Sialylation of campylobacter jejuni lipo-oligosaccharides: impact on phagocytosis and cytokine production in mice

<p>Background: Guillain-Barré syndrome (GBS) is a post-infectious polyradiculoneuropathy, frequently associated with antecedent Campylobacter jejuni (C. jejuni) infection. The presence of sialic acid on C. jejuni lipo-oligosaccharide (LOS) is considered a risk factor for development of GBS as it crucially determines the structural homology between LOS and gangliosides, explaining the induction of cross-reactive neurotoxic antibodies. Sialylated C. jejuni are recognised by TLR4 and sialoadhesin; however, the functional implications of these interactions in vivo are unknown.</p> <p>Methodology/Principal Findings: In this study we investigated the effects of bacterial sialylation on phagocytosis and cytokine secretion by mouse myeloid cells in vitro and in vivo. Using fluorescently labelled GM1a/GD1a ganglioside-mimicking C. jejuni strains and corresponding (Cst-II-mutant) control strains lacking sialic acid, we show that sialylated C. jejuni was more efficiently phagocytosed in vitro by BM-MΦ, but not by BM-DC. In addition, LOS sialylation increased the production of IL-10, IL-6 and IFN-β by both BM-MΦ and BM-DC. Subsequent in vivo experiments revealed that sialylation augmented the deposition of fluorescent bacteria in splenic DC, but not macrophages. In addition, sialylation significantly amplified the production of type I interferons, which was independent of pDC.</p> <p>Conclusions/Significance: These results identify novel immune stimulatory effects of C. jejuni sialylation, which may be important in inducing cross-reactive humoral responses that cause GBS</p&gt

An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers

Solar chromospheric observations of sunspot umbrae offer an exceptional view of magneto-hydrodynamic wave phenomena. In recent years, a wealth of wave signatures related to propagating magneto-acoustic modes have been presented, which demonstrate complex spatial and temporal structuring of the wave components. Theoretical modelling has demonstrated how these ubiquitous waves are consistent with an m=0 slow magneto-acoustic mode, which are excited by trapped sub-photospheric acoustic (p-mode) waves. However, the spectrum of umbral waves is broad, suggesting that the observed signatures represent the superposition of numerous frequencies and/or modes. We apply Fourier filtering, in both spatial and temporal domains, to extract chromospheric umbral wave characteristics consistent with an m=1 slow magneto-acoustic mode. This identification has not been described before. Angular frequencies of 0.037 +/- 0.007 rad/s (2.1 +/- 0.4 deg/s), corresponding to a period approximately 170 s for the m=1 mode are uncovered for spatial wavenumbers in the range of 0.45<k<0.90 arcsec^-1 (5000-9000 km). Theoretical dispersion relations are solved, with corresponding eigenfunctions computed, which allows the density perturbations to be investigated and compared with our observations. Such magnetohydrodynamic modelling confirms our interpretation that the identified wave signatures are the first direct observations of an m=1 slow magneto-acoustic mode in the chromospheric umbra of a sunspot

Environmentally Persistent Free Radicals (EPFRs). 3. Free versus Bound Hydroxyl Radicals in EPFR Aqueous Solutions

Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O17 water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO–OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations

Neutron spectroscopy of 26Mg states : Constraining the stellar neutron source 22Ne(α,n)25Mg

This work reports on accurate, high-resolution measurements of the 25Mg(n,γ)26Mg and 25Mg(n,tot) cross sections in the neutron energy range from thermal to about 300 keV, leading to a significantly improved 25Mg(n,γ)26Mg parametrization. The relevant resonances for n+25Mg were characterized from a combined R-matrix analysis of the experimental data. This resulted in an unambiguous spin/parity assignment of the corresponding excited states in 26Mg. With this information experimental upper limits of the reaction rates for 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg were established, potentially leading to a significantly higher (α,n)/(α,γ) ratio than previously evaluated. The impact of these results has been studied for stellar models in the mass range 2 to 25 M⊙

Neutron spectroscopy of ²⁶Mg states: Constraining the stellar neutron source ²²Ne(α,n)²⁵Mg

This work reports on accurate, high-resolution measurements of the 25Mg(n,γ)26Mg and 25Mg(n,tot) cross sections in the neutron energy range from thermal to about 300 keV, leading to a significantly improved 25Mg(n,γ)26Mg parametrization. The relevant resonances for n+25Mg were characterized from a combined R-matrix analysis of the experimental data. This resulted in an unambiguous spin/parity assignment of the corresponding excited states in 26Mg. With this information experimental upper limits of the reaction rates for 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg were established, potentially leading to a significantly higher (α,n)/(α,γ) ratio than previously evaluated. The impact of these results has been studied for stellar models in the mass range 2 to 25 M⊙

