ORCID Profile
0000-0003-0436-2044
Current Organisation
Queensland University of Technology
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Biological And Medical Chemistry | Macromolecular and Materials Chemistry | Biochemistry and Cell Biology | Nanochemistry and Supramolecular Chemistry | Chemical Characterisation of Materials | Biotechnology Not Elsewhere Classified | Free Radical Chemistry | Physical Chemistry Of Macromolecules | Instruments And Techniques | Neurosciences Not Elsewhere Classified | Organic Chemistry | Biologically Active Molecules | Other Physical Sciences | Materials engineering | Biochemistry And Cell Biology Not Elsewhere Classified | Structural Chemistry | Synthesis Of Macromolecules | Organic Chemical Synthesis | Atmospheric Sciences | Organic Chemical Synthesis | Polymerisation Mechanisms | Characterisation Of Macromolecules | Therapies And Therapeutic Technology | Organic semiconductors | Polymers and plastics | Atmospheric Aerosols | Nanoelectronics | Biological Sciences Not Elsewhere Classified | Medical Biochemistry: Proteins And Peptides | Cell Metabolism | Protein Targeting And Signal Transduction | Organic Chemistry Not Elsewhere Classified | Membrane Biology | Enzymes | Other Medical and Health Sciences | Analytical Chemistry | Bioinorganic Chemistry | Characterisation of Biological Macromolecules | Separation Science | Nutrition And Dietetics | Medicinal and Biomolecular Chemistry | Inorganic Chemistry | Physical Chemistry (Incl. Structural) | Supramolecular Chemistry | Neurology And Neuromuscular Diseases | Cell Development, Proliferation and Death
ANZSRC Socio-Economic Objective (SEO)
Biological sciences | Chemical sciences | Plastics in primary forms | Expanding Knowledge in the Chemical Sciences | Land and water management | Treatments (e.g. chemicals, antibiotics) | Industrial instrumentation | Cancer and related disorders | Expanding Knowledge in the Biological Sciences | Food safety | Earth sciences | Physical sciences | Diagnostics | Other environmental aspects | Organs, diseases and abnormal conditions not elsewhere classified | Paints | Urban and Industrial Air Quality | Plastic products (incl. Construction materials) | Nervous system and disorders | Inherited diseases (incl. gene therapy) | Polymeric materials (e.g. paints) | Industrial Chemicals and Related Products not elsewhere classified |
Related Links
Publications
Pro-fluorescent mitochondria-targeted real-time responsive redox probes synthesised from carboxy isoindoline nitroxides: Sensitive probes of mitochondrial redox status in cells
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.FREERADBIOMED.2018.03.008
Abstract: Here we describe new fluorescent probes based on fluorescein and rhodamine that provide reversible, real-time insight into cellular redox status. The new probes incorporate bio-imaging relevant fluorophores derived from fluorescein and rhodamine linked with stable nitroxide radicals such that they cannot be cleaved, either spontaneously or enzymatically by cellular processes. Overall fluorescence emission is determined by reversible reduction and oxidation, hence the steady state emission intensity reflects the balance between redox potentials of critical redox couples within the cell. The permanent positive charge on the rhodamine-based probes leads to their rapid localisation within mitochondria in cells. Reduction and oxidation also leads to marked changes in the fluorophore lifetime, enabling monitoring by fluorescence lifetime imaging microscopy. Finally, we demonstrate that administration of a methyl ester version of the rhodamine-based probe can be used at concentrations as low as 5 nM to generate a readily detected response to redox stress within cells as analysed by flow cytometry.
Factors influencing the photocatalytic hydroamination of alkynes with anilines catalyzed by supported gold nanoparticles under visible light irradiation
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA01518B
Abstract: The hydroamination of alkynes with amines is successfully driven by visible-light when using AuNPs on metal oxide supports as plasmonic photocatalysts.
Synthesis and evaluation of new N6-substituted adenosine-5′-N-methylcarboxamides as A3 adenosine receptor agonists
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.BMC.2010.03.047
Abstract: A number of N(6)-substituted adenosine-5'-N-methylcarboxamides were synthesised and their pharmacology, in terms of their receptor affinity, selectivity and cardioprotective effects, were explored. The first series of compounds, 4a-4f and 5a-5f, showed modest receptor affinity for the A(3)AR with K(i) values in the low to mid muM range. However, the incorporation of a 4-(2-aminoethyl)-2,6-di-tert-butylphenol group in the N(6)-position (in compounds 4g and 5g) significantly improved the affinity with K(i) values of 30 and 9 nM, respectively. Improvements in affinity, as well as selectivity were seen when a functionalized linker was introduced. The N(6)-phenyl series, compounds 7a-7d, demonstrated low to mid nanomolar receptor affinities (K(i)=2.3-45.0 nM), with 7b displaying 109-fold selectivity for the A(3)AR (vs A(1)). The N(6)-benzyl series 9a-9c also proved to be potent and selective A(3)AR agonists and the longer chain length linker 13 was tolerated at the A(3)AR without abrogation of affinity or selectivity. Cardioprotection was demonstrated by a simulated ischaemia cell culture assay, whereby 7b, 7c, 9a, 9b and 9c all showed cardioprotective effects at 100 nM comparable or better than the benchmark A(3)AR agonist IB-MECA, but which were indistinguishable by statistical analysis. For ex le, compound 9c reduced cell death by 68.0+/-3.6%.
Electrospray mass spectrometry of stable iminyl nitroxide and nitronyl nitroxide free radicals
Publisher: Wiley
Date: 13-08-2002
DOI: 10.1002/JMS.339
Abstract: Electrospray ionization (ESI) mass spectra have been recorded for a range of substituted nitronyl nitroxide and iminyl nitroxide monoradicals and biradicals. Secondary species formed in the ESI source were observed as the dominant ions in both the iminyl nitroxide and nitronyl nitroxide spectra. Daughter ion spectrometry was used to establish fragmentation mechanisms for the nitronyl nitroxide and iminyl nitroxide moieties as well as the secondary species under ESI conditions.
The Use of a Nitroxide Probe in DMSO to Capture Free Radicals in Particulate Pollution
Publisher: Wiley
Date: 11-09-2012
The challenges in lifetime prediction of oxodegradable polyolefin and biodegradable polymer films
Publisher: Elsevier BV
Date: 11-2017
Oxidative potential of gas phase combustion emissions - An underestimated and potentially harmful component of air pollution from combustion processes
Publisher: Elsevier BV
Date: 06-2017
The impact of carboxy nitroxide antioxidants on irradiated ataxia telangiectasia cells
Publisher: Elsevier BV
Date: 10-2004
Stable Copper Nanoparticle Photocatalysts for Selective Epoxidation of Alkenes with Visible Light
Publisher: American Chemical Society (ACS)
Date: 30-06-2017
Back matter
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2SC90049A
Selective deoxygenation of carbonyl groups at room temperature and atmospheric hydrogen pressure over nitrogen-doped carbon supported Pd catalyst
Publisher: Elsevier BV
Date: 12-2018
Polycarbonate microspheres containing mitomycin C and magnetic powders as potential hepatic carcinoma therapeutics
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.COLSURFB.2011.02.016
Abstract: The polycarbonate copolymer poly(trimethylene carbonate-co-5,5-dimethyl trimethylene carbonate) (P(TMC-co-DTC)) was synthesized by the polymerization of trimethylene carbonate (TMC) and 5,5-dimethyl trimethylene carbonate (DTC) using tin (II) 2-ethylhexanoate [Sn(Oct)(2)] as a catalyst. In vitro degradation tests indicated this polycarbonate copolymer degraded slowly in phosphate buffer saline solution (PBS, 0.1 mol/L, at 37°C). Magnetic polymer microspheres (MMC-PC-M) generated from the P(TMC-co-DTC) copolymer and containing Fe(3)O(4) magnetic ultrafine powders and an anticancer drug, mitomycin C (MMC) were prepared by a solvent evaporation technique. These anticancer magnetic polycarbonate microspheres showed strong magnetic responsiveness and high MMC loading capacity. In vitro drug release studies indicated that these microspheres sustained steady release rates of MMC in PBS. In vitro cytotoxicity assays demonstrated the microspheres were strongly inhibitory to human hepatic carcinoma (Bel-7204) cells. In vivo site-specific therapy in nude mice with human hepatic carcinoma indicated that the microspheres possessed markedly high antitumor activity against human hepatic carcinoma (Bel-7204).
