Publications by authors named "DR Armstrong"

Anticoagulation management in pediatric extracorporeal membrane oxygenation (ECMO) is challenging with multiple laboratory measures utilized across institutions without consensus guidelines. These include partial thromboplastin time (PTT), thromboelastography (TEG), and antifactor Xa (aXa). We aimed to evaluate the consistency of TEG R-time, PTT, and aXa correlation to bivalirudin and heparin dosing.

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Two studies were conducted to evaluate the effects of trace mineral supplementation on traditional and novel measures of bull fertility. In Experiment 1, 37 mature bulls received one of three dietary supplements daily for 71 d: 1) Supplement without Cu, Zn, and Mn (CON); 2) Supplement with Cu, Zn, and Mn sulfate (SULF); and 3) Supplement with basic Cu chloride, and Zn and Mn hydroxychloride (CHLR). In Experiment 2, 128 Angus or Angus-Hereford bull calves were maintained on a growing diet for 75 d (year 1) or 119 d (year 2) in Calan gate equipped pens without mineral supplementation.

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The focus of gastro-intestinal parasite control in the sheep industry is increasingly on finding a balance between maintaining productivity of the flock whilst minimising selection for anthelmintic resistance to preserve anthelmintic efficacy for the future. Periparturient ewes represent the major source of gastro-intestinal parasites for growing lambs and are therefore a priority for parasite control. This study examines the impact on ewe faecal egg counts (FECs), lamb FECs, lamb daily live weight gains (DLWGs) and pasture larval counts of treating groups of ewes two weeks prior to lambing with either, a long-acting moxidectin treatment, short-acting doramectin or control.

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Regioselective 1,1',3,3'-tetrazincation [C-H to C-Zn(Bu)] of ferrocene has been achieved by reaction of a fourfold excess of di--butylzinc (BuZn) with sodium 2,2,6,6-tetramethylpiperidide (NaTMP) in hexane solution manifested in the trimetallic iron-sodium-zinc complex [Na(TMP)Zn(Bu){(CH)Fe}], . X-ray crystallographic studies supported by DFT modelling reveal the structure to be an open inverse crown in which two [Na(TMP)Zn(Bu)Na(TMP)Zn(Bu)] cationic units surround a {(CH)Fe} tetraanion. Detailed CD NMR studies have assigned the plethora of H and C chemical shifts of this complex.

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The Protein Data Bank in Europe (PDBe), a founding member of the Worldwide Protein Data Bank (wwPDB), actively participates in the deposition, curation, validation, archiving and dissemination of macromolecular structure data. PDBe supports diverse research communities in their use of macromolecular structures by enriching the PDB data and by providing advanced tools and services for effective data access, visualization and analysis. This paper details the enrichment of data at PDBe, including mapping of RNA structures to Rfam, and identification of molecules that act as cofactors.

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Article Synopsis
  • Researchers developed new magnesium complexes using anionic N-heterocyclic carbenes (NHCs) through combined sodium and magnesium interactions.
  • A unique compound was created, revealing unexpected reactivity patterns, like forming an adduct rather than breaking down a specific carbene.
  • The complexes demonstrated the ability to transfer their NHC ligands to gold fragments, leading to new compounds with distinct structural properties.
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The Protein Data Bank in Europe (PDBe, pdbe.org) is actively engaged in the deposition, annotation, remediation, enrichment and dissemination of macromolecular structure data. This paper describes new developments and improvements at PDBe addressing three challenging areas: data enrichment, data dissemination and functional reusability.

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OneDep, a unified system for deposition, biocuration, and validation of experimentally determined structures of biological macromolecules to the PDB archive, has been developed as a global collaboration by the worldwide PDB (wwPDB) partners. This new system was designed to ensure that the wwPDB could meet the evolving archiving requirements of the scientific community over the coming decades. OneDep unifies deposition, biocuration, and validation pipelines across all wwPDB, EMDB, and BMRB deposition sites with improved focus on data quality and completeness in these archives, while supporting growth in the number of depositions and increases in their average size and complexity.

