3,389 research outputs found
The Third Dimension of Reading the Sugar Code by Lectins
Coding of biological information is not confined to nucleic acids and proteins. Endowed with the highest level of structural versatility among biomolecules, the glycan chains of cellular glycoconjugates are well-suited to generate molecular messages/signals in a minimum of space. The sequence and shape of oligosaccharides as well as spatial aspects of multivalent presentation are assumed to underlie the natural specificity/selectivity that cellular glycans have for endogenous lectins. In order to eventually unravel structure-activity profiles cyclic scaffolds have been used as platforms to produce glycoclusters and afford valuable tools. Using adhesion/growth-regulatory galectins and the pan-galectin ligand lactose as a model, emerging insights into the potential of cyclodextrins, cyclic peptides, calixarenes and glycophanes for this purpose are presented herein. The systematic testing of lectin panels with spatially defined ligand presentations can be considered as a biomimetic means to help clarify the mechanisms, which lead to the exquisite accuracy at which endogenous lectins select their physiological counterreceptors from the complexity of the cellular glycome
Black hole relics in large extra dimensions
Recent calculations applying statistical mechanics indicate that in a setting with compactified large extra dimensions a black hole might evolve into a (quasi-)stable state with mass close to the new fundamental scale M f. Black holes and therefore their relics might be produced at the LHC in the case of extra-dimensional topologies. In this energy regime, Hawking's evaporation scenario is modified due to energy conservation and quantum effects. We reanalyse the evaporation of small black holes including the quantisation of the emitted radiation due to the finite surface of the black hole. It is found that observable stable black hole relics with masses sim 1-3 M f would form which could be identified by a delayed single jet with a corresponding hard momentum kick to the relic and by ionisation, e.g. in a TPC
Dietary Intake of Natural Sources of Docosahexaenoic Acid and Folate in Pregnant Women of Three European Cohorts
Background: Folic acid plays a fundamental role in cell division and differentiation. Docosahexaenoic acid (DHA) has been associated with infantile neurological and cognitive development. Thus, optimal intrauterine development and growth requires adequate supply of these nutrients during pregnancy. Methods: Healthy pregnant women, aged 18-41 years, were recruited in Granada (Spain; n = 62), Munich (Germany; n = 97) and Pecs (Hungary; n = 152). We estimated dietary DHA and folate intake in weeks 20 (w20) and 30 of gestation (w30) using a food frequency questionnaire with specific focus on the dietary sources of folate and DHA. Results: Both w20 and w30 Spanish participants had significantly higher daily DHA intakes (155 +/- 13 and 161 +/- 9 mg/1,000 kcal) than the German (119 +/- 9 and 124 +/- 12 mg/1,000 kcal; p = 0.002) and Hungarian participants (122 +/- 8 and 125 +/- 10 mg/1,000 kcal; p = 0.005). Hungarian women had higher folate intakes in w20 and w30 (149 +/- 5 and 147 +/- 6 mu g/1,000 kcal) than Spanish (112 +/- 2 and 110 +/- 2 mu g/1,000 kcal; p < 0.001) and German participants (126 +/- 4 and 120 +/- 6 mu g/1,000 kcal; p < 0.001), respectively. Conclusion: Dietary DHA and folate intake of pregnant women differs significantly across the three European cohorts. Only 7% of the participants reached the recommended folate intake during pregnancy, whereas nearly 90% reached the DHA recommended intake of 200 mg per day. Copyright (C) 2008 S. Karger AG, Base
Interplay of electromagnetic noise and Kondo effect in quantum dots
We investigate the influence of an electromagnetic environment, characterized
by a finite impedance , on the Kondo effect in quantum dots. The
circuit voltage fluctuations couple to charge fluctuations in the dot and
influence the spin exchange processes transferring charge between the
electrodes. We discuss how the low-energy properties of a Kondo quantum dot
subject to dynamical Coulomb blockade resemble those of Kondo impurities in
Luttinger liquids. Using previous knowledge based on the bosonization of
quantum impurity models, we show that low-voltage conductance anomalies appear
at zero temperature. The conductance can vanish at low temperatures even in
presence of a screened impurity spin. Moreover, the quantitative determination
of the corresponding Kondo temperature depends on the full frequency-dependent
impedance of the circuit. This is demonstrated by a weak-coupling calculation
in the Kondo interaction, taking into account the full distribution of
excited environmental modes.Comment: 10 pages, 4 figures, revised version, new titl
Modeling quark-hadron duality in polarization observables
We apply a model for the study of quark-hadron duality in inclusive electron
scattering to the calculation of spin observables. The model is based on
solving the Dirac equation numerically for a scalar confining linear potential
and a vector color Coulomb potential. We qualitatively reproduce the features
of quark-hadron duality for all potentials considered, and discuss the onset of
scaling and duality for the responses, spin structure functions, and
polarization asymmetries. Duality may be applied to gain access to kinematic
regions which are hard to access in deep inelastic scattering, namely for
, and we discuss which observables are most suitable for this
application of duality
Open star clusters in the Milky Way - Comparison of photometric and trigonometric distance scales based on Gaia TGAS data
The global survey of star clusters in the Milky Way (MWSC) is a comprehensive
list of 3061 objects that provides, among other parameters, distances to
clusters based on isochrone fitting. The Tycho-Gaia Astrometric Solution (TGAS)
catalogue, which is a part of Gaia data release 1 (Gaia DR1), delivers accurate
trigonometric parallax measurements for more than 2 million stars, including
those in star clusters. We compare the open cluster photometric distance scale
with the measurements given by the trigonometric parallaxes from TGAS to
evaluate the consistency between these values. The average parallaxes of
probable cluster members available in TGAS provide the trigonometric distance
scale of open clusters, while the photometric scale is given by the distances
published in the MWSC. Sixty-four clusters are suited for comparison as they
have more than 16 probable members with parallax measurements in TGAS. We
computed the average parallaxes of the probable members and compared these to
the photometric parallaxes derived within the MWSC. We find a good agreement
between the trigonometric TGAS-based and the photometric MWSC-based distance
scales of open clusters, which for distances less than 2.3 kpc coincide at a
level of about 0.1 mas with no dependence on the distance. If at all, there is
a slight systematic offset along the Galactic equator between and
galactic longitude.Comment: Accepted for publication as a Letter in Astronomy and Astrophysics, 4
pages, 4 figure
KEGG spider: interpretation of genomics data in the context of the global gene metabolic network
KEGG spider is a web-based tool for interpretation of experimentally derived gene lists in order to gain understanding of metabolism variations at a genomic level. KEGG spider implements a 'pathway-free' framework that overcomes a major bottleneck of enrichment analyses: it provides global models uniting genes from different metabolic pathways. Analyzing a number of experimentally derived gene lists, we demonstrate that KEGG spider provides deeper insights into metabolism variations in comparison to existing methods
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