School of Chemistry - Research Publications
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ItemCellular Up-regulation of Nedd4 Family Interacting Protein 1 (Ndfip1) using Low Levels of Bioactive Cobalt Complexes(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2011-03-11)The delivery of metal ions using cell membrane-permeable metal complexes represents a method for activating cellular pathways. Here, we report the synthesis and characterization of new [Co(III)(salen)(acac)] complexes capable of up-regulating the ubiquitin ligase adaptor protein Ndfip1. Ndfip1 is a neuroprotective protein that is up-regulated in the brain after injury and functions in combination with Nedd4 ligases to ubiquitinate harmful proteins for removal. We previously showed that Ndfip1 can be increased in human neurons using CoCl(2) that is toxic at high concentration. Here we demonstrate a similar effect can be achieved by low concentrations of synthetic Co(III) complexes that are non-toxic and designed to be activated following cellular entry. Activation is achieved by intracellular reduction of Co(III) to Co(II) leading to release of Co(II) ions for Ndfip1 up-regulation. The cellular benefit of Ndfip1 up-regulation by Co(III) complexes includes demonstrable protection against cell death in SH-SY5Y cells during stress. In vivo, focal delivery of Co(III) complexes into the adult mouse brain was observed to up-regulate Ndfip1 in neurons. These results demonstrate that a cellular response pathway can be advantageously manipulated by chemical modification of metal complexes, and represents a significant step of harnessing low concentration metal complexes for therapeutic benefit.
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ItemTriggered and Tunable Hydrogen Sulfide Release from Photogenerated Thiobenzaldehydes(WILEY-V C H VERLAG GMBH, 2017-08-22)Hydrogen sulfide (H2 S) has been identified as an important cell-signaling mediator and has a number of biological functions, such as vascular smooth muscle relaxation, neurotransmission, and regulation of inflammation. A facile and versatile approach for H2 S production initiated by light irradiation and controlled by reaction with an amine or an amino acid was developed. The donor was synthesized in a one-pot reaction, and simple crystallization led to a yield of approximately 90 %. The synthetic strategy is scalable and versatile, and the H2 S donors can be expressed ina number of different molecular and macromolecular forms, including crystalline small-molecule compounds, water-soluble polymers, polystyrene films, and hydrogels. The H2 S donors based on polystyrene film and hydrogel were used as cell-culture scaffolds. The H2 S donor based on water-soluble polymer was applied in photocontrolled inhibition of P-selectin expression on human platelets and subsequent regulation of platelet aggregation. This study provides the simplest controllable H2 S source to study its biological functions. The developed materials are also new therapeutic platforms to deliver H2 S, as there is no accumulation of toxic byproducts, and the donor materials from polystyrene films and hydrogels can be readily removed after releasing H2 S.
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ItemGuest‐induced Assembly of Bis(thiosemicarbazonato) Zinc(II) Coordination Nanotubes(Wiley, 2017-07-10)Abstract A ZnII complex of the dianionic tetradentate ligand formed by deprotonation of glyoxal‐bis(4‐phenyl‐3‐thiosemicarbazone) (H2gtsp) is a [3+3] trinuclear triangular prism. Recrystallization of this complex in the presence of either CO2, CS2, or CH3CN leads to the formation of [4+4] open‐ended charge‐neutral tetranuclear coordination nanotubes, approximately 2 nm in length and with internal dimensions large enough to accommodate linear guest molecules, which serve to template their formation. Upon removal of the templating molecules the nanotubes demonstrated reversible sorption of CO2 with an isosteric enthalpy of sorption of 28 kJ mol−1 at low loading.
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ItemGuest-induced Assembly of Bis(thiosemicarbazonato) Zinc(II) Coordination Nanotubes(Wiley, 2017-07-10)A ZnII complex of the dianionic tetradentate ligand formed by deprotonation of glyoxal‐bis(4‐phenyl‐3‐thiosemicarbazone) (H2gtsp) is a [3+3] trinuclear triangular prism. Recrystallization of this complex in the presence of either CO2, CS2, or CH3CN leads to the formation of [4+4] open‐ended charge‐neutral tetranuclear coordination nanotubes, approximately 2 nm in length and with internal dimensions large enough to accommodate linear guest molecules, which serve to template their formation. Upon removal of the templating molecules the nanotubes demonstrated reversible sorption of CO2 with an isosteric enthalpy of sorption of 28 kJ mol−1 at low loading.
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ItemDihydro-β-agarofurans from the Australian Endemic Rainforest Plant Denhamia pittosporoides Inhibit Leucine Transport in Prostate Cancer Cells(WILEY-V C H VERLAG GMBH, 2016-12)Abstract Two previously unknown dihydro‐β‐agarofuran sesquiterpenoids, denhaminol I (1) and denhaminol J (2), together with four related and known metabolites, 1α,2α,6β,15‐tetraacetoxy‐9α‐benzoyloxy‐8‐oxodihydro‐β‐agarofuran (3), wilforsinine F (4), 1α,2α,6β,8α,15‐pentaacetoxy‐9α‐benzoyloxydihydro‐β‐agarofuran (5), and 1α,2α,6β,15‐tetraacetoxy‐9β‐benzoyloxydihydro‐β‐agarofuran (6), were isolated from the leaves of an Australian rainforest plant, Denhamia pittosporoides. The structures of compounds 1 and 2 were determined by analysis of their 1D/2D NMR and MS data. The absolute configuration of compound 1 was established by single‐crystal X‐ray diffraction analysis. Compounds 1 and 4 were shown to inhibit leucine transport in the human prostate cancer cell line LNCaP, with IC50 values of 51.5 and 95.5 μm, respectively. Both compounds 1 and 4 were more potent than the l‐type amino acid transporter (LAT) family inhibitor 2‐aminobicyclo[2.2.1]‐heptane‐2‐carboxylic acid (BCH). This is the first report of dihydro‐β‐agarofurans from D. pittosporoides.
