Browsing by Subject "copper"

Now showing 1 - 4 of 4
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    Data supporting: Evaluation of a decade of management of a North American aquatic invasive species (Nitellopsis obtusa) highlights scale-dependent effectiveness and monitoring gaps
    (2024-11-25) Glisson, Wesley; Nault, Michelle; Jurek, Chris; Fischer, Eric; Lund, Keegan; Bloodsworth Cattoor, Kylie; Londo, April; Hauck-Jacobs, Emelia; Egdell, Rod; McComas, Steve; Fieldseth, Eric; Larkin, Daniel; djlarkin@umn.edu; Larkin, Daniel; Minnesota Aquatic Invasive Species Research Center (MAISRC); Department of Fisheries, Wildlife and Conservation Biology
    Nitellopsis obtusa (starry stonewort) is an invasive macroalga subject to substantial control efforts in the Midwestern United States; however, there has not been systematic evaluation of treatment effectiveness. We synthesized management approaches and outcomes using monitoring performed over a decade-long period across 38 lakes in Indiana, Wisconsin, and Minnesota. We compiled all available point-intercept (PI) survey data from lakes where N. obtusa was known to occur since the year the species was first discovered in each state (Indiana, 2008; Wisconsin, 2014; Minnesota, 2015) until 2018 (Indiana) and 2019 (Wisconsin and Minnesota). These data comprised raw survey and summary data from whole-lake PI surveys, as well as targeted sub-PI surveys within managed areas. We compiled all available information on N. obtusa management for the time periods encompassing the survey data. Management data were collected from: 1) pesticide application records (PARs; Minnesota), 2) chemical treatment and mechanical harvesting records (Wisconsin), 3) aquatic vegetation management plans (AVMPs; Indiana), and 4) direct knowledge of known management events (all states). We compiled as much information as possible for each management action on each lake. For hand pulling, we additionally compiled all available data on the biomass of N. obtusa removed during each event; we included all such data through 2022.
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    Information Circular 10. Copper and Nickel Resources in the Duluth Complex, Northeastern Minnesota
    (Minnesota Geological Survey, 1974) Bonnichsen, Bill
    The Ely-Hoyt Lakes region, in northeastern Minnesota, contains very large quantities of disseminated copper and nickel sulfides that are potentially minable. The principal sulfides are pyrrhotite, chalcopyrite, cubanite, and pentlandite, and the average copper-nickel ratio in the sulfide concentrations is approximately 3:1. The sulfides are associated with the northwestern margin of the Duluth Complex, a large mafic igneous pluton of Late Precambrian age, and occur principally within the basal zone of the intrusion. A conservative estimate of the metal resources in the Ely-Hoyt Lakes region, based on assay data available from 24 drill holes, and a cutoff grade, or lower mining limit, of 0.5 percent combined copper and nickel indicates 13.8 million tons of copper and 4.6 million tons of nickel having a gross value of $27 billion. Although the copper and nickel deposits in the Ely-Hoyt Lakes region are marginal economically, they constitute one of the United States' principal metal resources.
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    Investigation of the structure and reactivity of a series of mono- and dicopper complexes supported by biomimetic ligands
    (2019-06) Elwell, Courtney
    Currently, selective oxidation of C–H bonds is a primary challenge in the organic synthesis of essential chemicals, including alternative fuels and pharmaceuticals. Nature carries out selective oxidations of C–H bonds via the use of copper-based monooxygenase (MO) enzymes such as lytic polysaccharide monooxygenase (LPMO). Research efforts in the Tolman group aim to model the copper-oxygen reactive intermediates of MO enzymes via synthesis of synthetic small molecule mimics. In Chapter 1, I will outline the proposed copper-oxygen intermediates for MO enzymes and discuss, in detail, the spectroscopic features and reactivity observed for synthetic mimics of these cores. Chapter 2 describes my efforts to synthesize a monoanionic ligand, bis(quinolinylcarbonyl)amide (–L1), that closely models the LPMO active site. The organic synthesis of HL1 as well as isolation of structurally diverse mono- and dinuclear copper complexes supported by –L1 via X-ray crystallography will be discussed. In addition, the fate of this ligand as a synthetic model of enzymatic active sites is assessed. In Chapter 3, I present the investigation of a novel copper(III)-benzoate complex supported by a dianionic bis(arylcarboxamido)pyridine ligand, LCuIII(O2CC6H4(Cl)), which is shown to undergo proton-coupled electron transfer (PCET) with O–H and C–H substrates. Comparison of the PCET reactivity of LCuIII(O2CC6H4(Cl)) with previously reported LCuIII(OH) and LCuIII(OOR) reveals the effect of the fourth ligand on [LCuIII]+ reactivity. In addition, mechanistic conclusions for each copper(III) complex are discussed with significant insight provided from time dependent-density functional theory (TD-DFT) and intrinsic bond order (IBO) analysis completed by Mukunda Mandal, a graduate student in the group of Professor Christopher Cramer. Chapter 4 investigates the spectroscopic features and PCET reactivity of a series of formally copper(III)-carboxylates supported by L2–, LCuIII(O2C–R), with the aim of understanding how electronic modification of the carboxylate ligand effects the observed properties and reactivity of the complexes. The reactivity trends of LCuIII(O2C–R) complexes with O–H and C–H bonds will be detailed as well as the implications of such trends on the mechanism of the reaction of LCuIII(O2C–R) complexes with substrates. Lastly, in Chapter 5, I present the study of a water soluble CuIII(OH) complex, [SO3LCu(OH)]2–, to investigate its ability to act as a water oxidation catalyst. The results of pH-dependent spectroscopic and electrochemical studies are detailed and the aqueous reactivity of [SO3LCu(OH)]2– with C–H substrates is discussed.
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    Modeling the Active Sites of Copper Monooxygenase Enzymes
    (2017-07) Neisen, Benjamin
    Mechanistic investigation of copper-oxygen intermediates relevant to the oxygenation reactions of copper monooxygenase enzymes is a long-standing goal of bioinorganic chemists. To elucidate and understand the key species in copper monooxygenase pathways, small molecule synthetic chemistry has been employed to discretely generate and characterize individual species of interest. In Chapter 1, previous enzymatic and modeling work with respect to copper monooxygenase chemistry is discussed and current mechanistic proposals are explored in detail. Chapter 2 describes modeling studies of monocopper sites and the influence of secondary sphere hydrogen bonding interactions on their redox behavior. A series of monocopper complexes with secondary sphere hydrogen bond interactions were determined to result in large increases of the electrochemical potentials of the CuIII/CuII redox couple when compared to non-hydrogen bound analogs. The hydrogen bonding model systems provide evidence for the structure-function relationship of secondary coordination influences on metal-containing active sites. Chapter 3 discusses development of a previously undescribed dinucleating macrocyclic ligand, designed to support dicopper-oxygen cores relevant to the enzyme particulate methane monooxygenase (pMMO). Attempts to generate dicopper-hydroxo type cores resulted in hydrolytic products found to be dicopper complexes that were crystallographically characterized. Observed “paddle wheel” type configurations with cis-labile coordination sites in the dicopper complexes represent a class of compounds with diverse coordination chemistry. The final chapter (Chapter 4) describes the synthesis and characterization of a formal CuIII-alkylperoxo core utilizing spectroscopic and computational methods. The CuIII-alkylperoxo complex has been shown to undergo proton-coupled electron-transfer (PCET) reactions with weak O-H bond substrates. The CuIII-alkylperoxo core is considered to be a model system of a CuIII-OOH core, proposed to be a possible reactive intermediate in lytic polysaccharide monooxygenase (LPMO).