Angle-resolved, mass-selected ion spectroscopy of carbon K-shell excited CF3CCH

Total photoabsorption cross section and peak assignments were presented for CF3CCH in the carbon K-shell region. Anisotropy parameters of fragment ions obtained by means of an angle-resolved mass spectrometer were helpful to the peak assignments of the K-shell excitation into π and σ states. Kinetic energy distributions of the H+, CH+, C2H+ and CF2+ fragment ions were fitted using a Gaussian function with one peak, while those of the CF3+ fragment ion were analyzed by use of two and three components for the C K-shell excitation of the CF3 and C2H sides, respectively. The kinetic energy distribution of the CF3+ fragment ion was reasonably understood by the consideration that photofragmentation of the K-shell excited molecule probably competes with intramolecular energy relaxation in which the CF3 group works as an effective energy reservoir. The yields of the CFn+ (n = 2,3), C3FH2+ and C3F2H2+ ions were dependent on the site of excitation

Angle-resolved, mass-selected ion spectroscopy of carbon K-shell excited CF3CCH

Total photoabsorption cross section and peak assignments were presented for CF3CCH in the carbon K-shell region. Anisotropy parameters of fragment ions obtained by means of an angle-resolved mass spectrometer were helpful to the peak assignments of the K-shell excitation into π and σ states. Kinetic energy distributions of the H+, CH+, C2H+ and CF2+ fragment ions were fitted using a Gaussian function with one peak, while those of the CF3+ fragment ion were analyzed by use of two and three components for the C K-shell excitation of the CF3 and C2H sides, respectively. The kinetic energy distribution of the CF3+ fragment ion was reasonably understood by the consideration that photofragmentation of the K-shell excited molecule probably competes with intramolecular energy relaxation in which the CF3 group works as an effective energy reservoir. The yields of the CFn+ (n = 2,3), C3FH2+ and C3F2H2+ ions were dependent on the site of excitation

On the ionization energy of CF3SF5 in the valence region measured by angle-resolved photoelectron spectroscopy

Ionization energies for valence electrons of CF3SF5 were measured in the 12-35 eV region by means of angle-resolved photoelectron spectroscopy. The observed ionization energies were basically consistent with previous ones measured by threshold photoelectron and HeI photoelectron spectroscopy, and the ionization levels at 22.60, 26.92 and 27.86 eV were newly observed. Asymmetry parameter derived at hν = 684.7 eV was a constant of β = 1.02 ± 0.04 in the ionization energy lower than 20 eV, suggesting that lone pair electron of F atom is probably released through 2p → εd like electron emission. Characters of the 22 valence bands were elucidated with the help of ab initio calculations and of the nature of valence orbitals for CF4 and SF

Angle-resolved ion-yield measurements of CO2 in the O 1s to Rydberg excitation region

Angle-resolved energetic-ion-yield spectra were observed in the region of the O 1s to Rydberg excitation of CO2 with incident photon energy resolving power E/ΔE≃14 000. The assignments of the electronic states were established in accordance with the angular distribution data. All the observed vibrational structures were assigned to the antisymmetric stretching vibrations caused by the vibronic coupling between the nearly degenerate O 1s core-excited states. A Franck-Condon analysis was performed within the linear coupling model

Shake-off of loosely bound electrons in Auger decays of Kr 2p core hole states

Multicharged Kr ions have been measured using monochromatized undulator radiation combined with a coincidence technique. It has been found that a charge-state distribution of Kr ions being coincident with satellite peaks of Kr 2p3/2 photoelectron is slightly different from that for the main line. Resonant Auger peaks for 2p–1nl-->1G4 nl transitions generated essentially Kr4+ only, which differs from the charge-state distribution for the normal Auger peak. These findings suggest that loosely bound electrons in high Rydberg orbitals are easily shaken-off in electron emission processes.Erratum is added on the last page

Variation in resonant Auger yields into the 1G4•nl states of Kr across the L3 threshold

Resonant Auger transitions into 1G4•nl states following Kr 2p3/2 electron excitation have been measured using monochromatized undulator radiation and a hemispherical electron energy analyzer. A clear identification of electron peaks was made for the 1G4•5s, 1G4•4d, 1G4•5d and so forth when the photon energy approached to the ionization threshold. The formation of the 1G4•4d state was found over a relatively wide energy range across the threshold, because of the short lifetime of the 2p hole and of shake effects in electron emission processes. The angular dependence of these decays showed little effect on the polarization direction of the incident photon, which suggests that little anisotropy is related to that of the normal Auger transition into the 1G4 state