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ItemFluorine-18 radiolabeling of a nitrophenyl sulfoxide and its evaluation in an SK-RC-52 model of tumor hypoxia(WILEY-BLACKWELL, 2016-08)The significance of imaging hypoxia with the positron emission tomography ligand [(18) F]FMISO has been demonstrated in a variety of cancers. However, the slow kinetics of [(18) F]FMISO require a 2-h delay between tracer administration and patient scanning. Labeled chloroethyl sulfoxides have shown faster kinetics and higher contrast than [(18) F]FMISO in a rat model of ischemic stroke. However, these nitrogen mustard analogues are unsuitable for routine production and use in humans. Here, we report on the synthesis and in vitro and in vivo evaluation of a novel sulfoxide, which contains an ester moiety for hydrolysis and subsequent trapping in hypoxic cells. Non-decay corrected yields of radioactivity were 1.18 ± 0.24% (n = 27, 2.5 ± 0.5% decay corrected radiochemical yield) based on K[(18) F]F. The radiotracer did not show any defluorination and did not undergo metabolism in an in vitro assay using S9 liver fractions. Imaging studies using an SK-RC-52 tumor model in BALB/c nude mice have revealed that [(18) F]1 is retained in hypoxic tumors and has similar hypoxia selectivity to [(18) F]FMISO. Because of a three times faster clearance rate than [(18) F]FMISO from normoxic tissue, [(18) F]1 has emerged as a promising new radiotracer for hypoxia imaging.
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ItemSynthesis of Homochiral Co-III- and Mn-IV-[2.2]Paracyclophane Schiff Base Complexes with Predetermined Chirality at the Metal Centre(WILEY-V C H VERLAG GMBH, 2016-08-01)The planar chiral Schiff base ligand 2, derived from (Rp)‐5‐formyl‐4‐hydroxy‐[2.2]paracyclophane (FHPC) (1), was utilised to form a Λ‐CoIII cis‐β‐octahedral metal complex 3 with complete control of the metal‐centred chirality. In addition, a di‐µ‐oxo Λ,Λ‐MnIV complex 4 was synthesised with control of both metal‐centred and (P)‐helical chirality.
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ItemTetraphenylethene 9,10-Diphenylanthracene Derivatives - Synthesis and Photophysical Properties(WILEY-V C H VERLAG GMBH, 2019-06)A series of tetraphenylethene 9,10-diphenylanthracene (TPE-DPA) derivatives have been synthesized, and their photophysical properties studied. Photoluminescence measurements in PMMA, neat films and nanoparticle dispersions reveal that different aggregation states are formed, which leads to different photophysical behavior. The triplet excited state properties were studied using Pt(II) octaethylporphyrin (PtOEP) as triplet sensitizer. Upconverted emission from the DPA moiety is observed in nanoparticle dispersions of each derivative. A higher upconverted emission intensity is observed in aerated (compared to deaerated) solutions of the derivatives following irradiation, which is attributed to oxidation of the TPE moiety. These results provide valuable insight for the design of AIE luminogens for triplet-triplet annihilation upconversion (TTA-UC).
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ItemSonochemical synthesis of a two-dimensional supramolecular polymer with nanoporous morphology, linear thallophilic and covalent hydrogen-bonding interactions(WILEY, 2019-03)A new thallium‐based supramolecular polymer [Tl(μ3–3‐HClb)(μ3–3‐Clb)]n (1), (3‐HClb = 3‐chloroperbenzoic acid), has been synthesized and structurally characterized by single crystal X‐ray crystallography. It has a two‐dimensional structure with linear thallophilic and covalent hydrogen‐bonding interactions. In order to evaluate the effects of concentration, ultrasonic irradiation and type of solvents on structure, morphology and thermal behavior of 1, some experiments were designed, and eight samples of 1 were synthesized under different conditions. These samples were characterized by IR spectroscopy, thermogravimetric and differential thermal analyses, X‐ray powder diffraction and scanning electron microscopy.
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ItemA new potassium-based coordination polymer with hydrogen bonding and zigzag metallophilic interactions(WILEY, 2018-12)A new potassium‐based coordination polymer [K (μ7‐HTar)]n (1), (H2Tar = (+)‐tartaric acid), has been synthesized and structurally characterized by single crystal X‐ray crystallography. It has a three‐dimensional structure with zigzag K···K metallophilic interactions. Also widespread hydrogen bonding network in three‐dimensional structure of 1 was observed. In order to evaluation the effects of concentration, ultrasonic irradiation and type of the solvents on morphology and thermal behavior of 1, some experiments were designed and six samples of 1 were synthesized under different conditions. These samples were characterized by IR spectroscopy, thermo gravimetric and differential thermal analyses (TG‐DTA), X‐ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM).