Catalytic and mechanistic studies of a highly active and E-selective Co(II) PNNH pincer catalyst system for transfer-semihydrogenation of internal alkynes

Herein we report the application of a Co(II) PNNH pincer catalyst system (PNNH = 2-(5-(t-butyl)-1H-pyrazol-3-yl)-6-(dialkylphosphinomethyl)pyridine) for the highly E-selective transfer semihydrogenation of internal diaryl alkynes using methanol and ammonia borane...

Selective Transfer of Maternal Antibodies in Preterm and Term Children

Preterm newborns are more likely to suffer from infectious diseases at birth compared to children delivered at term. Whether this is due to compromised cellular, humoral, or organ-specific development remains unclear. Recent studies have shown that while preterm children have an aberrant cellular immune response, these infants receive similar maternal anti-viral IgG repertoires compared to term children, albeit at lower concentrations. These data point to selectivity in placental transfer at distinct gestational ages, to ensure that children are endowed with the most robust humoral immunity even if born preterm. To begin to define the mechanism by which preterm selective transfer may occur, the overall quantity and functional quality of an array of vaccine-, endemic pathogen-, and common antigen-specific antibodies were assessed across a cohort of 11 preterm and 12 term-delivered mother:infant pairs from birth through week 12. Although higher antibody levels were present in term infants, the overall functional profiles of antigen-specific antibodies were very similar. Temporal transfer differences were ascertained across distinct antibody subpopulations, with early transfer of functional antibodies capable of binding to FcRn and FcγR2-3 receptors followed by the transfer of distinct IgG subclasses. These results provide new insights on maternal:fetal immunity, highlighting novel immune axes that may be manipulated to enhance neonatal immune transfer of antibodies through gestation.

Highly Functional Group Tolerant, (E)-Selective Transfer Semihydrogenation of Alkynes Catalysed by Iridium Complex Bearing Unsymmetrical Ferrocene-Based Phosphine Ligand

Herein, we present (E)-selective transfer semihydrogenation of alkynes based on in situ generated iridium complex from [Ir(COD)Cl]2 and unsymmetrical ferrocene-based phosphine ligand in the presence of formic acid as a hydrogen donor. The catalytic system is distinguished by unprecedented chemoselectivity and exceptional stereoselectivity substantiated by the broad scope of test-ed substrates, including natural products derivatives. The uniform reaction conditions may be applied to various alkynes, owing to a lack of over-reduction. The intriguing difference in catalytic activity between unsymmetrical and symmetrical ferrocene-based ligands was attributed to diver-gent coordination and steric hindrance. The presented methodology constitutes a solution to the common limitations of the published catalytic systems.

Highly Functional Group Tolerant, (E)-Selective Transfer Semihydrogenation of Alkynes Catalysed by Iridium Complex Bearing Unsymmetrical Ferrocene-Based Phosphine Ligand

Herein, we present (E)-selective transfer semihydrogenation of alkynes based on in situ generated iridium complex from [Ir(COD)Cl]2 and unsymmetrical ferrocene-based phosphine ligand in the presence of formic acid as a hydrogen donor. The catalytic system is distinguished by unprecedented chemoselectivity and exceptional stereoselectivity substantiated by the broad scope of test-ed substrates, including natural products derivatives. The uniform reaction conditions may be applied to various alkynes, owing to a lack of over-reduction. The intriguing difference in catalytic activity between unsymmetrical and symmetrical ferrocene-based ligands was attributed to diver-gent coordination and steric hindrance. The presented methodology constitutes a solution to the common limitations of the published catalytic systems.

From peridotite to fuchsite bearing quartzite via carbonation and weathering: with implications for the Pb budget of continental crust

Extensive carbonation of peridotite results in listvenite, a rock composed of magnesite and quartz. At Gråberget, Røros, SE-Norway, a variably serpentinized peridotite body, surrounded by the Røros schists, a former abyssal sediment displays all stages of transformation of peridotite to quartzite. In this paper we record the sequence of steps in this process by combining the observation of mineral assemblages, textural relationships and geochemistry, and variations in Pb isotopic compositions. Initial serpentinization, a stage that also involved an enrichment in fluid-mobile elements (Pb, Sb and As), was followed by carbonation through CO2 fluids that formed soapstone, and eventually listvenite. The listvenite grades by decreasing amounts of carbonates into fuchsite bearing quartzite. The carbonates dissolved during supergene alteration and formed pores coated with oxides of Fe, Mn and Ni resulting in a brown rock color. The quartzite displays porous stylolites enriched in Pb, As and Sb and fuchsite with porous chromite grains as the only relicts of the original mineralogy in the peridotite. The dissolution of the carbonate occurred at oxidizing conditions at temperatures below 150 °C, where the solubility of magnesite is higher than that of quartz. Formation of quartzite from peridotite is supported by low REE contents and lack of zircons in the two rock types. The transformation involved enrichment of Pb, coupled with the elimination of Mg and enrichment of Si. This chemical fractionation and selective transfer of elements to the continents is an important mechanism and needs to be taken into account in models of continental evolution.