Current and potential therapeutic strategies for the treatment of ataxia-telangiectasia
Publisher: Oxford University Press (OUP)
Date: 06-02-2007
DOI: 10.1093/BMB/LDM012
Abstract: Ataxia-telangiectasia (A-T) is a rare autosomal recessive genetic disorder characterized by progressive neurodegeneration, a high risk of cancer and immunodeficiency. These patients are also hypersensitive to radiotherapy. The gene product defective in this syndrome, ATM (ataxia-telangiectasia mutated), normally recognizes DNA damage and signal to the DNA repair machinery and the cell cycle checkpoints to minimize the risk of genetic damage. No curative strategy for this disease exists. Treatment has focused on slowing the progress of the neurodegeneration devising approaches for the treatment of tumours while minimizing side effects and treatment with immunoglobulin for the immunodeficiency. The most debilitating feature of this disorder is the progressive neurodegeneration due to loss of Purkinje cells in the cerebellum and malfunction of other neuronal cells. Correcting for the loss of Purkinje cells is technically very difficult and would require transplantation of embryonic stem cells. However, since it seems likely that oxidative stress may contribute to the neurodegeneration in A-T, potential therapies based on the use of antioxidants offer some hope. We describe the natural course of disease, some supportive therapeutic approaches already in use and those with potential based on our knowledge of molecular and cellular characteristics of this disorder.
Trapping of Cyclopentanediyl and Trimethylenemethane Triplet Diradicals with the Nitroxide 1,1,3,3-tetramethyl-1,3-dihydroisoindolin-2-yloxyl
Publisher: American Chemical Society (ACS)
Date: 1992
DOI: 10.1021/JO00029A036
Synthesis and Pharmacological Evaluation of Dual Acting Antioxidant A2A Adenosine Receptor Agonists
Publisher: American Chemical Society (ACS)
Date: 29-03-2012
DOI: 10.1021/JM300206U
Abstract: A series of adenosine-5'-N-alkylcarboxamides and N(6)-(2,2-diphenylethyl)adenosine-5'-N-alkylcarboxamides bearing antioxidant moieties in the 2-position were synthesized from the versatile intermediate, O(6)-(benzotriazol-1-yl)-2-fluoro-2',3'-O-isopropylideneinosine-5'-N-alkylcarboxamide (1). These compounds were evaluated as A(2A) adenosine receptor (A(2A)R) agonists in a cAMP accumulation assay, and a number of potent and selective agonists were identified. Three of these compounds were evaluated further in an ischemic injury cell survival assay and a reactive oxygen species (ROS) production assay whereby 15b and 15c were shown to reduce ROS activity and cell death due to ischemia.
Monitoring Free Radical Reactions in Degrading Polymers with a Profluorescent Nitroxide
Publisher: American Chemical Society
Date: 21-12-2007
Synthesis and EPR spin trapping properties of a new isoindole-based nitrone: 1,1,3-trimethylisoindole N-oxide (TMINO)
Publisher: Royal Society of Chemistry (RSC)
Date: 2003
DOI: 10.1039/B300642E
Abstract: Here we describe the synthesis and characterisation of a new isoindole-based nitrone spin trap, 1,1,3-trimethylisoindole N-oxide (TMINO). This nitrone and its radical adducts (isoindoline nitroxides) exhibit enhanced stability with respect to other commonly used spin traps and their adducts. We also report EPR trapping studies of this new nitrone with some carbon- and oxygen-centred radicals including alkyl, aryl, hydroxyl and benzoyloxyl systems. The narrow EPR line-widths and stability of the resulting nitroxide spin adducts allowed the detection of the expected radicals as well as secondary and minor radical components in the reaction mixtures.
Influence of fuel molecular structure on the volatility and oxidative potential of biodiesel particulate matter
Publisher: American Chemical Society (ACS)
Date: 27-10-2014
DOI: 10.1021/ES503160M
Abstract: We have studied the effect of chemical composition of biodiesel fuel on the physical (volatility) and chemical (reactive oxygenated species concentration) properties of nano particles emitted from a modern common-rail diesel engine. Particle emissions from the combustion of four biodiesels with controlled chemical compositions and different varying unsaturation degrees and carbon-chain lengths, together with a commercial diesel, were tested and compared in terms of volatility of particles and the amount of reactive oxygenated species carried by particles. Different blends of biodiesel and petro diesel were tested at several engine loads and speeds. We have observed that more saturated fuels with shorter carbon chain lengths result in lower particle mass but produce particles that are more volatile and also have higher levels of Reactive Oxygen Species. This highlights the importance of taking into account metrics that are relevant from the health effects point of view when assessing emissions from new fuel types.
Spin-coated carbon
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SC51396C
Highly efficient and selective photocatalytic hydroamination of alkynes by supported gold nanoparticles using visible light at ambient temperature
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC38985E
Abstract: The direct hydroamination of alkynes driven by visible light can be achieved in high yield and selectivity at ambient temperature using supported gold nanoparticles (AuNPs) as photocatalysts. Aniline molecules interact with visible light activated AuNPs meanwhile alkynes could be activated at active sites on the support. The findings reveal a new green approach for synthesis of fine organic compounds and provide insight into catalyst design for the activation of C≡C triple bonds and amines.
Concentration and oxidative potential of on-road particle emissions and their relationship with traffic composition: Relevance to exposure assessment
Publisher: Elsevier BV
Date: 11-2012
A Profluorescent Azaphenalene Nitroxide for Nitroxide-Mediated Polymerization
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/CH10404
Abstract: A novel nitroxide‐mediated polymerization (NMP) control agent 1,1,3,3‐tetramethyl‐2,3‐dihydro‐2‐azaphenalen‐2‐yloxyl (TMAO), was used in the free‐radical polymerization of styrene. The conversion of styrene during NMP was studied using FT‐Raman spectroscopy and the effectiveness of TMAO as a NMP control agent was assessed by GPC analysis. Fidelity of the TMAO‐alkoxyamine end‐group on the synthesized polymers was confirmed by GPC, UV‐Vis and fluorescence spectroscopic analyses. Comparison to the well known NMP control agent, TEMPO was made. TMAO showed control of molecular weight approaching that of TEMPO. Attempts to improve the properties of TMAO as an NMP control agent by synthesizing an analogue with bulkier substituents around the nitroxide did not generate the target molecule but demonstrated some of the interesting chemistry of the azaphenalene ring system.
