The charge ratio, R sub(mu)=N sub(mu+)/N sub(mu-), for cosmogenic multiple-muon events observed at an underground depth of 2070 mwe has been measured using the magnetized MINOS Far Detector. The ...multiple-muon events, recorded nearly continuously from August 2003 until April 2012, comprise two independent data sets imaged with opposite magnetic field polarities, the comparison of which allows the systematic uncertainties of the measurement to be minimized. The multiple-muon charge ratio is determined to be (ProQuest: Formulae and/or non-USASCII text omitted). This measurement complements previous determinations of single-muon and multiple-muon charge ratios at underground sites and serves to constrain models of cosmic-ray interactions at TeV energies.
Characterization of Proexosite I on Prothrombin Anderson, Patricia J.; Nesset, Anna; Dharmawardana, Kumudini R. ...
The Journal of biological chemistry,
06/2000, Letnik:
275, Številka:
22
Journal Article
Recenzirano
Odprti dostop
Activation of prothrombin by factor Xa is accompanied by expression of regulatory exosites I and II on the blood coagulation proteinase, thrombin. Quantitative affinity chromatography and equilibrium ...binding studies with a fluorescein-labeled derivative of the exosite I-specific peptide ligand, hirudin54–65 (5FHir54–65(SO3−), were employed to identify and characterize this site on human and bovine prothrombin and its expression on thrombin. 5FHir54–65(SO3−) showed distinctive fluorescence excitation spectral differences in complexes with prothrombin and thrombin and bound to human prothrombin and thrombin with dissociation constants of 3.2 ± 0.3 μm and 25 ± 2 nm, respectively, demonstrating a 130-fold increase in affinity for the active proteinase. The bovine proteins similarly showed a 150-fold higher affinity of 5FHir54–65(SO3−) for thrombin compared with prothrombin, despite a 2–5-fold lower affinity of the peptides for the bovine proteins. Unlabeled, Tyr63-sulfated and nonsulfated hirudin peptides bound competitively with 5FHir54–65(SO3−) to human and bovine prothrombin and thrombin, exhibiting similar, 40–70-fold higher affinities for the proteinases, although nonsulfated Hir54–65 bound with 7–17-fold lower affinity than the sulfated analog. These studies characterize proexosite I for the first time as a specific binding site for hirudin peptides on both human and bovine prothrombin that is present in a conformationally distinct, low affinity state and is activated with a ∼100-fold increase in affinity when thrombin is formed.
In an essential step of blood coagulation, factor V is proteolytically processed by thrombin to generate the activated protein cofactor, factor Va, and to release the activation fragments E and C1. ...For the identification and characterization of sites of thrombin binding to factor V and its activation products, a new method was developed for immobilizing thrombin and other serine proteinases specifically (≥92%) through their active sites and used in affinity chromatography studies of the interactions. Interactions of factor V with exosite I of thrombin were shown to regulate the factor V activation pathway from the 93% ± 12% inhibition of the rate of activation correlated with specific binding of hirudin54-65 to this exosite. Chromatography of factor V on active-site-immobilized thrombin showed only a weak interaction, while the factor Va heterodimer bound specifically and with apparently higher affinity, in an interaction that was prevented by hirudin54-65. The heavy chain of subunit-dissociated factor Va bound to immobilized thrombin, while the light-chain subunit and fragment E had no detectable affinity. These results demonstrate a previously undescribed, exosite I-dependent interaction of thrombin with factor Va that occurs through the factor Va heavy chain. They support the further conclusion that similar exosite I-dependent binding of thrombin to the heavy-chain region of factor V contributes to recognition of factor V as a specific thrombin substrate and thereby regulates proteolytic activation of the protein cofactor.
We have developed a near-infrared spectrometer designed to measure the absolute intensity of the solar 854.2 nm Ca II Fraunhofer line, scattered by interplanetary dust, in the zodiacal light (ZL) ...spectrum. Based on the known equivalent line width in the solar spectrum, this measurement can derive the zodiacal brightness, testing models of the ZL based on morphology that are used to determine the extragalactic background light in absolute photometry measurements. The spectrometer is based on a simple high-resolution tipped filter placed in front of a compact camera with wide-field refractive optics to provide the large optical throughput and high sensitivity required for rocket-borne observations. We discuss the instrument requirements for an accurate measurement of the absolute ZL brightness, the measured laboratory characterization, and the instrument performance in flight.