A putative relay circuit providing low-threshold mechanoreceptive input to lamina I projection neurons via vertical cells in lamina II of the rat dorsal horn

Background: Lamina I projection neurons respond to painful stimuli, and some are also activated by touch or hair movement. Neuropathic pain resulting from peripheral nerve damage is often associated with tactile allodynia (touch-evoked pain), and this may result from increased responsiveness of lamina I projection neurons to non-noxious mechanical stimuli. It is thought that polysynaptic pathways involving excitatory interneurons can transmit tactile inputs to lamina I projection neurons, but that these are normally suppressed by inhibitory interneurons. Vertical cells in lamina II provide a potential route through which tactile stimuli can activate lamina I projection neurons, since their dendrites extend into the region where tactile afferents terminate, while their axons can innervate the projection cells. The aim of this study was to determine whether vertical cell dendrites were contacted by the central terminals of low-threshold mechanoreceptive primary afferents. Results: We initially demonstrated contacts between dendritic spines of vertical cells that had been recorded in spinal cord slices and axonal boutons containing the vesicular glutamate transporter 1 (VGLUT1), which is expressed by myelinated low-threshold mechanoreceptive afferents. To confirm that the VGLUT1 boutons included primary afferents, we then examined vertical cells recorded in rats that had received injections of cholera toxin B subunit (CTb) into the sciatic nerve. We found that over half of the VGLUT1 boutons contacting the vertical cells were CTb-immunoreactive, indicating that they were of primary afferent origin. Conclusions: These results show that vertical cell dendritic spines are frequently contacted by the central terminals of myelinated low-threshold mechanoreceptive afferents. Since dendritic spines are associated with excitatory synapses, it is likely that most of these contacts were synaptic. Vertical cells in lamina II are therefore a potential route through which tactile afferents can activate lamina I projection neurons, and this pathway could play a role in tactile allodynia

Vibrational effect on the fragmentation dynamics of the C K-shell excited CF2CH2

Photoabsorption cross-sections of CF2CH2 were measured in the carbon K-edge region and linear time-of-flight mass spectra were acquired at some photon energies across the two π* peaks. The kinetic energy distributions of CH2+ and CF2+ with two components were deduced from the analysis of the mass spectra. The CH2+ ion with high kinetic energies increases with the extent of vibrational excitation of the CF 1s-1π* state, indicating that molecular vibrations play an important role in the photofragmentation of the inner-shell excited molecule

Genetic Characterization of Conserved Charged Residues in the Bacterial Flagellar Type III Export Protein FlhA

For assembly of the bacterial flagellum, most of flagellar proteins are transported to the distal end of the flagellum by the flagellar type III protein export apparatus powered by proton motive force (PMF) across the cytoplasmic membrane. FlhA is an integral membrane protein of the export apparatus and is involved in an early stage of the export process along with three soluble proteins, FliH, FliI, and FliJ, but the energy coupling mechanism remains unknown. Here, we carried out site-directed mutagenesis of eight, highly conserved charged residues in putative juxta- and trans-membrane helices of FlhA. Only Asp-208 was an essential acidic residue. Most of the FlhA substitutions were tolerated, but resulted in loss-of-function in the ΔfliH-fliI mutant background, even with the second-site flhB(P28T) mutation that increases the probability of flagellar protein export in the absence of FliH and FliI. The addition of FliH and FliI allowed the D45A, R85A, R94K and R270A mutant proteins to work even in the presence of the flhB(P28T) mutation. Suppressor analysis of a flhA(K203W) mutation showed an interaction between FlhA and FliR. Taken all together, we suggest that Asp-208 is directly involved in PMF-driven protein export and that the cooperative interactions of FlhA with FlhB, FliH, FliI, and FliR drive the translocation of export substrate

An energy transduction mechanism used in bacterial flagellar type III protein export

Flagellar proteins of bacteria are exported by a specific export apparatus. FliI ATPase forms a complex with FliH and FliJ and escorts export substrates from the cytoplasm to the export gate complex, which is made up of six membrane proteins. The export gate complex utilizes proton motive force across the cytoplasmic membrane for protein translocation, but the mechanism remains unknown. Here we show that the export gate complex by itself is a proton–protein antiporter that uses the two components of proton motive force, Δψ and ΔpH, for different steps of the protein export process. However, in the presence of FliH, FliI and FliJ, a specific binding of FliJ with an export gate membrane protein, FlhA, is brought about by the FliH–FliI complex, which turns the export gate into a highly efficient, Δψ-driven protein export apparatus