A novel protecting group methodology for syntheses using nitroxides
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC46146G
Abstract: Protecting a nitroxide as the methyl ether is highly effective. It can be de-protected in good yield using a peracid.
Inhibitive action of the octyl esters of 4- and 5-carboxybenzotriazole for copper corrosion in sulphate solutions
Publisher: Elsevier BV
Date: 02-2000
Spin probes for electron paramagnetic resonance imaging
Publisher: Elsevier BV
Date: 12-2008
A novel profluorescent nitroxide as a sensitive probe for the cellular redox environment
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.FREERADBIOMED.2010.03.019
Abstract: Changes to the redox status of biological systems have been implicated in the pathogenesis of a wide variety of disorders. Sensitive quantification of these changes has been developed using a novel fluorescent probe containing a redox-sensitive nitroxide moiety. As well as being able to selectively detect the superoxide radical in vitro, this method can measure overall changes to the cellular redox environment using flow cytometry on the basis of nitroxide reduction. The reversible nature of the probe's detection mechanism offers the unique advantage of being able to monitor redox changes in both oxidizing and reducing directions in real time.
Impact of molecular size on electron spin relaxation rates of nitroxyl radicals in glassy solvents between 100 and 300 K
Publisher: Informa UK Limited
Date: 10-08-2007
Improved synthesis of 'cord factor' analogues
Publisher: Royal Society of Chemistry (RSC)
Date: 1984
DOI: 10.1039/C39840000385
The Synthesis and Physical Properties of Novel Polyaromatic Profluorescent Isoindoline Nitroxide Probes
Publisher: Wiley
Date: 23-10-2008
Approaches to the Synthesis of a Water‐Soluble Carboxy Nitroxide
Publisher: Wiley
Date: 08-01-2013
Preserving Retinal Structure and Function with the Novel Nitroxide Antioxidant, DCTEIO
Publisher: Springer Science and Business Media LLC
Date: 14-07-2023
DOI: 10.1007/S11064-023-03978-W
Abstract: Oxidative stress is a major contributor to progressive neurodegenerative disease and may be a key target for the development of novel preventative and therapeutic strategies. Nitroxides have been successfully utilised to study changes in redox status (biological probes) and modulate radical-induced oxidative stress. This study investigates the efficacy of DCTEIO (5,6-dicarboxy-1,1,3,3-tetraethyllisoindolin-2-yloxyl), a stable, kinetically-persistent, nitroxide-based antioxidant, as a retinal neuroprotectant. The preservation of retinal function following an acute ischaemic/reperfusion (I/R) insult in the presence of DCTEIO was quantified by electroretinography (ERG). Inflammatory responses in retinal glia were analysed by GFAP and IBA-1 immunohistochemistry, and retinal integrity assessed by histology. A nitroxide probe combined with flow cytometry provided a rapid technique to assess oxidative stress and the mitigation offered by antioxidant compounds in cultured 661W photoreceptor cells. DCTEIO protected the retina from I/R-induced damage, maintaining retinal function. Histological analysis showed preservation of retinal integrity with reduced disruption and disorganisation of the inner and outer nuclear layers. I/R injury upregulated GFAP expression, indicative of retinal stress, which was significantly blunted by DCTEIO. The number of ‘activated’ microglia, particularly in the outer retina, in response to cellular stress was also significantly reduced by DCTEIO, potentially suggesting reduced inflammasome activation and cell death. DCTEIO mitigated oxidative stress in 661W retinal cell cultures, in a dose-dependent fashion. Together these findings demonstrate the potential of DCTEIO as a neuroprotective therapeutic for degenerative diseases of the CNS that involve an ROS-mediated component, including those of the retina e.g. age-related macular degeneration and glaucoma.
The application of a novel profluorescent nitroxide to monitor thermo-oxidative degradation of polypropylene
Publisher: Elsevier BV
Date: 09-2005
Synergic bactericidal effects of reduced graphene oxide and silver nanoparticles against Gram-positive and Gram-negative bacteria
Publisher: Springer Science and Business Media LLC
Date: 08-05-2017
DOI: 10.1038/S41598-017-01669-5
Abstract: Reduced graphene oxide (rGO) is a promising antibacterial material, the efficacy of which can be further enhanced by the addition of silver nanoparticles (nAg). In this study, the mechanisms of antibacterial activity of rGO–nAg nanocomposite against several important human pathogenic multi-drug resistant bacteria, namely Gram-positive coccal Staphylococcus aureus and Gram-negative rod-shaped Escherichia coli and Proteus mirabilis are investigated. At the same concentration (100 µg/ml), rGO–nAg nanocomposite was significantly more effective against all three pathogens than either rGO or nAg. The nanocomposite was equally active against P. mirabilis and S. aureus as systemic antibiotic nitrofurantoin, and significantly more effective against E. coli . Importantly, the inhibition was much faster in the case of rGO–nAg nanocomposite compared to nitrofurantoin, attributed to the synergistic effects of rGO–nAg mediated contact killing and oxidative stress. This study may provide new insights for the better understanding of antibacterial actions of rGO–nAg nanocomposite and for the better designing of graphene-based antibiotics or other biomedical applications.
Dramatic extension of tumor latency and correction of neurobehavioral phenotype in Atm-mutant mice with a nitroxide antioxidant
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.FREERADBIOMED.2006.06.018
Abstract: Mutations in the ATM gene (mutated in ataxia telangiectasia) in both humans and mice predispose to lymphoid tumors. A defect in this gene also causes neurodegeneration in humans and a less severe neurological phenotype in mice. There is some evidence that oxidative stress contributes to these defects, suggesting that antioxidants could alleviate the phenotype. We demonstrate here that the antioxidant 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO) dramatically delays the onset of thymic lymphomas in Atm(-/-) mice which is not due to an enhancement of apoptosis by CTMIO. We also show that this compound corrects neurobehavioral deficits in these mice and reduces oxidative damage to Purkinje cells. The likely mechanism of action of CTMIO is due to a reduction in oxidative stress, which is protective against both the tumor progression and the development of neurological abnormalities. These data suggest that antioxidant therapy has considerable potential in the management of ataxia telangiectasia and possibly other neurodegenerative disorders where oxidative stress is implicated.
Synthesis and properties of Mn(hfac)2 complexes of isoindoline nitroxide radicals
Publisher: Elsevier BV
Date: 07-2003
TMIO-PyrImid Hybrids are Profluorescent, Site-Directed Spin Labels for Nucleic Acids
Publisher: American Chemical Society (ACS)
Date: 28-10-2014
DOI: 10.1021/OL502003A
Abstract: We report the synthesis of a new class of molecules which are hybrids of long-lived tetramethylisoindolinoxyl (TMIO) radicals and the pyrido[1,2-a]benzimidazole (PyrImid) scaffold. These compounds represent a new lead for noncovalently binding nucleic acid probes, as they interact with nucleic acids with previously unreported C (DNA) and C/U (RNA) complementarity, which can be detected by electron paramagnetic resonance (EPR) techniques. They also have promising properties for fluorimetric analysis, as their fluorescent spin-quenched derivatives exhibit a significant Stokes shift.
