growth of the repository. Members of the Boston College Law Library team will describe our decision process behind making the choice to move and selecting our new platform, outline the migration process itself, and discuss some of the changes that were enabled by this move to improve and modernize our repository
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