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After isolating an unusual binuclear, but monosolvated NaHMDS complex [{(R,R)-TMCDA}·(NaHMDS)] which polymerises via intermolecular electrostatic NaMe interactions, further (R,R)-TMCDA was added to produce the discrete binuclear amide [{κ-(R,R)-TMCDA}·(NaHMDS){κ-(R,R)-TMCDA}], whose salient feature is the unique monodentate coordination of one of the chiral diamine ligands.

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This study reports the use of the trisalkylgallium GaR (R=CH SiMe ), containing sterically demanding monosilyl groups, as an effective Lewis-acid component for frustrated Lewis pair activation of carbonyl compounds, when combined with the bulky N-heterocyclic carbene 1,3-bis(tert-butyl)imidazol-2-ylidene (ItBu) or 1,3-bis(tert-butyl)imidazolin-2-ylidene (SItBu). The reduction of aldehydes can be achieved by insertion into the C=O functionality at the C2 (so-called normal) position of the carbene affording zwitterionic products [ItBuCH OGaR ] (1) or [ItBuCH(p-Br-C H )OGaR ] (2), or alternatively, at its abnormal (C4) site yielding [aItBuCH(p-Br-C H )OGaR ] (3). As evidence of the cooperative behaviour of both components, ItBu and GaR , neither of them alone are able to activate any of the carbonyl-containing substrates included in this study NMR spectroscopic studies of the new compounds point to complex equilibria involving the formation of kinetic and thermodynamic species as implicated through DFT calculations.

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In the chlorophyll (Chl) biosynthesis pathway the formation of protochlorophyllide is catalyzed by Mg-protoporphyrin IX methyl ester (MgPME) cyclase. The Ycf54 protein was recently shown to form a complex with another component of the oxidative cyclase, Sll1214 (CycI), and partial inactivation of the ycf54 gene leads to Chl deficiency in cyanobacteria and plants. The exact function of the Ycf54 is not known, however, and further progress depends on construction and characterization of a mutant cyanobacterial strain with a fully inactivated ycf54 gene.

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Article Synopsis
  • The study investigates the reactivity of sodium butyl-magnesiate supported by a bulky chelating ligand towards Quinoxaline, revealing its capacity to promote single-electron transfer (SET) processes.
  • The reaction results in the formation of a complex containing two quinoxalyl radical anions stabilized within a dimeric framework, with structural insights obtained through NMR, EPR, and DFT calculations.
  • Further experiments show that different ligands influence the reactivity, with a modification of the original reagent leading to selective reactions with Quinoxaline, indicating the importance of the steric stabilizer for effective reduction.
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The Protein Data Bank in Europe (http://pdbe.org) accepts and annotates depositions of macromolecular structure data in the PDB and EMDB archives and enriches, integrates and disseminates structural information in a variety of ways. The PDBe website has been redesigned based on an analysis of user requirements, and now offers intuitive access to improved and value-added macromolecular structure information.

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  • This study focuses on creating new gallium (Ga) complexes with neutral or anionic N-heterocyclic carbene (NHC) ligands, specifically using the unsaturated carbene IPr.
  • It explores how different methods of combining organometallic reagents lead to the formation of unique gallate species and novel complexes, highlighting the coordination behavior of the ligands.
  • By using NMR spectroscopy and DFT calculations, the research reveals important insights about the transformation mechanisms of these complexes, emphasizing the role of solvent and steric factors in stabilizing various structural forms.
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  • The study investigates the rarely characterized 1-lithio-2-alkyl-1,2-dihydropyridines, which are intermediates in addition reactions involving alkyllithiums and pyridine.
  • By using a specific 1:1 ratio of alkyllithium to pyridine and tridentate donors, the researchers successfully stabilized and crystallized a complex with a tert-butyl group.
  • The research highlights the importance of stoichiometry, illustrating that altering ratios in reactions can lead to different products, including the hydrolithiation of pyridine by kinetic intermediates.
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Previously it was reported that activation of (t)Bu2Zn by [(TMEDA)Na(μ-dpa)]2 led to tert-butylation of benzophenone at the challenging para-position, where the sodium amide functions as a metalloligand towards (t)Bu2Zn manifested in crystalline [{(TMEDA)Na(dpa)}2Zn(t)Bu2] (TMEDA is N,N,N',N'-tetramethylethylenediamine, dpa is 2,2'-dipyridylamide). Here we find altering the Lewis donor or alkali metal within the metalloligand dictates the reaction outcome, exhibiting a strong influence on alkylation yields and reaction selectivity. Varying the former led to the synthesis of three novel complexes, [(PMDETA)Na(dpa)]2, [(TMDAE)Na(dpa)]2, and [(H6-TREN)Na(dpa)], characterised through combined structural, spectroscopic and theoretical studies [where PMDETA is N,N,N',N'',N''-pentamethyldiethylenetriamine, TMDAE is N,N,N',N'-tetramethyldiaminoethylether and H6-TREN is N',N'-bis(2-aminoethyl)ethane-1,2-diamine].

