Remote sensing of volcanic CO2, HF, HCl, SO2, and BrO in the downwind plume of Mt. Etna

Remote sensing of the gaseous composition of non-eruptive, passively degassing volcanic plumes can be a tool to gain insight into volcano interior processes. Here, we report on a field study in September 2015 that demonstrates the feasibility of remotely measuring the volcanic enhancements of carbon dioxide (CO2), hydrogen fluoride (HF), hydrogen chloride (HCl), sulfur dioxide (SO2), and bromine monoxide (BrO) in the downwind plume of Mt. Etna using portable and rugged spectroscopic instrumentation. To this end, we operated the Fourier transform spectrometer EM27/SUN for the shortwave-infrared (SWIR) spectral range together with a co-mounted UV spectrometer on a mobile platform in direct-sun view at 5 to 10 km distance from the summit craters. The 3 days reported here cover several plume traverses and a sunrise measurement. For all days, intra-plume HF, HCl, SO2, and BrO vertical column densities (VCDs) were reliably measured exceeding 5 x 10(16), 2 x 10(17), 5 x 10(17), and 1 x 10(14) molec cm(2), with an estimated precision of 2.2 x 10(15), 1.3 x 10(16), 3.6 x 10(16), and 1.3 x 10(13) molec cm(2), respectively. Given that CO2, unlike the other measured gases, has a large and wellmixed atmospheric background, derivation of volcanic CO2 VCD enhancements (Delta CO2) required compensating for changes in altitude of the observing platform and for background concentration variability. The first challenge was met by simultaneously measuring the overhead oxygen (O-2) columns and assuming covariation of O-2 and CO2 with altitude. The atmospheric CO2 background was found by identifying background soundings via the coemitted volcanic gases. The inferred Delta CO2 occasionally exceeded 2 x 10(19) molec cm(-2) with an estimated precision of 3.7 x 10(18) molec cm(-2) given typical atmospheric background VCDs of 7 to 8 x 10(21) molec cm(-2). While the correlations of Delta CO2 with the other measured volcanic gases confirm the detection of volcanic CO2 enhancements, correlations were found of variable significance (R-2 ranging between 0.88 and 0.00). The intra-plume VCD ratios Delta CO2/SO2, SO2/HF, SO2/HCl, and SO2/BrO were in the range 7.1 to 35.4, 5.02 to 21.2, 1.54 to 3.43, and 2.9 x 10(3) to 12.5 x 10(3), respectively, showing pronounced day-to-day and intra-day variability

Local anaesthetic blockade of neuronal nicotinic ACh receptor-channels in rat parasympathetic ganglion cells.

1 The effects of the local anaesthetics QX-222 and procaine on nicotinic acetylcholine (ACh)-evoked currents in cultured parasympathetic cardiac neurones of the rat were investigated by use of the whole-cell, perforated-patch, and outside-out recording configurations of the patch clamp method. 2 QX-222 and procaine, applied to the extracellular surface, reversibly inhibited the peak amplitude of the whole-cell nicotinic ACh-evoked current in a concentration-dependent manner, with half-maximal inhibitory concentrations (IC50) of 28 microM and 2.8 microM, respectively, at -80 mV. In these neurones, the sustained inward current mediated by M1 muscarinic receptor activation was unaltered by QX-222, and neither local anaesthetic affected the adenosine 5'-triphosphate (ATP)-evoked current. 3 QX-222 and procaine block of nicotinic ACh-evoked inward current was voltage-dependent and enhanced by hyperpolarization. An e-fold change in their dissociation equilibrium constants (Kd) resulted from a 62 mV and a 122 mV change in membrane potential, respectively. 4 Both local anaesthetics produce a concentration-dependent increase in the half-time of decay of the nicotinic ACh-evoked inward current. 5 Measurements of unitary currents in outside-out patches showed that QX-222 reversibly increased the mean burst duration and closed time and reduced the mean channel open time and open-state probability of the nicotinic ACh receptor-channel (AChR) in a concentration-dependent manner. 6 The Kd and voltage sensitivity of local anaesthetic block of the nicotinic AChR in rat intracardiac neurones suggests that the pore-forming region of this channel differs from that of the AChR in frog and rat skeletal muscle and from the neuronal alpha 4 beta 2 ACh receptor-channel

Structural insights into the dynamics and function of the C-terminus of the E. coli RNA chaperone Hfq

The hexameric Escherichia coli RNA chaperone Hfq (Hfq(Ec)) is involved in riboregulation of target mRNAs by small trans-encoded RNAs. Hfq proteins of different bacteria comprise an evolutionarily conserved core, whereas the C-terminus is variable in length. Although the structure of the conserved core has been elucidated for several Hfq proteins, no structural information has yet been obtained for the C-terminus. Using bioinformatics, nuclear magnetic resonance spectroscopy, synchrotron radiation circular dichroism (SRCD) spectroscopy and small angle X-ray scattering we provide for the first time insights into the conformation and dynamic properties of the C-terminal extension of Hfq(Ec). These studies indicate that the C-termini are flexible and extend laterally away from the hexameric core, displaying in this way features typical of intrinsically disordered proteins that facilitate intermolecular interactions. We identified a minimal, intrinsically disordered region of the C-terminus supporting the interactions with longer RNA fragments. This minimal region together with rest of the C-terminal extension provides a flexible moiety capable of tethering long and structurally diverse RNA molecules. Furthermore, SRCD spectroscopy supported the hypothesis that RNA fragments exceeding a certain length interact with the C-termini of Hfq(Ec)