Role of support in photothermal carbon dioxide hydrogenation catalysed by Ni/CexTiyO2

Nickel was supported on varied ratios of ceria-titania mixed oxides(Ni/Ce_xTi_yO_2) to evaluate the role the support plays in photothermal carbon dioxide hydrogenation to produce methane. In a batch photothermal reactor system, Ni/CeO_2 achieved the highest conversion rate, reaching a conversion of 93% in approximately60–90 min. To decouple the influence of light and heat, the CO_2 hydrogenation was examined in an in-house designed photothermal reactor, whereby heat can be applied externally. Decoupling experiments revealed that heat from the thermalisation by light was the main driving force for the reaction. In addition, the conversion and temperature profile of the different catalysts revealed that the catalyst performance was governed by catalyst reducibility. H_2-TPR analyses showed that the Ni became more readily reducible with increasing Ce O_2 content,suggesting that the oxide plays a role in activating the Ni. The reduction temperature of the nickel catalyst(following a reduction and passivation process) was below 200 °C, which meant that the inherent heating temperature of the photothermal reactor was sufficient to initiate Ni/CexTiyO_2 catalyst activity. The exothermic methanation reaction was then able to heat the system further, ultimately reaching a temperature of 285 °C. The ancillary rise in temperature promotes further nickel reduction and methane formation, leading to a "snow-ball"effect. The findings demonstrate that, to achieve a "snow-ball" effect in a photothermal system, designing a catalyst which is easy to reduce, active for CO_2 hydrogenation, and capable of converting light to heat for its initial activation is critical.     

A population-specific HTR2B stop codon predisposes to severe impulsivity

Impulsivity, describing action without foresight, is an important feature of several psychiatric diseases, suicidality and violent behaviour. The complex origins of impulsivity hinder identification of the genes influencing it and the diseases with which it is associated. Here we perform exon-focused sequencing of impulsive individuals in a founder population, targeting fourteen genes belonging to the serotonin and dopamine domain. A stop codon in HTR2B was identified that is common (minor allele frequency >?1%) but exclusive to Finnish people. Expression of the gene in the human brain was assessed, as well as the molecular functionality of the stop codon, which was associated with psychiatric diseases marked by impulsivity in both population and family-based analyses. Knockout of Htr2b increased impulsive behaviours in mice, indicative of predictive validity. Our study shows the potential for identifying and tracing effects of rare alleles in complex behavioural phenotypes using founder populations, and indicates a role for HTR2B in impulsivity.     

Caenorhabditis elegans dpy-5 is a cuticle procollagen processed by a proprotein convertase

Genetic analysis of the nematode Caenorhabditis elegans reveals that all dpy-5 alleles are dominant suppressors of bli-4 blistering. Molecular cloning of dpy-5 establishes that it encodes a cuticle procollagen, defects in which are responsible for the short-body, dumpy phenotype. The null mutation, e907 removes the entire coding region, whereas the dpy-5 reference allele, e61, contains a nonsense substitution. RT-PCR analysis and a dpy-5::gfp fusion show that dpy-5 is expressed only in hypodermal cells at all post-embryonic life-cycle stages. Variable expression of dpy-5 in V lineage-derived seam cells suggests an alternative regulatory mechanism in these cells. The dpy-5 gene product contains an Arg-X-X-Arg cleavage motif that could be recognized by a proprotein convertase, such as BLI-4. Mutation of this site cause a dominant dumpy phenotype suggesting Dpy-5 procollagen requires processing for normal cuticle production. Received 13 January 2006; accepted 23 March 2006     

Cascades of multisite phosphorylation control Sic1 destruction at the onset of S phase

Multisite phosphorylation of proteins has been proposed to transform a graded protein kinase signal into an ultrasensitive switch-like response. Although many multiphosphorylated targets have been identified, the dynamics and sequence of individual phosphorylation events within the multisite phosphorylation process have never been thoroughly studied. In Saccharomyces cerevisiae, the initiation of S phase is thought to be governed by complexes of Cdk1 and Cln cyclins that phosphorylate six or more sites on the Clb5-Cdk1 inhibitor Sic1, directing it to SCF-mediated destruction. The resulting Sic1-free Clb5-Cdk1 complex triggers S phase. Here, we demonstrate that Sic1 destruction depends on a more complex process in which both Cln2-Cdk1 and Clb5-Cdk1 act in processive multiphosphorylation cascades leading to the phosphorylation of a small number of specific phosphodegrons. The routes of these phosphorylation cascades are shaped by precisely oriented docking interactions mediated by cyclin-specific docking motifs in Sic1 and by Cks1, the phospho-adaptor subunit of Cdk1. Our results indicate that Clb5-Cdk1-dependent phosphorylation generates positive feedback that is required for switch-like Sic1 destruction. Our evidence for a docking network within clusters of phosphorylation sites uncovers a new level of complexity in Cdk1-dependent regulation of cell cycle transitions, and has general implications for the regulation of cellular processes by multisite phosphorylation.     

Prolonged survival of AKR mice following allogeneic bone marrow transplantation

Zusammenfassung Die Mehrzahl der AKR Mäuse, die nach Immunosuppression und Transplantation von Knochenmark und lymphoiden Zellen allogener H₂-identischer Spender die «Graft-versus-Host» Reaktion überlebten, zeigten signifikant verlängerte mittlere Überlebenszeiten gegenüber Kontrolltieren, welche mit Immunosuppression allein oder Immunosuppression plus sygenen Zellen behandelt wurden.

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Supported by American Cancer Socitey Grant No. ET-55, a memorial to William Heller, Sr. and the Board of Trustees, Mount Sinai Medical Center.