160 research outputs found

    Interaction of Human Serum Albumin with short Polyelectrolytes: A study by Calorimetry and Computer Simulation

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    We present a comprehensive study of the interaction of human serum albumin (HSA) with poly(acrylic acid) (PAA; number average degree of polymerization: 25) in aqueous solution. The interaction of HSA with PAA is studied in dilute solution as the function of the concentration of added salt (20 - 100 mM) and temperature (25 - 37^{\circ}C). Isothermal titration calorimetry (ITC) is used to analyze the interaction and to determine the binding constant and related thermodynamic data. It is found that only one PAA chain is bound per HSA molecule. The free energy of binding ΔGb\Delta G_b increases with temperature significantly. ΔGb\Delta G_b decreases with increasing salt concentration and is dominated by entropic contributions due to the release of bound counterions. Coarse-grained Langevin computer simulations treating the counterions in an explicit manner are used study the process of binding in detail. These simulations demonstrate that the PAA chains are bound in the Sudlow II site of the HSA. Moreover, ΔGb\Delta G_b is calculated from the simulations and found to be in very good agreement with the measured data. The simulations demonstrate clearly that the driving force of binding is the release of counterions in full agreement with the ITC-data

    Electronic excitations stabilized by a degenerate electron gas in semiconductors

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    Excitons in semiconductors and insulators consist of fermionic subsystems, electrons and holes, whose attractive interaction facilitates bound quasiparticles with quasi-bosonic character. In the presence of a degenerate electron gas, such excitons dissociate due to free carrier screening. Despite their absence, we found pronounced emission traces in the below-band-edge region of bulk, germanium-doped GaN up to a temperature of 100 K, mimicking sharp spectral features at high free electron concentrations (3.4E19–8.9E19 cm−3). Our interpretation of the data suggests that a degenerate, three-dimensional electron gas stabilizes a novel class of quasiparticles, which we name collexons. These many-particle complexes are formed by exchange of electrons with the Fermi gas. The potential observation of collexons and their stabilization with rising doping concentration is enabled by high crystal quality due to the almost ideal substitution of host atoms with dopants.DFG, 43659573, SFB 787: Semiconductor Nanophotonics: Materials, Models, Device

    NieKom - Eine neue Datenbasis für die kommunale Wahl- und Policyforschung in Niedersachsen

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    Die Verfügbarkeit kommunaler Wahldaten stellt im bundesdeutschen Kontext häufig noch eine Hürde für die empirische Wahl- und Policyforschung dar. Der in diesem Beitrag vorgestellte "NieKom"-Datensatz, bestehend aus einem scientific use file (https://uol.de/polsys/niekom) und einer Online-Informationsplattform (http://niekom.uni-oldenburg.de/), möchte dazu beitragen, die kommunale Wahl- und Policyforschung für das Bundesland Niedersachsen auf eine breitere empirische Basis zu stellen und darüber hinaus ein Online-Informationsangebot für die politisch interessierte Öffentlichkeit zu bieten. "NieKom" ist ein Multi-Panel-Datensatz, in dem erstmalig als Vollerhebung alle Wahlergebnisse aus den niedersächsischen Kommunen für alle relevanten Wahltypen (Gemeinde-, Kreis-, Europa-, Landtags- und Bundestagswahlen) im Zeitraum von 1974 bis 2017 abgebildet sind.In the German context, the availability of municipal election data often represents a hurdle for empirical electoral and policy research. The "NieKom" dataset presented in this article, consisting of a scientific use file (https://uol.de/polsys/niekom) and an online information platform (http://niekom.uni-oldenburg.de/), aims to contribute to placing municipal electoral and policy research on Lower Saxony on a broader empirical basis and also offers an online information board for the politically interested public. "NieKom" is a multi-panel dataset which includes, for the first time, all election results from Lower Saxony's municipalities for all relevant types of elections (municipal, district, European, state and federal elections) in the period from 1974 to 2017