5-[(E)-2-(4-Methoxycarbonylphenyl)ethenyl]-1,1,3,3-tetramethylisoindolin-2-yloxyl
Publisher: International Union of Crystallography (IUCr)
Date: 29-07-2006
The vibrational group frequency of the N-O stretching band of nitroxide stable free radicals
Publisher: Elsevier BV
Date: 09-2008
DOI: 10.1016/J.SAA.2007.08.017
Abstract: The group frequency of the N-O radical stretching vibration has received scant attention in the literature. The few existing treatments of the vibrational spectroscopy of nitroxides are incomplete at best and potentially misleading to workers in the field. To close this gap in the available knowledge, the existing literature on the vibrational spectra of nitroxide stable free radicals is critically reviewed with particular reference to the wavenumber position of the N-O* stretching vibration, nu(N-O*). Poor evidentiary bases for the assignment nu(N-O) were found in many instances. Ab initio Density Field Theory calculations using a model chemistry of UB3LYP at the 6-311++G(d,p) level were performed to obtain a theoretical band position of nu(N-O) for comparison with the published data. Large discrepancies between the theoretical and experimental values were found for the radical 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxyl, which currently sets the lower limit of the accepted wavenumber range of nu(N-O*), as well as for the nitronyl and iminyl nitroxides. The wavenumber position of nu(N-O*) was found to occur in the range 1450-1420cm(-1) for 5-membered cyclic nitroxides and 1395-1340cm(-1) for 6-membered cyclic and acyclic nitroxides. In nitronyl nitroxides, the symmetric stretching vibration occurs in the region 1470cm(-1), but coupling to other modes makes specific band assignments problematic for the nitronyl nitroxide group.
To Sonicate or Not to Sonicate PM Filters: Reactive Oxygen Species Generation Upon Ultrasonic Irradiation
Publisher: Informa UK Limited
Date: 20-11-2014
Real-time quantification of oxidative stress and the protective effect of nitroxide antioxidants
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.NEUINT.2015.11.003
Abstract: Nitroxides have been exploited as profluorescent probes for the detection of oxidative stress. In addition, they deliver potent antioxidant action and attenuate reactive oxygen species (ROS) in various models of oxidative stress, with these results ascribed to superoxide dismutase or redox and radical-scavenging actions. Our laboratory has developed a range of novel, biostable, isoindoline nitroxide-based antioxidants, DCTEIO and CTMIO. In this study we compared the efficiency of these novel compounds as antioxidant therapies in reducing ROS both in vivo (rat model) and in vitro (661W photoreceptor cells), with the established antioxidant resveratrol. By assessing changes in fluorescence intensity of a unique redox-responsive probe in the rat retina in vivo, we evaluated the ability of antioxidant therapy to (1) ameliorate ROS production and (2) reverse the accumulation of ROS after complete, acute ischemia followed by reperfusion (I/R). I/R injury induced a marked decrease in fluorescence intensity over 60 min of reperfusion, which was successfully ameliorated with each of the antioxidants. DCTEIO and CTMIO reversed the accumulation of ROS when administered intraocularly post ischemic insult, whereas, the effect of resveratrol was not significant. We also investigated our novel agents' capacity to prevent ROS-mediated metabolic dysfunction in the 661W photoreceptor cell line. Cellular stress induced by the oxidant, tert-butyl hydroperoxide, resulted in a loss of spare mitochondrial respiratory capacity (SMRC) and in the extracellular acidification rate in 661W cells. DCTEIO antioxidant administration successfully reduced the loss of SMRC. Together, these findings show we can quantify dynamic changes in cellular oxidative status in vivo and suggest that nitroxide-based antioxidants may provide greater protection against oxidative stress than the current state-of-the-art antioxidant treatments for ROS-mediated diseases.
Electron spin–lattice relaxation of nitroxyl radicals in temperature ranges that span glassy solutions to low-viscosity liquids
Publisher: Elsevier BV
Date: 03-2008
Correction: Naphthalene flanked diketopyrrolopyrrole based organic semiconductors for high performance organic field effect transistors
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NJ90083C
Abstract: Correction for ‘Naphthalene flanked diketopyrrolopyrrole based organic semiconductors for high performance organic field effect transistors’ by Qian Liu et al. , New J. Chem. , 2018, 42 , 12374–12385.
Driving selective aerobic oxidation of alkyl aromatics by sunlight on alcohol grafted metal hydroxides
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2SC20114C
Understanding the activity and selectivity of single atom catalysts for hydrogen and oxygen evolution via ab initial study
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7CY02463K
Abstract: To identify the specific activity sites for both the HER and OER in experimental realized single transition-metal atom decorated graphene sheets, we assume the number of metal–C bonds (coordination) determines the adsorption strength of reaction intermediates on the metal atom sites.
Dual acting antioxidant A1 adenosine receptor agonists
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.BMCL.2007.07.035
Abstract: Herein we report the synthesis and biological evaluation of some potent and selective A(1) adenosine receptor agonists, which incorporate a functionalised linker attached to an antioxidant moiety. N(6)-(2,2,5,5-Tetramethylpyrrolidin-1-yloxyl-3-ylmethyl)adenosine (VCP28, 2e) proved to be an agonist with high affinity (K(i)=50nM) and good selectivity (A(3)/A(1) > or = 400) for the A(1) adenosine receptor. N(6)-[4-[2-[1,1,3,3-Tetramethylisoindolin-2-yloxyl-5-amido]ethyl]phenyl]adenosine (VCP102, 5a) has higher binding affinity (K(i)=7 nM), but lower selectivity (A(3)/A(1)= approximately 3). All compounds bind weakly (K(i)>1 microM) to A(2A) and A(2B) receptors. The combination of A(1) agonist activity and antioxidant activity has the potential to produce cardioprotective effects.
Influence of oxygenated organic aerosols (OOAs) on the oxidative potential of diesel and biodiesel particulate matter
Publisher: American Chemical Society (ACS)
Date: 26-06-2013
DOI: 10.1021/ES4007433
Abstract: Generally, the magnitude of pollutant emissions from diesel engines running on biodiesel fuel is ultimately coupled to the structure of the fuel's constituent molecules. Previous studies demonstrated the relationship between the organic fraction of particulate matter (PM) and its oxidative potential. Herein, emissions from a diesel engine running on different biofuels were analyzed in more detail to explore the role that different organic fractions play in the measured oxidative potential. In this work, a more detailed chemical analysis of biofuel PM was undertaken using a compact time of flight aerosol mass spectrometer (c-ToF AMS). This enabled a better identification of the different organic fractions that contribute to the overall measured oxidative potentials. The concentration of reactive oxygen species (ROS) was measured using a profluorescent nitroxide molecular probe 9-(1,1,3,3-tetramethylisoindolin-2-yloxyl-5-ethynyl)-10-(phenylethynyl)anthracene (BPEAnit). Therefore, the oxidative potential of the PM, measured through the ROS content, although proportional to the total organic content in certain cases, shows a much higher correlation with the oxygenated organic fraction as measured by the c-ToF AMS. This highlights the importance of knowing the surface chemistry of particles for assessing their health impacts. It also sheds light onto new aspects of particulate emissions that should be taken into account when establishing relevant metrics for assessing health implications of replacing diesel with alternative fuels.