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  • Researchers created a series of alkali-metal zincates by mixing zinc and alkali-metal compounds in hexane, resulting in new complex structures.
  • X-ray studies show different 3D and 2D arrangements of these compounds, with lithium forming a linear chain and sodium and potassium forming more complex networks.
  • Solution studies indicate that these zincates exist as ion-pair species and can be transformed into simpler monomeric forms by adding specific ligands.
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  • The study examines the reactivity of a specific sodium butylmagnesiate reagent, revealing its effectiveness in facilitating direct magnesium-hydrogen exchange reactions with various amines and heterocycles.
  • It demonstrates that this bimetallic base can convert N-methylbenzimidazole into a α-metallated intermediate under mild conditions, while also highlighting its polybasic properties through reactions with different amines to form several new crystalline compounds.
  • Crystallographic and NMR data suggest that the metallated carbon in the derived compounds exhibits significant carbenic character, and the results indicate distinct structural differences between similar heteroleptic bis(amido) products formed during these reactions.
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The series of alkali-metal (Li, Na, K) complexes of the substituted benzyl anion 3,5-dimethylbenzyl (Me2C6H3CH2(-)) derived from 1,3,5-trimethylbenzene (mesitylene) have been coerced into monomeric forms by supporting them with the tripodal tetradentate Lewis donor tris(N,N-dimethyl-2-aminoethyl)amine, [N(CH2CH2NMe2)3, Me6TREN]. Molecular structure analysis by X-ray crystallography establishes that the cation-anion interaction varies as a function of the alkali-metal, with the carbanion binding to lithium mainly in a σ fashion, to potassium mainly in a π fashion, with the interaction toward sodium being intermediate between these two extremes. This distinction is due to the heavier alkali-metal forcing and using the delocalization of negative charge into the aromatic ring to gain a higher coordination number in accordance with its size.

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Amyloid is identified microscopically as an amorphous extracellular hyaline material that exhibits "apple-green" birefringence with Congo red stains. Amyloid is not a chemically distinct entity, and currently available molecular methods are capable of identifying over 20 amyloidogenic precursor proteins. Some of the more common diseases associated with amyloidosis include plasma cell dyscrasias, chronic inflammatory disorders, hereditary-familial mutations involving transthyretin, Alzheimer's disease, and so-called "senile" or age-related amyloidosis.

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  • Recent advancements in metallation chemistry focus on replacing the expensive 2,2,6,6-tetramethylpiperidide (TMP) with the cheaper alternative cis-2,6-dimethylpiperidide (cis-DMP) for mixed-metal bases, leading to the development of cis-DMP zincate chemistry.
  • A new compound, lithium diethylzincate, was synthesized and characterized using NMR and X-ray crystallography, demonstrating a dinuclear arrangement, and was found to exhibit superior deprotonative reactivity compared to the previously studied di-tert-butylzincate.
  • The cis-DMP-based system yielded better
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Soft scorpionates have thus far been seen mainly as a family of ligands. Their chemistry is extended here to the production of novel cationic macrocycles using dihaloalkanes. By replacing the dihaloalkanes with mild oxidising agents (NO(+), I2) we obtain two unique polycyclic heterocycles.

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