3,447 research outputs found
Large Oligomeric Complex Structures Can Be Computationally Assembled by Efficiently Combining Docked Interfaces
Macromolecular oligomeric assemblies are involved in many biochemical processes of living organisms. The benefits of such assemblies in crowded cellular environments include increased reaction rates, efficient feedback regulation, cooperativity and protective functions. However, an atomâlevel structural determination of large assemblies is challenging due to the size of the complex and the difference in binding affinities of the involved proteins. In this study, we propose a novel combinatorial greedy algorithm for assembling large oligomeric complexes from information on the approximate position of interaction interfaces of pairs of monomers in the complex. Prior information on complex symmetry is not required but rather the symmetry is inferred during assembly. We implement an efficient geometric score, the transformation match score, that bypasses the model ranking problems of stateâofâtheâart scoring functions by scoring the similarity between the inferred dimers of the same monomer simultaneously with different binding partners in a (sub)complex with a set of pregenerated docking poses. We compiled a diverse benchmark set of 308 homo and heteromeric complexes containing 6 to 60 monomers. To explore the applicability of the method, we considered 48 sets of parameters and selected those three sets of parameters, for which the algorithm can correctly reconstruct the maximum number, namely 252 complexes (81.8%) in, at least one of the respective three runs. The crossvalidation coverage, that is, the mean fraction of correctly reconstructed benchmark complexes during crossvalidation, was 78.1%, which demonstrates the ability of the presented method to correctly reconstruct topology of a large variety of biological complexes. Proteins 2015; 83:1887â1899. © 2015 The Authors. Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc
The 400d Galaxy Cluster Survey Weak Lensing Programme: I: MMT/Megacam Analysis of CL0030+2618 at z=0.50
The mass function of galaxy clusters at high redshifts is a particularly
useful probe to learn about the history of structure formation and constrain
cosmological parameters. We aim at deriving reliable masses for a
high-redshift, high-luminosity sample of clusters of galaxies selected from the
400d survey of X-ray selected clusters. Here, we will focus on a particular
object, CL0030+2618 at z=0.50 Using deep imaging in three passbands with the
MEGACAM instrument at MMT, we show that MEGACAM is well-suited for measuring
gravitational shear. We detect the weak lensing signal of CL0030+2618 at 5.8
sigma significance, using the aperture mass technique. Furthermore, we find
significant tangential alignment of galaxies out to ~10 arcmin or >2r_200
distance from the cluster centre. The weak lensing centre of CL0030+2618 agrees
with several X-ray measurements and the position of the brightest cluster
galaxy. Finally, we infer a weak lensing virial mass of M_200=7.5 10^{14} M_sun
for CL0030+2618. Despite complications by a tentative foreground galaxy group
in the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are
in remarkable agreement. This study paves the way for the largest weak lensing
survey of high-redshift galaxy clusters to date.Comment: 32 pages, 24 figures, submitted to Astronomy & Astrophysics; fixed
some LaTeX issues, now 30 pages v3: Improved version accepted by Astronomy &
Astrophysic
Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data
Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° â 0° â 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100â200âpc at a typical distance of 6âkpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4â857âGHz) in combination with low-frequency radio data at 0.408â2.3âGHz plus WMAP data at 23â94âGHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20â40âGHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4âGHz emission in the longitude range l = 300° â 0° â 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100âGHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM â 100âpc. The narrow synchrotron component has a low-frequency brightness spectral index ÎČ_(synch) â â2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150âpc in 3 Ă 10^5âyr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of T_(dust) = 20.4 ± 0.4âK, ÎČ_(FIR) = 1.94 ± 0.03 (> 353âGHz), and ÎČ_(mm) = 1.67 ± 0.02 (< 353âGHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy
3D Cosmic Shear: Cosmology from CFHTLenS
This paper presents the first application of 3D cosmic shear to a wide-field
weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing
in three dimensions using a spherical harmonic approach, and does not bin data
in the redshift direction. This is applied to CFHTLenS, a 154 square degree
imaging survey with a median redshift of 0.7 and an effective number density of
11 galaxies per square arcminute usable for weak lensing. To account for survey
masks we apply a 3D pseudo-Cl approach on weak lensing data, and to avoid
uncertainties in the highly non-linear regime, we separately analyse radial
wave numbers k<=1.5h/Mpc and k<=5.0h/Mpc, and angular wavenumbers l~400-5000.
We show how one can recover 2D and tomographic power spectra from the full 3D
cosmic shear power spectra and present a measurement of the 2D cosmic shear
power spectrum, and measurements of a set of 2-bin and 6-bin cosmic shear
tomographic power spectra; in doing so we find that using the 3D power in the
calculation of such 2D and tomographic power spectra from data naturally
accounts for a minimum scale in the matter power spectrum. We use 3D cosmic
shear to constrain cosmologies with parameters OmegaM, OmegaB, sigma8, h, ns,
w0, wa. For a non-evolving dark energy equation of state, and assuming a flat
cosmology, lensing combined with WMAP7 results in h=0.78+/-0.12,
OmegaM=0.252+/-0.079, sigma8=0.88+/-0.23 and w=-1.16+/-0.38 using only scales
k<=1.5h/Mpc. We also present results of lensing combined with first year Planck
results, where we find no tension with the results from this analysis, but we
also find no significant improvement over the Planck results alone. We find
evidence of a suppression of power compared to LCDM on small scales 1.5 < k <
5.0 h/Mpc in the lensing data, which is consistent with predictions of the
effect of baryonic feedback on the matter power spectrum.Comment: Full journal article here
http://mnras.oxfordjournals.org/content/442/2/1326.full.pdf+htm
Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B
The results of five years of development of the inner tracking system of the
HERA-B experiment and first experience from the data taking period of the year
2000 are reported. The system contains 184 chambers, covering a sensitive area
of about 20 * 20 cm2 each. The detector is based on microstrip gas counters
(MSGCs) with diamond like coated (DLC) glass wafers and gas electron
multipliers (GEMs). The main problems in the development phase were gas
discharges in intense hadron beams and aging in a high radiation dose
environment. The observation of gas discharges which damage the electrode
structure of the MSGC led to the addition of the GEM as a first amplification
step. Spurious sparking at the GEM cannot be avoided completely. It does not
affect the GEM itself but can produce secondary damage of the MSGC if the
electric field between the GEM and the MSGC is above a threshold depending on
operation conditions. We observed that aging does not only depend on the dose
but also on the spot size of the irradiated area. Ar-DME mixtures had to be
abandoned whereas a mixture of 70% Ar and 30% CO2 showed no serious aging
effects up to about 40 mC/cm deposited charge on the anodes. X-ray measurements
indicate that the DLC of the MSGC is deteriorated by the gas amplification
process. As a consequence, long term gain variations are expected. The Inner
Tracker has successfully participated in the data taking at HERA-B during
summer 2000.Comment: 29 pages, 22 figure
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