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Browsing Faculty & Staff Research by Subject "Chemistry"
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Item A uranium atlas, from 365 to 505 nm(Elsevier, 2020-03-02) Ross, Amanda J.; Crozet, Patricia; Adam, Allan G.; Tokaryk, Dennis W.A Fourier-transform spectrum of the emission from a commercial uranium hollow-cathode lamp 19,800–27,400 cm−1 is proposed, in ascii format, as a possible aid to calibration of laser excitation spectra.Item An alternative approach to interferogram collection and processing for a vintage Bomem DA3 Fourier transform spectrometer(Elsevier, 2019-08-12) Guislain, B.G.; Harvey, R.A.R; Tokaryk, D.W.; Ross, A.J.; Crozet, P.; Adam, A.G.We describe a new way of collecting data from Bomem DA3 Fourier transform spectrometers, bypassing the original computers used by these instruments, which are obsolete and more prone to failure than other parts of the system. We collect the interferogram, helium-neon reference laser, and a trigger marking zero path difference with a modern computer as a function of time at a high data rate, as opposed to as a function of position along the scanning arm of the interferometer. The interferogram is then reconstructed as a function of position (measured in helium-neon fringes) by interpolation. The resulting spectra are at least as good as those obtained from the original data processing methods. This work can be used as a model for reviving other DA3 systems which are in good order with respect to mechanical and electronic components, but with nonfunctional computers, or for collecting and processing data for any other Fourier transform spectrometers.Item Caryophyllene sesquiterpenes from a Chaetomium globosum endophyte of the Canadian Medicinal plant Empetrum nigrum(American Chemical Society, 2023-06-02) Morehouse, Nicholas J.; Clark, Trevor N.; Kerr, Russell G.; Johnson, John A.; Gray, Christopher A.Punctaporonins T (1) and U (2), new caryophyllene sesquiterpenes, were isolated with three known punctaporonins, A (3), B (4), and C (5), from the endophytic fungus Chaetomium globosum (TC2-041). The structures and relative configurations of punctaporonins T and U were elucidated based on a combination of HRESIMS, 1D/2D NMR spectroscopic analysis, and X-ray diffraction analysis whilst their absolute configuration is presumed to be consistent with the co-isolated 3–5 on biogenetic arguments. Compound 1 showed weak inhibitory activity against both Mycobacterium tuberculosis and Staphylococcus aureus.Item Discovery of an isothiazolinone-containing antitubercular natural product Levesquamide(American Chemical Society, 2020-05-04) Liang, Libang; Haltli, Bradley; Marchbank, Douglas H.; Fischer, Maike; Kirby, Christopher W.; Correa, Hebelin; Clark, Trevor N.; Gray, Christopher A.; Kerr, Russell G.Antitubercular agent levesquamide is a new polyketide-nonribosomal peptide (PK-NRP) hybrid marine natural product isolated from Streptomyces sp. RKND-216. The structure contains a rare isothiazolinone moiety which has only been reported in collismycin SN. Structure elucidation by NMR spectroscopy was a significant challenge due to a deficiency of protons in this aromatic moiety. Therefore, the genome of Streptomyces sp. RKND-216 was sequenced to identify the levesquamide biosynthetic gene cluster (BGC). Analysis of the BGC provided structural insights and guided stable-isotope labeling experiments, which led to the assignment of the fused pyridine-isothiazolinone moiety. The BGC and the labeling experiments provide further insights into the biosynthetic origin of isothiazolinones. Levesquamide exhibited antimicrobial activity in the microplate alamarBlue assay (MABA) and low oxygen recovery assay (LORA) against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) values of 9.65 and 22.28 µM, respectively. Similar activity was exhibited against rifampicin- and isoniazid-resistant M. tuberculosis strains with MIC values of 9.46 and 9.90 µM, respectively. This result suggests levesquamide has a different mode of action against M. tuberculosiscompared to the two first-line antitubercular drugs rifampicin and isoniazid. Furthermore, levesquamide shows no cytotoxicity against the Vero cell line, suggesting it may have a useful therapeutic window.Item High-resolution spectroscopy of the [18.4]2.5 – X2Δ5/2 transition of ruthenium monoboride (RuB)(Elsevier, 2020-06-30) Dore, J.M.; Adam, A.G.; Linton, C.; Tokaryk, D.W.Laser-induced fluorescence spectra of the (0, 0), (1, 0) and (0, 1) bands of the [18.4]2.5 – X2Δ5/2 transition have been recorded at high-resolution for several isotopologues of ruthenium monoboride (RuB). We report band origins and rotational parameters for 12 of the 14 possible isotopologues (7 for each of Ru11B and Ru10B) as well as hyperfine parameters of 99RuB and 101RuB. An anomalous isotope shift in the (0, 0) and (0, 1) bands indicates a weak perturbation in the [18.4]2.5 v = 0 vibrational level. The observed hyperfine