Preparation, properties, and mathematical modeling of microparticle drug delivery systems based on biodegradable amphiphilic triblock copolymers
Publisher: Wiley
Date: 08-04-2004
DOI: 10.1002/APP.20410
Application of profluorescent nitroxides for measurements of oxidative capacity of combustion generated particles
Publisher: National Library of Serbia
Date: 2012
Abstract: Oxidative stress caused by generation of free radicals and related reactive oxygen species (ROS) at the sites of deposition has been proposed as a mechanism for many of the adverse health outcomes associated with exposure to particulate matter (PM). Recently, a new profluorescent nitroxide molecular probe (BPEAnit) developed at QUT was applied in an entirely novel, rapid and non-cell based assay for assessing the oxidative potential of particles (i.e. potential of particles to induce oxidative stress). The technique was applied on particles produced by several combustion sources, namely cigarette smoke, diesel exhaust and wood smoke. One of the main findings from the initial studies undertaken at QUT was that the oxidative potential per PM mass significantly varies for different combustion sources as well as the type of fuel used and combustion conditions. However, possibly the most important finding from our studies was that there was a strong correlation between the organic fraction of particles and the oxidative potential measured by the PFN assay, which clearly highlights the importance of organic species in particle-induced toxicity.
Predicting a graphene-like WB4 nanosheet with a double Dirac cone, an ultra-high Fermi velocity and significant gap opening by spin–orbit coupling
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP00157F
Abstract: A stable WB 4 monolayer can deliver a sizable bandgap by spin–orbit coupling whilst maintaining high carrier mobility.
Free-radical gases on two-dimensional transition-metal disulfides (XS2, X = Mo/W): Robust half-metallicity for efficient nitrogen oxide sensors
Publisher: Beilstein Institut
Date: 05-06-2018
DOI: 10.3762/BJNANO.9.156
Abstract: The detection of single gas molecules is a highly challenging work because it requires sensors with an ultra-high level of sensitivity. By using density functional theory, here we demonstrate that the adsorption of a paramagnetic unpaired free radical gas (NO) on a monolayer of XS 2 (X = Mo, W) can trigger the transition from semiconductor to half metal. More precisely, the single-layer XS 2 (X = Mo, W) with NO adsorbed on it would behave like a metal in one spin channel while acting as a semiconductor in the other spin orientation. The half-metallicity is robust and independent of the NO concentration. In contrast, no half-metallic feature can be observed after the adsorption of other free radical gases such as NO 2 . The unique change in electronic properties after the adsorption of NO on transition-metal sulfides highlights an effective strategy to distinguish NO from other gas species by experimentally measuring spin-resolved transmission. Our results also suggest XS 2 (X = Mo, W) nanosheets can act as promising nanoscale NO sensors.
Catalytic Transformation of Aliphatic Alcohols to Corresponding Esters in O2under Neutral Conditions Using Visible-Light Irradiation
Publisher: American Chemical Society (ACS)
Date: 30-01-2015
DOI: 10.1021/JA511619C
Abstract: Selective oxidation of aliphatic alcohols under mild and base-free conditions is a challenging process for organic synthesis. Herein, we report a one-pot process for the direct oxidative esterification of aliphatic alcohols that is significantly enhanced by visible-light irradiation at ambient temperatures. The new methodology uses heterogenerous photocatalysts of gold-palladium alloy nanoparticles on a phosphate-modified hydrotalcite support and molecular oxygen as a benign oxidant. The alloy photocatalysts can absorb incident light, and the light-excited metal electrons on the surface of metal nanoparticles can activate the adsorbed reactant molecules. Tuning the light intensity and wavelength of the irradiation can remarkably change the reaction activity. Shorter wavelength light (<550 nm) drives the reaction more efficiently than light of longer wavelength (e.g., 620 nm), especially at low temperatures. The phosphate-exchanged hydrotalcite support provides sufficient basicity (and buffer) for the catalytic reactions thus, the addition of base is not required. The photocatalysts are efficient and readily recyclable. The findings reveal the first ex le of using "green" oxidants and light energy to drive direct oxidative esterification of aliphatic alcohols under base-free, mild conditions.
Dynamic, invivo, real-time detection of retinal oxidative status in a model of elevated intraocular pressure using a novel, reversibly responsive, profluorescent nitroxide probe.
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.EXER.2014.10.013
Abstract: Changes to the redox status of biological systems have been implicated in the pathogenesis of a wide variety of disorders including cancer, Ischemia-reperfusion (I/R) injury and neurodegeneration. In times of metabolic stress e.g. ischaemia/reperfusion, reactive oxygen species (ROS) production overwhelms the intrinsic antioxidant capacity of the cell, damaging vital cellular components. The ability to quantify ROS changes in vivo, is therefore essential to understanding their biological role. Here we evaluate the suitability of a novel reversible profluorescent probe containing a redox-sensitive nitroxide moiety (methyl ester tetraethylrhodamine nitroxide, ME-TRN), as an in vivo, real-time reporter of retinal oxidative status. The reversible nature of the probe's response offers the unique advantage of being able to monitor redox changes in both oxidizing and reducing directions in real time. After intravitreal administration of the ME-TRN probe, we induced ROS production in rat retina using an established model of complete, acute retinal ischaemia followed by reperfusion. After restoration of blood flow, retinas were imaged using a Micron III rodent fundus fluorescence imaging system, to quantify the redox-response of the probe. Fluorescent intensity declined during the first 60 min of reperfusion. The ROS-induced change in probe fluorescence was ameliorated with the retinal antioxidant, lutein. Fluorescence intensity in non-Ischemia eyes did not change significantly. This new probe and imaging technology provide a reversible and real-time response to oxidative changes and may allow the in vivo testing of antioxidant therapies of potential benefit to a range of diseases linked to oxidative stress.
New Spin on Organic Radical Batteries–An Isoindoline Nitroxide-Based High-Voltage Cathode Material
Publisher: American Chemical Society (ACS)
Date: 07-02-2018
Abstract: Organic electrode materials are a highly promising and environmentally benign class of battery materials with radical polymers being at the forefront of this research. Herein, we report the first ex le of the 1,1,3,3-tetramethylisoindolin-2-yloxyl class of nitroxides as an organic electrode material and the synthesis and application of a novel styrenic nitroxide polymer, poly(5-vinyl-1,1,3,3-tetramethylisoindolin-2-yloxyl) (PVTMIO). The polymer was synthesized from the precursor monomer, 2-methoxy-5-vinyl-1,1,3,3-tetramethylisoindoline, and subsequent oxidative deprotection yielded the electroactive radical species. Cyclic voltammetry revealed a high oxidation potential of 3.7 V versus Li, placing it among the top of the nitroxide class of electrode materials. The suitability of PVTMIO for utilization in a high-voltage organic radical battery was confirmed with a discharge capacity of 104.7 mAh g
Effect of atmospheric aging on volatility and reactive oxygen species of biodiesel exhaust nano-particles
Publisher: Copernicus GmbH
Date: 17-08-2015
Abstract: Abstract. In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric aging processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust.
The mechanism of initiation in the free radical polymerization of N-vinylcarbazole and N-vinylpyrrolidone
Publisher: Elsevier BV
Date: 1989
Direct Photocatalytic Conversion of Aldehydes to Esters Using Supported Gold Nanoparticles under Visible Light Irradiation at Room Temperature
Publisher: American Chemical Society (ACS)
Date: 08-08-2014
DOI: 10.1021/JP505552V
Wavelength-Specific Product Desorption as a Key to Raising Nitrile Yield of Primary Alcohol Ammoxidation over Illuminated Pd Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 31-01-2022
The effect of common agrichemicals on the environmental stability of polyethylene films
Publisher: Elsevier BV
Date: 10-2015
Development of a Redox‐Responsive Polymeric Profluorescent Probe
Publisher: Wiley
Date: 31-08-2016
Reactions of sulfoxides with reactive oxygen species to reveal the radical chemistry of pollution-derived particulate matter
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CC04024G
Abstract: The radical reactions of dimethylsulfoxide (DMSO) and tetrahydrothiophene-1-oxide (THTO) with reactive oxygen species (ROS) in the presence of a nitroxide radical scavenger have been evaluated both synthetically and in analytical practice.
Quantification of Particle-Bound Organic Radicals in Secondary Organic Aerosol
Publisher: American Chemical Society (ACS)
Date: 10-05-2019
Abstract: The chemical composition and evolution of secondary organic aerosol (SOA) in the atmosphere represents one of the largest uncertainties in our current understanding of air quality. Despite vast research, the toxicological mechanisms relating to adverse human health effects upon exposure to particulate matter are still poorly understood. Particle-bound reactive oxygen species (ROS) may substantially contribute to observed health effects by influencing aerosol oxidative potential (OP). The role of radicals in both the formation and aging of aerosol, as well as their contribution to aerosol OP, remains highly uncertain. The profluorescent spin trap BPEAnit (9,10-bis(phenylethynyl)anthracenenitroxide), previously utilized to study combustion-generated aerosol, has been applied to provide the first estimate of particle-bound radical concentrations in SOA. We demonstrate that SOA from different atmospherically important VOC precursors have different particle-bound radical concentrations, estimated for the ozonolysis of α-pinene (0.020 ± 0.0050 nmol/μg), limonene (0.0059 ± 0.0010 nmol/μg), and β-caryophyllene (0.0025 ± 0.00080 nmol/μg), highlighting the potential importance of OH-initiated formation of particle-bound organic radicals. Additionally, the lifetime of particle-bound radical species in α-pinene SOA was estimated, and a pseudo-first-order rate constant of k = 7.3 ± 1.7 × 10
Oxidative Potential of Logwood and Pellet Burning Particles Assessed by a Novel Profluorescent Nitroxide Probe
Publisher: American Chemical Society (ACS)
Date: 04-08-2010
DOI: 10.1021/ES100963Y
Abstract: This study reports the potential toxicological impact of particles produced during biomass combustion by an automatic pellet boiler and a traditional logwood stove under various combustion conditions using a novel profluorescent nitroxide probe, BPEAnit. This probe is weakly fluorescent but yields strong fluorescence emission upon radical trapping or redox activity. S les were collected by bubbling aerosol through an impinger containing BPEAnit solution, followed by fluorescence measurement. The fluorescence of BPEAnit was measured for particles produced during various combustion phases: at the beginning of burning (cold start), stable combustion after refilling with the fuel (warm start), and poor burning conditions. For particles produced by the logwood stove under cold-start conditions, significantly higher amounts of reactive species per unit of particulate mass were observed compared to emissions produced during a warm start. In addition, s ling of logwood burning emissions after passing through a thermodenuder at 250 degrees C resulted in an 80-100% reduction of the fluorescence signal of the BPEAnit probe, indicating that the majority of reactive species were semivolatile. Moreover, the amount of reactive species showed a strong correlation with the amount of particulate organic material. This indicates the importance of semivolatile organics in particle-related toxicity. Particle emissions from the pellet boiler, although of similar mass concentration, were not observed to lead to an increase in fluorescence signal during any of the combustion phases.
Profluorescent nitroxides: Sensors and stabilizers of radical-mediated oxidative damage
Publisher: Elsevier BV
Date: 09-2008
Chapter 3. Synthesis of Nitroxides and Alkoxyamines
Publisher: Royal Society of Chemistry
Date: 2015
EPR Characterization of the Quintet State for a Hydrocarbon Tetraradical with Two Localized 1,3-Cyclopentanediyl Biradicals Linked by meta-Phenylene as a Ferromagnetic Coupler
Publisher: American Chemical Society (ACS)
Date: 24-04-1996
DOI: 10.1021/JA953494M
Porphyrin containing isoindoline nitroxides as potential fluorescence sensors of free radicals
Publisher: World Scientific Pub Co Pte Lt
Date: 04-2011
DOI: 10.1142/S1088424611003203
Abstract: A series of new spin-labeled porphyrin containing isoindoline nitroxide moieties were synthesized and characterized as potential free radical fluorescence sensors. Fluorescence-suppression was observed in the free-base monoradical porphyrins, whilst the free-base biradical porphyrins exhibited highly suppressed fluorescence about three times greater than the monoradical porphyrins. The observed fluorescence-suppression was attributed to enhanced intersystem crossing resulting from electronexchange between the doublet nitroxide and the excited porphyrin fluorophore. Notably, fluorescencesuppression was not as strong in the related metalated porphyrins, possibly due to insufficient spin coupling between the nitroxide and the porphyrin. Continuous wave EPR spectroscopy of the diradical porphyrins in fluid solution suggests that the nitroxyl-nitroxyl interspin distance is long enough and tumbling is fast enough not to detect dipolar coupling.
Molecular Orientational Order of Nitroxide Radicals in Liquid Crystalline Media
Publisher: American Chemical Society (ACS)
Date: 12-05-2014
DOI: 10.1021/JP411729J
Abstract: The orientational distribution of a set of stable nitroxide radicals in aligned liquid crystals 5CB (nematic) and 8CB (smectic A) was studied in detail by numerical simulation of EPR spectra. The order parameters up to the 10th rank were measured. The directions of the principal orientation axes of the radicals were determined. It was shown that the ordering of the probe molecules is controlled by their interaction with the matrix molecules more than the inherent geometry of the probes themselves. The rigid fused phenanthrene-based (A5) and 2-azaphenalene (A4) nitroxides as well as the rigid core elongated C11 and 5α-cholestane (CLS) nitroxides were found to be most sensitive to the orientation of the liquid crystal matrixes.
Photo-induced proton coupled electron transfer from a benzophenone ‘antenna’ to an isoindoline nitroxide
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5RA20100D
Abstract: When exposed to light, a novel nitroxide-benzophenone hybrid will undergo an energy transfer process whereby the nitroxide enters an excited state which induces an efficient hydrogen atom transfer from unactivated alkanes.
Studies on alkyl esters of carboxybenzotriazole as inhibitors for copper corrosion
Publisher: Elsevier BV
Date: 06-2002
Synthesis of 1,1,3,3-tetraalkylisoindolines using a microwave-assisted grignard reaction
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/CH08008
Abstract: 1,1,3,3-Tetraalkylisoindolines are important intermediates in the preparation of stable nitroxides, such as 1,1,3,3-tetramethylisoindolin-2-oxyl, 1, and 1,1,3,3-tetraethylisoindolin-2-oxyl, 2. The limiting step in their preparation is the Grignard reaction between N-benzylphthalimide and the appropriate alkyl magnesium bromide, which typically proceeds in yields of ~28–40%. A microwave-assisted variation of this reaction has been optimized to give improved yields and reduced reaction times (45–60% and 2 h, respectively).
Novel sulfurated five-, seven- and nine-membered heterocycles: Unusual products derived from potential bisthionitroxide precursors
Publisher: Royal Society of Chemistry (RSC)
Date: 1995
DOI: 10.1039/C39950001449
The vibrational spectrum of the stable free radical 1,1,3,3-tetramethylisoindolin-2-yloxyl
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.SAA.2005.05.026
Abstract: Solid and solution IR and Raman spectra of a stable nitroxide radical, 1,1,3,3-tetramethylisoindolin-2-yloxyl (TMIO), are reported and compared to ab initio density functional theory calculations of the vibrational frequencies to obtain unequivocal band assignments, in particular of the NO stretching frequency, nu(NO). The band position was found to be at 1431 cm(-1) for the solid, which is well outside the previously published range of 1310-1380 cm(-1) for nitroxide radicals. This apparently anomalous peak position was confirmed by undertaking isotopic substitution studies through the preparation and recording of vibrational spectra of tetrakis(trideuteriomethyl)isoindolin-2-yloxyl ([2H12]-TMIO) and [2H12,15N]-TMIO analogues. Solution spectra of TMIO in methanol and CCl4 are assessed for possible solvent-dependent spin density distribution effects in the NO bond.
Inhibitive effect of 4- and 5- carboxybenzotriazole on copper corrosion in acidic sulphate and hydrogen sulphide solutions
Publisher: Elsevier BV
Date: 04-1999
Edaravone containing isoindoline nitroxides for the potential treatment of cardiovascular ischaemia
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1MD00041A
The synthesis and X-ray structural characterisation of an unusual seven-membered diaza-phospha-tetrathia heterocycle
Publisher: Royal Society of Chemistry (RSC)
Date: 1993
DOI: 10.1039/C39930001684
Novel polymer synthesis methodologies using combinations of thermally- and photochemically-induced nitroxide mediated polymerization
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4PY01270D
Abstract: The combination of thermally- and photochemically-induced polymerization using light sensitive alkoxyamines was investigated.
Profluorescent nitroxide sensors for monitoring the natural aging of polymer materials
Publisher: Elsevier BV
Date: 04-2020
The palladium-catalysed copper-free Sonogashira coupling of isoindoline nitroxides: a convenient route to robust profluorescent carbon–carbon frameworks
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B806963H
Abstract: A series of novel acetylene-substituted isoindoline nitroxides were synthesised via palladium-catalysed copper-free Sonogashira coupling. These results demonstrate that the Sonogashira reaction is suitable for the generation of a wide range of aryl nitroxides of expanded structural variety. The novel aryl-iodide containing nitroxide, 5-iodo-1,1,3,3-tetramethylisoindolin-2-yloxyl, 3, was a key intermediate for this coupling, giving acetylene-substituted isoindoline nitroxides in high yield. Subsequent reaction of the deprotected ethynyl nitroxide 12 with iodinated polyaromatics furnished novel aromatic nitroxides with extended-conjugation. Such nitroxides have been described as profluorescent, as their quantum yields are significantly lower than those of the corresponding diamagnetic derivatives. The quantum yields of the naphthyl- and phenanthryl-acetylene isoindoline nitroxides (13 and 14) were found to be 200-fold and 65-fold less than the non-radical methoxyamine derivatives (23 and 24). Ethyne- and butadiyne-linked nitroxide dimers could also be synthesised by this cross coupling methodology.
Profluorescent nitroxide sensors for monitoring photo-induced degradation in polymer films
Publisher: Elsevier BV
Date: 03-2017
Surface‐Plasmon‐Enhanced Transmetalation between Copper and Palladium Nanoparticle Catalyst
Publisher: Wiley
Date: 20-04-2022
Abstract: Surface‐plasmon‐mediated phenylacetylide intermediate transfer from the Cu to the Pd surface affords a novel mechanism for transmetalation, enabling wavelength‐tunable cross‐coupling and homo‐coupling reaction pathway control. C−C bond forming Sonogashira coupling and Glaser coupling reactions in O 2 atmosphere are efficiently driven by visible light over heterogeneous Cu and Pd nanoparticles as a mixed catalyst without base or other additives. The reaction pathway can be controlled by switching the excitation wavelength. Shorter wavelengths (400–500 nm) give the Glaser homo‐coupling diyne, whereas longer wavelength irradiation (500–940 nm) significantly increases the degree of cross‐coupling Sonogashira coupling products. The ratio of the activated intermediates of alkyne to the iodobenzene is wavelength dependent and this regulates transmetalation. This wavelength‐tunable reaction pathway is a novel way to optimize the product selectivity in important organic syntheses.
Diatomic sulfur detection by butadiene and norbornene: A cautionary note
Publisher: Elsevier BV
Date: 03-1997
Physicochemical Characterization of Particulate Emissions from a Compression Ignition Engine Employing Two Injection Technologies and Three Fuels
Publisher: American Chemical Society (ACS)
Date: 31-05-2011
DOI: 10.1021/ES200388F
Abstract: Alternative fuels and injection technologies are a necessary component of particulate emission reduction strategies for compression ignition engines. Consequently, this study undertakes a physicochemical characterization of diesel particulate matter (DPM) for engines equipped with alternative injection technologies (direct injection and common rail) and alternative fuels (ultra low sulfur diesel, a 20% biodiesel blend, and a synthetic diesel). Particle physical properties were addressed by measuring particle number size distributions, and particle chemical properties were addressed by measuring polycyclic aromatic hydrocarbons (PAHs) and reactive oxygen species (ROS). Particle volatility was determined by passing the polydisperse size distribution through a thermodenuder set to 300 °C. The results from this study, conducted over a four point test cycle, showed that both fuel type and injection technology have an impact on particle emissions, but injection technology was the more important factor. Significant particle number emission (54%-84%) reductions were achieved at half load operation (1% increase-43% decrease at full load) with the common rail injection system however, the particles had a significantly higher PAH fraction (by a factor of 2 to 4) and ROS concentrations (by a factor of 6 to 16) both expressed on a test-cycle averaged basis. The results of this study have significant implications for the health effects of DPM emissions from both direct injection and common rail engines utilizing various alternative fuels.
Profluorescent Nitroxides as Sensitive Probes of Oxidative Change and Free Radical Reactions
Publisher: CSIRO Publishing
Date: 2011
DOI: 10.1071/CH10442
Abstract: This paper presents a review on the use of tethered nitroxide–fluorophore molecules as probes of oxidative change and free radical generation and reaction. The proximity of the nitroxide free radical to the fluorophore suppresses the normal fluorescence emission process. Nitroxide free radical scavenging, metabolism or redox chemistry return the system to its natural fluorescent state and so these tethered nitroxide–fluorophore molecules are described as being profluorescent. A survey of profluorescent nitroxides found in the literature is provided as well as background on the mechanism of action and applications of these compounds as fluorometric probes within the fields of biological, materials and environmental sciences.
