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  • 1
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    N(2)reduction and hydrogenation to ammonia by a molecular iron-potassium complex (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-11-15
    Description: The most common catalyst in the Haber-Bosch process for the hydrogenation of dinitrogen (N(2)) to ammonia (NH(3)) is an iron surface promoted with potassium cations (K(+)), but soluble iron complexes have neither reduced the N-N bond of N(2) to nitride (N(3-)) nor produced large amounts of NH(3) from N(2). We report a molecular iron complex that reacts with N(2) and a potassium reductant to give a complex with two nitrides, which are bound to iron and potassium cations. The product has a Fe(3)N(2) core, implying that three iron atoms cooperate to break the N-N triple bond through a six-electron reduction. The nitride complex reacts with acid and with H(2) to give substantial yields of N(2)-derived ammonia. These reactions, although not yet catalytic, give structural and spectroscopic insight into N(2) cleavage and N-H bond-forming reactions of iron.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3218428/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3218428/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rodriguez, Meghan M -- Bill, Eckhard -- Brennessel, William W -- Holland, Patrick L -- GM-065313/GM/NIGMS NIH HHS/ -- R01 GM065313/GM/NIGMS NIH HHS/ -- R01 GM065313-08/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2011 Nov 11;334(6057):780-3. doi: 10.1126/science.1211906.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22076372" target="_blank"〉PubMed〈/a〉
    Keywords: Acids/chemistry ; Ammonia/*chemistry ; Catalysis ; Crystallography, X-Ray ; Ferric Compounds/*chemistry ; Ferrous Compounds/*chemistry ; Graphite/chemistry ; Hydrogenation ; Molecular Structure ; Nitrogen/*chemistry ; Oxidation-Reduction ; Physicochemical Processes ; Potassium/chemistry ; Potassium Compounds/*chemistry ; Spectroscopy, Mossbauer
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Robust photogeneration of H2 in water using semiconductor nanocrystals and a nickel catalyst (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-11-10
    Description: Homogeneous systems for light-driven reduction of protons to H(2) typically suffer from short lifetimes because of decomposition of the light-absorbing molecule. We report a robust and highly active system for solar hydrogen generation in water that uses CdSe nanocrystals capped with dihydrolipoic acid (DHLA) as the light absorber and a soluble Ni(2+)-DHLA catalyst for proton reduction with ascorbic acid as an electron donor at pH = 4.5, which gives 〉600,000 turnovers. Under appropriate conditions, the precious-metal-free system has undiminished activity for at least 360 hours under illumination at 520 nanometers and achieves quantum yields in water of over 36%.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Han, Zhiji -- Qiu, Fen -- Eisenberg, Richard -- Holland, Patrick L -- Krauss, Todd D -- New York, N.Y. -- Science. 2012 Dec 7;338(6112):1321-4. doi: 10.1126/science.1227775. Epub 2012 Nov 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23138979" target="_blank"〉PubMed〈/a〉
    Keywords: Cadmium Compounds/chemistry ; Catalysis ; Hydrogen/*chemistry ; Nickel/*chemistry ; *Photochemical Processes ; *Quantum Dots ; Selenium Compounds/chemistry ; Thioctic Acid/analogs & derivatives/chemistry ; Water/*chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Binding of dinitrogen to an iron-sulfur-carbon site (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-09-30
    Description: Nitrogenases are the enzymes by which certain microorganisms convert atmospheric dinitrogen (N2) to ammonia, thereby providing essential nitrogen atoms for higher organisms. The most common nitrogenases reduce atmospheric N2 at the FeMo cofactor, a sulfur-rich iron-molybdenum cluster (FeMoco). The central iron sites that are coordinated to sulfur and carbon atoms in FeMoco have been proposed to be the substrate binding sites, on the basis of kinetic and spectroscopic studies. In the resting state, the central iron sites each have bonds to three sulfur atoms and one carbon atom. Addition of electrons to the resting state causes the FeMoco to react with N2, but the geometry and bonding environment of N2-bound species remain unknown. Here we describe a synthetic complex with a sulfur-rich coordination sphere that, upon reduction, breaks an Fe-S bond and binds N2. The product is the first synthetic Fe-N2 complex in which iron has bonds to sulfur and carbon atoms, providing a model for N2 coordination in the FeMoco. Our results demonstrate that breaking an Fe-S bond is a chemically reasonable route to N2 binding in the FeMoco, and show structural and spectroscopic details for weakened N2 on a sulfur-rich iron site.