Gas-phase CO depletion and N2H+ abundances in starless cores

Seven isolated, nearby low-mass starless molecular cloud cores have been observed as part of the Herschel key program Earliest Phases of Star formation (EPoS). By applying a ray-tracing technique to the obtained continuum emission and complementary (sub)mm emission maps, we derive the physical structure (density, dust temperature) of these cloud cores. We present observations of the 12CO, 13CO, and C18O (2-1) and N2H+ (1-0) transitions towards the same cores. Based on the density and temperature profiles, we apply time-dependent chemical and line-radiative transfer modeling and compare the modeled to the observed molecular emission profiles. CO is frozen onto the grains in the center of all cores in our sample. The level of CO depletion increases with hydrogen density and ranges from 46% up to more than 95% in the core centers in the core centers in the three cores with the highest hydrogen density. The average hydrogen density at which 50% of CO is frozen onto the grains is 1.1+-0.4 10^5 cm^-3. At about this density, the cores typically have the highest relative abundance of N2H+. The cores with higher central densities show depletion of N2H+ at levels of 13% to 55%. The chemical ages for the individual species are on average 2+-1 10^5 yr for 13CO, 6+-3 10^4 yr for C18O, and 9+-2 10^4 yr for N2H+. Chemical modeling indirectly suggests that the gas and dust temperatures decouple in the envelopes and that the dust grains are not yet significantly coagulated. We observationally confirm chemical models of CO-freezeout and nitrogen chemistry. We find clear correlations between the hydrogen density and CO depletion and the emergence of N2H+. The chemical ages indicate a core lifetime of less than 1 Myr.Comment: 24 pages, 25 figures, Accepted for publication in Astronomy and Astrophysic

Intron RNA editing is essential for splicing in plant mitochondria

Most plant mitochondria messenger RNAs (mRNAs) undergo editing through C-to-U conversions located mainly in exon sequences. However, some RNA editing events are found in non-coding regions at critical positions in the predicted secondary and tertiary structures of introns, suggesting that RNA editing could be important for splicing. Here, we studied the relationships between editing and splicing of the mRNA encoding the ribosomal protein S10 (rps10), which has a group II intron and five editing sites. Two of them, C2 and C3, predicted to stabilize the folded structure of the intron necessary for splicing, were studied by using rps10 mutants introduced into isolated potato mitochondria by electroporation. While mutations of C2 involved in EBS2/IBS2 interactions did not affect splicing, probably by the presence of an alternative EBS2′ region in domain I of the intron, the edition of site C3 turned out to be critical for rps10 mRNA splicing; only the edited (U) form of the transcript was processed. Interestingly, RNA editing was strongly reduced in transcripts from two different intronless genes, rps10 from potato and cox2 from wheat, suggesting that efficient RNA processing may require a close interaction of factors engaged in different maturation processes. This is the first report linking editing and splicing in conditions close to the in vivo situation

Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Modulation of defense signal transduction by flagellin-induced WRKY41 transcription factor in Arabidopsis thaliana

Flagellin, a component of the flagellar filament of Pseudomonas syringae pv. tabaci 6605 (Pta), induces hypersensitive reaction in its non-host Arabidopsis thaliana. We identified the WRKY41 gene, which belongs to a multigene family encoding WRKY plant-specific transcription factors, as one of the flagellin-inducible genes in A. thaliana. Expression of WRKY41 is induced by inoculation with the incompatible pathogen P. syringae pv. tomato DC3000 (Pto) possessing AvrRpt2 and the non-host pathogens Pta within 6-h after inoculation, but not by inoculation with the compatible Pto. Expression of WRKY41 was also induced by inoculation of A. thaliana with an hrp-type three secretion system (T3SS)-defective mutant of Pto, indicating that effectors produced by T3SS in the Pto wild-type suppress the activation of WRKY41. Arabidopsis overexpressing WRKY41 showed enhanced resistance to the Pto wild-type but increased susceptibility to Erwinia carotovora EC1. WRKY41-overexpressing Arabidopsis constitutively expresses the PR5 gene, but suppresses the methyl jasmonate-induced PDF1.2 gene expression. These results demonstrate that WRKY41 may be a key regulator in the cross talk of salicylic acid and jasmonic acid pathways.</p

All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations

In ultra-high resolution (UHR-) optical coherence tomography (OCT) group velocity dispersion (GVD) must be corrected for in order to approach the theoretical resolution limit. One approach promises not only compensation, but complete annihilation of even order dispersion effects, and that at all sample depths. This approach has hitherto been demonstrated with an experimentally demanding ‘balanced detection’ configuration based on using two detectors. We demonstrate intensity correlation (IC) OCT using a conventional spectral domain (SD) UHR-OCT system with a single detector. IC-SD-OCT configurations exhibit cross term ghost images and a reduced axial range, half of that of conventional SD-OCT. We demonstrate that both shortcomings can be removed by applying a generic artefact reduction algorithm and using analytic interferograms. We show the superiority of IC-SD-OCT compared to conventional SD-OCT by showing how IC-SD-OCT is able to image spatial structures behind a strongly dispersive silicon wafer. Finally, we question the resolution enhancement of 2–? that IC-SD-OCT is often believed to have compared to SD-OCT. We show that this is simply the effect of squaring the reflectivity profile as a natural result of processing the product of two intensity spectra instead of a single spectrum

Direct Detection of Antibody Concentration and Affinity in Human Serum Using Microscale Thermophoresis

The direct quantification of both the binding affinity and absolute concentration of disease-related biomarkers in biological fluids is particularly beneficial for differential diagnosis and therapy monitoring. Here, we extend microscale thermophoresis to target immunological questions. Optically generated thermal gradients were used to deplete fluorescently marked antigens in 2- and 10-fold-diluted human serum. We devised and validated an autocompetitive strategy to independently fit the concentration and dissociation constant of autoimmune antibodies against the cardiac beta 1-adrenergic receptor related to dilated cardiomyopathy. As an artificial antigen, the peptide CORI was designed to mimic the second extracellular receptor loop. Thermophoresis resolved antibody concentrations from 2 to 200 nM and measured the dissociation constant as 75 nM. The approach quantifies antibody binding in its native serum environment within microliter volumes and without any surface attachments. The simplicity of the mix and probe protocol minimizes systematic errors, making thermophoresis a promising detection method for personalized medicine

Polarization sensitive OCT with needle probes

We demonstrate polarization sensitive OCT using miniaturized needle probes. Employing the Mueller-formalism, we reconstruct tissue birefringence and retrieve the depolarization index of ex vivo tissue samples, providing contrast complementary to the structural intensity signal