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

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

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

Neuronal circuitry for pain processing in the dorsal horn

Neurons in the spinal dorsal horn process sensory information, which is then transmitted to several brain regions, including those responsible for pain perception. The dorsal horn provides numerous potential targets for the development of novel analgesics and is thought to undergo changes that contribute to the exaggerated pain felt after nerve injury and inflammation. Despite its obvious importance, we still know little about the neuronal circuits that process sensory information, mainly because of the heterogeneity of the various neuronal components that make up these circuits. Recent studies have begun to shed light on the neuronal organization and circuitry of this complex region

A chain mechanism for flagellum growth.

Bacteria swim by means of long flagella extending from the cell surface. These are assembled from thousands of protein subunits translocated across the cell membrane by an export machinery at the base of each flagellum. Unfolded subunits then transit through a narrow channel at the core of the growing flagellum to the tip, where they crystallize into the nascent structure. As the flagellum lengthens outside the cell, the rate of flagellum growth does not change. The mystery is how subunit transit is maintained at a constant rate without a discernible energy source in the channel of the external flagellum. We present evidence for a simple physical mechanism for flagellum growth that harnesses the entropic force of the unfolded subunits themselves. We show that a subunit docked at the export machinery can be captured by a free subunit through head-to-tail linkage of juxtaposed amino (N)- and carboxy (C)-terminal helices. We propose that sequential rounds of linkage would generate a multisubunit chain that pulls successive subunits into and through the channel to the flagellum tip, and by isolating filaments growing on bacterial cells we reveal the predicted chain of head-to-tail linked subunits in the transit channel of flagella. Thermodynamic analysis confirms that links in the subunit chain can withstand the pulling force generated by rounds of subunit crystallization at the flagellum tip, and polymer theory predicts that as the N terminus of each unfolded subunit crystallizes, the entropic force at the subunit C terminus would increase, rapidly overcoming the threshold required to pull the next subunit from the export machinery. This pulling force would adjust automatically over the increasing length of the growing flagellum, maintaining a constant rate of subunit delivery to the tip

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

Specific Evolution of F1-Like ATPases in Mycoplasmas

F1F0 ATPases have been identified in most bacteria, including mycoplasmas which have very small genomes associated with a host-dependent lifestyle. In addition to the typical operon of eight genes encoding genuine F1F0 ATPase (Type 1), we identified related clusters of seven genes in many mycoplasma species. Four of the encoded proteins have predicted structures similar to the α, β, γ and ε subunits of F1 ATPases and could form an F1-like ATPase. The other three proteins display no similarity to any other known proteins. Two of these proteins are probably located in the membrane, as they have three and twelve predicted transmembrane helices. Phylogenomic studies identified two types of F1-like ATPase clusters, Type 2 and Type 3, characterized by a rapid evolution of sequences with the conservation of structural features. Clusters encoding Type 2 and Type 3 ATPases were assumed to originate from the Hominis group of mycoplasmas. We suggest that Type 3 ATPase clusters may spread to other phylogenetic groups by horizontal gene transfer between mycoplasmas in the same host, based on phylogeny and genomic context. Functional analyses in the ruminant pathogen Mycoplasma mycoides subsp. mycoides showed that the Type 3 cluster genes were organized into an operon. Proteomic analyses demonstrated that the seven encoded proteins were produced during growth in axenic media. Mutagenesis and complementation studies demonstrated an association of the Type 3 cluster with a major ATPase activity of membrane fractions. Thus, despite their tendency toward genome reduction, mycoplasmas have evolved and exchanged specific F1-like ATPases with no known equivalent in other bacteria. We propose a model, in which the F1-like structure is associated with a hypothetical X0 sector located in the membrane of mycoplasma cells

Loss of yata, a Novel Gene Regulating the Subcellular Localization of APPL, Induces Deterioration of Neural Tissues and Lifespan Shortening

Background: The subcellular localization of membrane and secreted proteins is finely and dynamically regulated through intracellular vesicular trafficking for permitting various biological processes. Drosophila Amyloid precursor protein like (APPL) and Hikaru genki (HIG) are examples of proteins that show differential subcellular localization among several developmental stages. Methodology/Principal Findings: During the study of the localization mechanisms of APPL and HIG, we isolated a novel mutant of the gene, CG1973, which we named yata. This molecule interacted genetically with Appl and is structurally similar to mouse NTKL/SCYL1, whose mutation was reported to cause neurodegeneration. yata null mutants showed phenotypes that included developmental abnormalities, progressive eye vacuolization, brain volume reduction, and lifespan shortening. Exogenous expression of Appl or hig in neurons partially rescued the mutant phenotypes of yata. Conversely, the phenotypes were exacerbated in double null mutants for yata and Appl. We also examined the subcellular localization of endogenous APPL and exogenously pulse-induced APPL tagged with FLAG by immunostaining the pupal brain and larval motor neurons in yata mutants. Our data revealed that yata mutants showed impaired subcellular localization of APPL. Finally, yata mutant pupal brains occasionally showed aberrant accumulation of Sec23p, a component of the COPII coat of secretory vesicles traveling from the endoplasmic reticulum (ER) to the Golgi