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592811/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592811/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Coric, Ilija -- Mercado, Brandon Q -- Bill, Eckhard -- Vinyard, David J -- Holland, Patrick L -- GM065313/GM/NIGMS NIH HHS/ -- R01 GM065313/GM/NIGMS NIH HHS/ -- England -- Nature. 2015 Oct 1;526(7571):96-9. doi: 10.1038/nature15246. Epub 2015 Sep 23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA. ; Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mulheim an der Ruhr, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26416755" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Carbon/*chemistry ; Electrons ; Iron/*chemistry ; Ligands ; Molybdoferredoxin/chemistry/metabolism ; Nitrogen/*chemistry ; Nitrogenase/metabolism ; Sulfur/*chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 4
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    Cobalt-dithiolene complexes for the photocatalytic and electrocatalytic reduction of protons in aqueous solutions (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-06-12
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 5
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    A Burst of miRNA Innovation in the Early Evolution of Butterflies and Moths (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-25
    Description: MicroRNAs (miRNAs) are involved in posttranscriptional regulation of gene expression. Because several miRNAs are known to affect the stability or translation of developmental regulatory genes, the origin of novel miRNAs may have contributed to the evolution of developmental processes and morphology. Lepidoptera (butterflies and moths) is a species-rich clade with a well-established phylogeny and abundant genomic resources, thereby representing an ideal system in which to study miRNA evolution. We sequenced small RNA libraries from developmental stages of two divergent lepidopterans, Cameraria ohridella (Horse chestnut Leafminer) and Pararge aegeria (Speckled Wood butterfly), discovering 90 and 81 conserved miRNAs, respectively, and many species-specific miRNA sequences. Mapping miRNAs onto the lepidopteran phylogeny reveals rapid miRNA turnover and an episode of miRNA fixation early in lepidopteran evolution, implying that miRNA acquisition accompanied the early radiation of the Lepidoptera. One lepidopteran-specific miRNA gene, miR-2768, is located within an intron of the homeobox gene invected , involved in insect segmental and wing patterning. We identified cubitus interruptus ( ci ) as a likely direct target of miR-2768, and validated this suppression using a luciferase assay system. We propose a model by which miR-2768 modulates expression of ci in the segmentation pathway and in patterning of lepidopteran wing primordia.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 6
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    Cobalt-dithiolene complexes for proton reduction. [Chemistry] (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-09-26
    Description: Artificial photosynthesis (AP) is a promising method of converting solar energy into fuel (H2). Harnessing solar energy to generate H2 from H+ is a crucial process in systems for artificial photosynthesis. Widespread application of a device for AP would rely on the use of platinum-free catalysts due to the scarcity...
    Keywords: Chemical Approaches to Artificial Photosynthesis: Solar Fuels Special Feature
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Beyond fossil fuel-driven nitrogen transformations (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-05-25
    Description: Nitrogen is fundamental to all of life and many industrial processes. The interchange of nitrogen oxidation states in the industrial production of ammonia, nitric acid, and other commodity chemicals is largely powered by fossil fuels. A key goal of contemporary research in the field of nitrogen chemistry is to minimize the use of fossil fuels by developing more efficient heterogeneous, homogeneous, photo-, and electrocatalytic processes or by adapting the enzymatic processes underlying the natural nitrogen cycle. These approaches, as well as the challenges involved, are discussed in this Review.
    Keywords: Chemistry, Online Only
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    [3Fe-4S] proteins catalyze tRNA thiolation [Biochemistry] (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-11-09
    Description: The sulfur-containing nucleosides in transfer RNA (tRNAs) are present in all three domains of life; they have critical functions for accurate and efficient translation, such as tRNA structure stabilization and proper codon recognition. The tRNA modification enzymes ThiI (in bacteria and archaea) and Ncs6 (in archaea and eukaryotic cytosols) catalyze...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Boron compounds tackle dinitrogen (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-02-23
    Keywords: Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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