Gas phase synthesis and reactivity of dimethylaurate

A combination of multistage <annref idrefs="ann1">mass spectrometry</annref> experiments and DFT calculations were used to examine the synthesis and reactivity of <compname idrefs="chem1">dimethylaurate</compname>. <annref idrefs="ann2">Collision induced dissociation</annref> (<annref idrefs="ann2">CID</annref>) of [(CH<small>₃</small>CO<small>₂</small>)<small>₄</small>Au]<small>⁻</small> proceeded <em>via</em> reductive elimination of <compname idrefs="chem3">acetylperoxide</compname> to yield the <annref idrefs="ann3">diacetate</annref> [CH<small>₃</small>CO<small>₂</small>AuO<small>₂</small>CCH<small>₃</small>]<small>⁻</small>, which in turn underwent sequential <annref idrefs="ann2">CID</annref> decarboxylation reactions to yield the organoaurates [CH<small>₃</small>CO<small>₂</small>AuCH<small>₃</small>]<small>⁻</small> and [CH<small>₃</small>AuCH<small>₃</small>]<small>⁻</small>. The unimolecular chemistry of the <annref idrefs="ann3">dimethylaurate</annref> proceeds <em>via</em> a combination of bond homolysis to yield the <annref idrefs="ann4">methyl</annref> aurate <annref idrefs="ann5">radical anion</annref> [CH<small>₃</small>Au]˙<small>⁻</small> as well as formation of the <compname idrefs="chem4">gold dihydride</compname> [<compname idrefs="chem5">HAuH</compname>]<small>⁻</small>. DFT calculations reveal that the latter anion is formed <em>via</em> a 1,2-dyotropic <annref idrefs="ann6">rearrangement</annref> to yield the isomer [CH<small>₃</small>CH<small>₂</small>AuH]<small>⁻</small>, followed by a <annref idrefs="ann3">β-hydride</annref> <annref idrefs="ann7">elimination reaction</annref>. Ion-molecule reactions of [CH<small>₃</small>AuCH<small>₃</small>]<small>⁻</small> with <compname idrefs="chem6">methyl iodide</compname> did not yield any products even at relatively high concentrations of the neutral substrate and longer reaction times, indicating a reaction efficiency of less than 1 in 20 000 collisions. DFT calculations were carried out on two different potential energy surfaces (<annref idrefs="ann8">PES</annref>) for the reaction of [CH<small>₃</small>AuCH<small>₃</small>]<small>⁻</small> with CH<small>₃</small>I: (i) an S<small>_N</small>2 mechanism proceeding <em>via</em> a side-on transition state; and (ii) a stepwise mechanism proceeding <em>via</em> oxidative addition followed by reductive elimination. Both pathways have significant endothermic barriers, consistent with the lack of C–C bond coupling products being formed in the experiments. Finally, the reactivity of [CH<small>₃</small>AuCH<small>₃</small>]<small>⁻</small> is compared to the previously studied [CH<small>₃</small>AgCH<small>₃</small>]<small>⁻</small> and [CH<small>₃</small>CuCH<small>₃</small>]<small>⁻</small>, as well as condensed phase studies on <compname idrefs="chem1">dimethylaurate</compname> salts

sp-sp(3) Coupling reactions of alkynylsilver cations, RC (equivalent to) CAg2+ (R = Me and Ph) with allyliodide

Alkynylsilver cations, RC equivalent to CAg2+ (where R = Me and Ph) have been prepared in the gas phase using multistage mass spectrometry experiments in a quadrupole ion trap mass spectrometer. Two methods were used: (i) electrospray ionisation (ESI) of a mixture of AgNO3 (in MeOH/H2O/acetic acid) and the alkyne carboxylic acid to yield the appropriate silver acetylide cations RC equivalent to CAg2+, via a facile decarboxylation of the RC equivalent to CCO2Ag2+ precursor; (ii) ESI of silver acetylides, RCuCAg, which yields a cluster of the type, [(RC equivalent to CAg) 12Ag2Cl](+). Regardless of the method of preparation, these alkynylsilver cations, RCuCAg2+, undergo ion-molecule reactions with allyliodide to yield the ionic products Ag(2)l(+) and [(RC equivalent to CCH2CH=CH2)Ag](+). The CID spectrum of [(PhC equivalent to CCH2CH=CH2)Ag](+) was compared to that of an authentic sample of the silver adduct of 5-phenyl-1-penten-4-yne. Both ions fragment to yield Ag+ and the radical cation, PhC equivalent to CCH2CH=CH2+., confirming that C-C bond coupling has taken place in the gas phase. DFT calculations were carried out on these C-C bond coupling reactions for the system R = Me. The reaction is highly exothermic and involves the initial coordination of the allyliodide to both silver atoms, with the iodine coordinating to one atom and the alkene moiety coordinating to the other. The overall mechanism of C-C bond coupling involves oxidative addition of the allyliodide followed by reductive elimination of RC equivalent to CCH2CH=CH2, to ultimately yield two sets of reaction products: (i) Ag(2)l(+) and RC equivalent to CCH2CH=CH2; and (ii) [(RC equivalent to CCH2CH=CH2)Ag](+) and Agl