Motivated by the prediction of a high TeV luminosity we investigated whether the blazar 1ES 1727+502 (z = 0.055) is emitting very high energy (VHE, E > 100 GeV) γ rays. We observed the BL Lac object ...1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes for 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 h. To study the multiwavelength spectral energy distribution (SED), we used simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations from instruments UVOT and XRT on board of the Swift satellite, and high energy (HE, 0.1 GeV–100 GeV) γ-ray data from the Fermi-LAT instrument. We detected, for the first time, VHE γ-ray emission from 1ES 1727+502 at a statistical significance of 5.5σ. The integral flux above 150 GeV is estimated to be (2.1 ± 0.4)% of the Crab nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7 ± 0.5). No significant short-term variability was found in any of the wavebands presented here. We model the SED using a one-zone synchrotron self-Compton model obtaining parameters typical for this class of sources.
Context. We present the results of a long M 87 monitoring campaign in very high energy γ-rays with the MAGIC-I Cherenkov telescope. Aims. We aim to model the persistent non-thermal jet emission by ...monitoring and characterizing the very high energy γ-ray emission of M 87 during a low state. Methods. A total of 150 h of data were taken between 2005 and 2007 with the single MAGIC-I telescope, out of which 128.6 h survived the data quality selection. We also collected data in the X-ray and Fermi-LAT bands from the literature (partially contemporaneous). Results. No flaring activity was found during the campaign. The source was found to be in a persistent low-emission state, which was at a confidence level of 7σ. We present the spectrum between 100 GeV and 2 TeV, which is consistent with a simple power law with a photon index Γ = 2.21 ± 0.21 and a flux normalization at 300 GeV of (7.7 ± 1.3) × 10-8 TeV-1 s-1 m-2. The extrapolation of the MAGIC spectrum into the GeV energy range matches the previously published Fermi-LAT spectrum well, covering a combined energy range of four orders of magnitude with the same spectral index. We model the broad band energy spectrum with a spine layer model, which can satisfactorily describe our data.
The grammatical relations of NPs in sentences are ordered in a hierarchy that is reflected in a wide array of linguistic phenomena. It is hypothesized that this hierarchy is related to the conceptual ...accessibility of the intended referents of NPs that commonly occur in particular relational roles, with relations higher in the hierarchy typically occupied by NPs representing more accessible concepts. An experiment (N = 64) on the formulation of sentences examined the relationship between conceptual accessibility & grammatical relations for 3 levels in the hierarchy: the subject, direct O, & indirect O. There was a strong & systematic influence of conceptual accessibility on the surface syntactic structure of sentences. The attribution of this effect to grammatical role assignments, rather than to serial ordering mechanisms, was supported by the absence of an effect of conceptual accessibility on the order of Ns in conjunctive NPs. This pattern of results can be explained within current theories of sentence production. 3 Tables, 1 Figure, 52 References. HA
The blood coagulation proteinase, thrombin, converts factor V into factor Va through a multistep activation pathway that is regulated by interactions with thrombin exosites. Thrombin exosite ...interactions with human factor V and its activation products were quantitatively characterized in equilibrium binding studies based on fluorescence changes of thrombin covalently labeled with 2-anilinonaphthalene-6-sulfonic acid (ANS) linked to the catalytic site histidine residue by Nalpha-(acetylthio)acetyl-D-Phe-Pro-Arg-CH2Cl (ANSFPR-thrombin). Exosite I was shown to play a predominant role in the binding of factor V and factor Va from the effect of the exosite I-specific ligand, hirudin54-65, on the interactions. Factor V and factor Va bound to exosite I of ANSFPR-thrombin with similar dissociation constants of 3.4 +/- 1.3 and 1.1 +/- 0.4 microM and fluorescence enhancements of 182 +/- 41 and 127 +/- 17%, respectively. Native thrombin and labeled thrombin bound with similar affinity to factor Va. Among factor V activation products, the factor Va heavy chain was shown to contain the site of exosite I binding, whereas exosite I-independent, lower affinity interactions were observed for activation fragments E and C1, and no detectable binding was observed for the factor Va light chain. The results support the conclusion that the factor V activation pathway is initiated by exosite I-mediated binding of thrombin to a site in the heavy chain region of factor V that facilitates the initial cleavage at Arg709 to generate the heavy chain of factor Va. The results further suggest that binding of thrombin through exosite I to factor V activation intermediates may regulate their conversion to factor Va and that similar binding of thrombin to the factor Va produced may reflect a mode of interaction involved in the regulation of prothrombin activation.
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