    Mass-spectrometric identification of a novel angiotensin peptide in human plasma

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    Objective— Angiotensin peptides play a central role in cardiovascular physiology and pathology. Among these peptides, angiotensin II (Ang II) has been investigated most intensively. However, further angiotensin peptides such as Ang 1-7, Ang III, and Ang IV also contribute to vascular regulation, and may elicit additional, different, or even opposite effects to Ang II. Here, we describe a novel Ang II-related, strong vasoconstrictive substance in plasma from healthy humans and end-stage renal failure patients. Methods and Results— Chromatographic purification and structural analysis by matrix-assisted laser desorption/ionisation time-of-flight/time-of-flight (MALDI-TOF/TOF) revealed an angiotensin octapeptide with the sequence Ala-Arg-Val-Tyr-Ile-His-Pro-Phe, which differs from Ang II in Ala1 instead of Asp1. Des[Asp1]-[Ala1]-Ang II, in the following named Angiotensin A (Ang A), is most likely generated enzymatically. In the presence of mononuclear leukocytes, Ang II is converted to Ang A by decarboxylation of Asp1. Ang A has the same affinity to the AT1 receptor as Ang II, but a higher affinity to the AT2 receptor. In the isolated perfused rat kidney, Ang A revealed a smaller vasoconstrictive effect than Ang II, which was not modified in the presence of the AT2 receptor antagonist PD 123319, suggesting a lower intrinsic activity at the AT1 receptor. Ang II and Ang A concentrations in plasma of healthy subjects and end-stage renal failure patients were determined by matrix-assisted laser desorption/ionisation mass-analysis, because conventional enzyme immunoassay for Ang II quantification did not distinguish between Ang II and Ang A. In healthy subjects, Ang A concentrations were less than 20% of the Ang II concentrations, but the ratio Ang A / Ang II was higher in end-stage renal failure patients. Conclusion— Ang A is a novel human strong vasoconstrictive angiotensin-derived peptide, most likely generated by enzymatic transformation through mononuclear leukocyte-derived aspartate decarboxylase. Plasma Ang A concentration is increased in end-stage renal failure. Because of its stronger agonism at the AT2 receptor, Ang A may modulate the harmful effects of Ang II. In this study, a new angiotensin-peptide of human plasma is described, which is characterized as a strong AT2-receptor agonist

    The correlation between reading and mathematics ability at age twelve has a substantial genetic component

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    Dissecting how genetic and environmental influences impact on learning is helpful for maximizing numeracy and literacy. Here we show, using twin and genome-wide analysis, that there is a substantial genetic component to children’s ability in reading and mathematics, and estimate that around one half of the observed correlation in these traits is due to shared genetic effects (so-called Generalist Genes). Thus, our results highlight the potential role of the learning environment in contributing to differences in a child’s cognitive abilities at age twelve

    Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke

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    Genetic factors have been implicated in stroke risk but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) in ischemic stroke and its subtypes in 3,548 cases and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 cases and 6,281 controls. We replicated reported associations between variants close to PITX2 and ZFHX3 with cardioembolic stroke, and a 9p21 locus with large vessel stroke. We identified a novel association for a SNP within the histone deacetylase 9(HDAC9) gene on chromosome 7p21.1 which was associated with large vessel stroke including additional replication in a further 735 cases and 28583 controls (rs11984041, combined P = 1.87×10−11, OR=1.42 (95% CI) 1.28-1.57). All four loci exhibit evidence for heterogeneity of effect across the stroke subtypes, with some, and possibly all, affecting risk for only one subtype. This suggests differing genetic architectures for different stroke subtypes

    AARC: First draft of the Blueprint Architecture for Authentication and Authorisation Infrastructures

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    AARC (Authentication and Authorisation for Research Communities) is a two-year EC-funded project to develop and pilot an integrated cross-discipline authentication and authorisation framework, building on existing authentication and authorisation infrastructures (AAIs) and production federated infrastructure. AARC also champions federated access and offers tailored training to complement the actions needed to test AARC results and to promote AARC outcomes. This article describes a high-level blueprint architectures for interoperable AAIs
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