structure is mainly due to the nuclear spin (I = 5/2) of the two Ru isotopes. Hyperfine structure due to the 11B and 10B isotopes was not resolved and resulted in, at most, a slight broadening of the lines. The magnetic hyperfine parameters help to confirm the (11σ)2(5π)4(2δ)3 configuration of the ground electronic state and provide insight into the configuration of the excited states.Item Hyperfine Analysis of the (2, 0) [18.3]3-X3Δ3 Transition of Cobalt Monoboride(Elsevier, 2019) Dore, J. M.; Adam, A. G.; Tokaryk, D. W.; Linton, C.High-resolution laser-induced fluorescence spectra of the (2, 0) [18.3]3-X3Δ3 transition of cobalt monoboride (CoB) have been recorded. We report updated rotational parameters for both the [18.3]3 (v′ = 2) and X3Δ3 (v″ = 0) states of Co11B, as well as newly determined hyperfine interaction parameters. The observed hyperfine splitting is mainly due to the nuclear spin of 59Co (I = 7/2, μ/μN = 4.627); the 11B (I = 3/2, μ/μN = 2.689) interaction only results in broadening of the individual hyperfine transitions. The magnetic hyperfine constants help confirm the ground state electronic configuration, (8σ)2(3π)4(1δ)3(9σ)1, and provide more insight into the configurational mixing in the excited state.Item Influencing the Optoelectronic Properties of a Heteroleptic Iridium Complex by Second-Sphere H-Bonding Interactions(American Chemical Society, July 3, 2018) Balónová, Barbora; Rota Martir, Diego; Clark, Ewan, R.; Shepherd, Helena, J.; Zysman-Colman, Eli; Blight, Barry, A.The use of a new second-sphere coordination methodology for emission color tuning of iridium complexes is presented. We demonstrate that a complimentary H-bonding guest molecule binding through contiguous triple H-bonding interactions can induce a shift in the emission of the iridium complex from green to blue without the need to alter the ligand structure around the metal centre, while simultaneously increasing the photoluminescence quantum yield in solution. The association constant for this host-guest interaction was determined to be Ka = 4.3 x 103 M-1 in a solution of 2% dimethylsulfoxide in chloroform by UV-Vis titration analysis and the impact of the hydrogen bonding interaction further probed by photoluminescence, electrochemical, and computational methods. Our findings suggest that directed self-assemblies are an effective approach to influencing emission properties of phosphorescent iridium (III) complexes.Item Isolation of an antimicrobial racemic phenalenone derivative from a marine-derived Penicillium sp. fungus(Canadian Science Publishing, 2023-10-30) Morehouse, Nicholas J.; Graham, Kelsie M.; Cox, Samantha L.; Johnson, John A.; Gray, Christopher A.A new phenalenone derivative, 2,4,6,9-tetrahydroxy-7-methyl-2-prenyl-1H-phenalene 1,3(2H)-dione (1), was isolated from the ethyl acetate extract of a marine derived Penicillium sp. fungus that exhibited a unique antimicrobial activity profile. The planar structure of 1 was determined through a combination of 1D and 2D NMR experiments, and circular dichroism and polarimetry indicated that it was isolated as a racemic mixture of enantiomers. The antimicrobial activity of 1 was assessed against a panel of Gram-positive and Gram-negative bacteria and fungal strains and it was found to selectively inhibit the growth of Staphylococcus aureus and Mycobacterium tuberculosis. Keywords: Phenalenone, Penicillium, Natural product, AntimicrobialItem Thioarylmaleimides: accessible, tunable, and strongly emissive building blocks(Royal Society of Chemistry, 2019) Price, Jayden; Albright, Emily; Decken, Andreas; Eisler, SaraA series of thioarylmaleimides was synthesized to investigate how variation of the thioaryl group can be used to control absorption and emission properties in solution and in the solid-state. Fine-tuning of the photochemical properties was found to be possible using this strategy, and a rainbow of colours and emission wavelengths are accessible in a single step from commercially available compounds.Item Tolypocaibols: Antibacterial lipopeptaibols from a Tolypocladium sp. endophyte of the marine macroalga Spongomorpha arcta(American Chemical Society, 2023-06-14) Morehouse, Nicholas J.; Flewelling, Andrew J.; Liu, Dennis Y.; Cavanagh, Hannah; Linington, Roger G.; Johnson, John A.; Gray, Christopher A.Two new lipopeptaibols, tolypocaibols A (1) and B (2), and the mixed NRPS-polyketide shikimate natural product maximiscin [(P/M)-3)] were isolated from a Tolypocladium sp. fungal endophyte of the marine alga Spongomorpha arcta. Analysis of NMR and mass spectrometry data revealed the amino acid sequences of the lipopeptaibols, which both comprise 11 residues with a valinol C-terminus and a decanoyl acyl chain at the N-terminus. The configuration of the amino acids was determined by Marfey’s analysis. Tolypocaibols A (1) and B (2) showed moderate, selective inhibition against Gram-positive and acid-fast strains, while maximiscin [(P/M)-3)] showed moderate, broad-spectrum inhibition.