GTP-dependent Ca2+ release from rat liver microsomes Vesicle fusion is not required

AbstractThe GTP-dependent calcium release from rat liver microsomes is known to be promoted in the presence of colloids like polyethyleneglycol (PEG), polyvinylpyrrolidine, or albumin. Dawson et al. [(1987) Biochem. J. 244, 87–92] using the ‘fusogen’ PEG have concluded that both GTP-induced calcium efflux and the enhancement of InsP3-promoted calcium release in the presence of GTP could be attributed to a GTP-dependent vesicle fusion. Here, using the more physiological colloid albumin we report that GTP-induced calcium release from rat liver microsomes may not be linked to vesicle fusion

The coupling of the hydrated proton to its first solvation shell

The transfer of a hydrated proton between water molecules in aqueous solution is accompanied by the large-scale structural reorganization of the environment as the proton relocates, giving rise to the Grotthus mechanism. The Zundel (H5O2+) and Eigen (H9O4+) cations are the main intermediate structures in this process. They exhibit radically different gas-phase infrared (IR) spectra, indicating fundamentally different environments of the solvated proton in its first solvation shell. The question arises: is there a least common denominator structure that explains the IR spectra of the Zundel and Eigen cations, and hence of the solvated proton? Full dimensional quantum simulations of these protonated cations demonstrate that two dynamical water molecules embedded in the static environment of the parent Eigen cation constitute this fundamental subunit. It is sufficient to explain the spectral signatures and anharmonic couplings of the solvated proton in its first solvation shell. In particular, we identify the anharmonic vibrational modes that explain the large broadening of the proton transfer peak in the experimental IR spectrum of the Eigen cation, of which the origin remained so far unclear. Our findings about the quantum mechanical structure of the first solvation shell provide a starting point for further investigations of the larger protonated water clusters with second and additional solvation shells.Comment: main article with 4 figures, methods, and supporting informatio

Kommunikation in Krisen

Das Projekt "Kommunikation in Krisen" analysiert kommunikative Prozesse in Krisen. Diese werden verstanden als eine ereignisbezogene gesellschaftliche Verunsicherung, in deren Folge sich ein temporärer, dynamischer sozialer Zusammenhang zur Bewältigung dieser Verunsicherung herausbildet. Auf der Basis von systematischen Literaturrecherchen und Gesprächen mit ausgewählten Expert*innen aus verschiedenen Akteursbereichen werden kommunikative Prozesse in der aktuell herrschenden COVID-19-Krise aufgezeigt. Um Kommunikation in Krisen systematisch zu beschreiben, wird ein figurationstheoretischer Ansatz verfolgt, der Kommunikation in Krisen als ein Interdependenzgeflecht versteht und die an der Kommunikation beteiligten Akteure, deren jeweiligen handlungsleitenden Orientierungen und kommunikativen Praktiken in den Blick nimmt. Im Zentrum stehen die bereichsspezifischen Handlungslogiken von Akteuren aus den Bereichen: Öffentliche Gesundheit und Sicherheit, Wissenschaft und Forschung, Öffentlichkeit und Journalismus, gruppenspezifische Interessen, Lebenswelt der einzelnen Mitglieder der Gesellschaft. Auf der Basis vorliegender Befunde aus der Forschung und ergänzender Expert*innengespräche werden die Wahrnehmung der Kommunikation in der Krise sowie die verschiedenen handlungsleitenden Orientierungen untersucht. Geleitet vom figurationstheoretischen Ansatz werden erstens der prozesshafte Charakter von Krisen und ihrer kommunikativen Bewältigung herausgearbeitet, zweitens die Vielfalt der an der kommunikativen Aushandlung ihrer Bewältigung beteiligten Akteure sowie drittens die Herausforderungen, die sich aus den vielfältigen rollen- und lebensweltbezogenen Ansprüchen, Erwartungen und Handlungsorientierungen ergeben. Auf dieser Grundlage werden verschiedene bereichsübergreifende Herausforderungen für die Kommunikation in Krisen identifiziert. Diese werden in Form von Spannungsfeldern beschrieben, in denen die Kommunikation in Krise verlaufen kann, etwa zwischen Konsonanz und Vielstimmigkeit, Warnung und Beruhigung, Vereinfachung und Differenzierung, Umfassende Information und Orientierungshilfe, Eigenverantwortung und Regulierung

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file