Investigation of polypropylene degradation during melt processing using a profluorescent nitroxide probe: A laboratory-scale study
Publisher: Elsevier BV
Date: 04-2011
First principles study of trirutile magnesium bismuth oxide: Ideal bandgap for photovoltaics, strain-mediated band-inversion and semiconductor-to-semimetal transition
Publisher: Elsevier BV
Date: 06-2018
Light-active azaphenalene alkoxyamines: fast and efficient mediators of a photo-induced persistent radical effect
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA18500B
Abstract: Reported is the first ex le of an alkoxyamine that quantitatively yields a nitroxide upon light exposure. The alkoxyamine is used to generate a light driven persistent radical effect and applied to radical insertion, exchange and polymerization reactions.
BODIPY‐Based Profluorescent Probes Containing Meso‐ and β‐Substituted Isoindoline Nitroxides
Publisher: Wiley
Date: 02-01-2017
The evaluation of new and isotopically labeled isoindoline nitroxides and an azaphenalene nitroxide for EPR oximetry
Publisher: Elsevier BV
Date: 08-2011
Inhibition of myeloperoxidase- and neutrophil-mediated oxidant production by tetraethyl and tetramethyl nitroxides
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.FREERADBIOMED.2014.02.011
Abstract: The powerful oxidant HOCl (hypochlorous acid and its corresponding anion, (-)OCl) generated by the myeloperoxidase (MPO)-H2O2-Cl(-) system of activated leukocytes is strongly associated with multiple human inflammatory diseases consequently there is considerable interest in inhibition of this enzyme. Nitroxides are established antioxidants of low toxicity that can attenuate oxidation in animal models, with this ascribed to superoxide dismutase or radical-scavenging activities. We have shown (M.D. Rees et al., Biochem. J. 421, 79-86, 2009) that nitroxides, including 4-amino-TEMPO (4-amino-2,2,6,6-tetramethylpiperidin-1-yloxyl radical), are potent inhibitors of HOCl formation by isolated MPO and activated neutrophils, with IC50 values of ~1 and ~6 µM respectively. The utility of tetramethyl-substituted nitroxides is, however, limited by their rapid reduction by biological reductants. The corresponding tetraethyl-substituted nitroxides have, however, been reported to be less susceptible to reduction. In this study we show that the tetraethyl species were reduced less rapidly than the tetramethyl species by both human plasma (89-99% decreased rate of reduction) and activated human neutrophils (62-75% decreased rate). The tetraethyl-substituted nitroxides retained their ability to inhibit HOCl production by MPO and activated neutrophils with IC50 values in the low-micromolar range in some cases inhibition was enhanced compared to tetramethyl substitution. Nitroxides with rigid structures (fused oxaspiro rings) were, however, inactive. Overall, these data indicate that tetraethyl-substituted nitroxides are potent inhibitors of oxidant formation by MPO, with longer plasma and cellular half-lives compared to the tetramethyl species, potentially allowing lower doses to be employed.
Relationship between Atmospheric PM-Bound Reactive Oxygen Species, Their Half-Lives, and Regulated Pollutants: Investigation and Preliminary Model
Publisher: American Chemical Society (ACS)
Date: 18-03-2020
The First Example of an Azaphenalene Profluorescent Nitroxide
Publisher: Wiley
Date: 14-09-2007
Computer simulation of the corrosion inhibition of copper in acidic solution by alkyl esters of 5-carboxybenzotriazole
Publisher: Elsevier BV
Date: 2003
Particle emissions, volatility, and toxicity from an ethanol fumigated compression ignition engine
Publisher: American Chemical Society (ACS)
Date: 08-12-2010
DOI: 10.1021/ES9021377
Abstract: Particle emissions, volatility, and the concentration of reactive oxygen species (ROS) were investigated for a pre-Euro I compression ignition engine to study the potential health impacts of employing ethanol fumigation technology. Engine testing was performed in two separate experimental c aigns with most testing performed at intermediate speed with four different load settings and various ethanol substitutions. A scanning mobility particle sizer (SMPS) was used to determine particle size distributions, a volatilization tandem differential mobility analyzer (V-TDMA) was used to explore particle volatility, and a new profluorescent nitroxide probe, BPEAnit, was used to investigate the potential toxicity of particles. The greatest particulate mass reduction was achieved with ethanol fumigation at full load, which contributed to the formation of a nucleation mode. Ethanol fumigation increased the volatility of particles by coating the particles with organic material or by making extra organic material available as an external mixture. In addition, the particle-related ROS concentrations increased with ethanol fumigation and were associated with the formation of a nucleation mode. The smaller particles, the increased volatility, and the increase in potential particle toxicity with ethanol fumigation may provide a substantial barrier for the uptake of fumigation technology using ethanol as a supplementary fuel.
Photocatalytic conversion of sugars to 5-hydroxymethylfurfural using aluminium(III) and fulvic acid
Publisher: Springer Science and Business Media LLC
Date: 08-2023
DOI: 10.1038/S41467-023-40090-7
Abstract: 5-hydroxymethylfurfural (HMF) is a valuable and essential platform chemical for establishing a sustainable, eco-friendly fine-chemical and pharmaceutical industry based on biomass. The cost-effective production of HMF from abundant C6 sugars requires mild reaction temperatures and efficient catalysts from naturally abundant materials. Herein, we report how fulvic acid forms complexes with Al 3+ ions that exhibit solar absorption and photocatalytic activity for glucose conversion to HMF in one-pot reaction, in good yield (~60%) and at moderate temperatures (80 °C). When using representative components of fulvic acid, catechol and pyrogallol as ligands, 70 and 67% HMF yields are achieved, respectively, at 70 °C. Al 3+ ions are not recognised as effective photocatalysts however, complexing them with fulvic acid components as light antennas can create new functionality. This mechanism offers prospects for new green photocatalytic systems to synthesise a range of substances that have not previously been considered.
Benzophenone-sensitized photolysis of the azoalkane diazabicyclo(2.2.1)hept-2-ene (DBH) : Trapping of the 1,3-cyclopentadiyl triplet diradical by a nitroxide.
Publisher: Elsevier BV
Date: 03-1991
Nitric Oxide and Nitroxides Can Act as Efficient Scavengers of Protein-Derived Free Radicals
Publisher: American Chemical Society (ACS)
Date: 04-10-2008
DOI: 10.1021/TX800183T
Abstract: Nitric oxide ((*)NO) may act as either a pro-oxidant or an antioxidant in biological systems. Although (*)NO and nitroxide radicals react slowly with most molecules, they react at near diffusion-controlled rates with other radicals and may therefore be efficient protective agents. This study assessed the ability of (*)NO and nitroxides to intercept specific protein-derived radicals and compared the efficacy of these species. Three protein radical systems were investigated as follows: BSA-derived radicals generated via radical transfer from H(2)O(2)-activated horseradish peroxidase, radicals formed on myoglobin via reaction with H(2)O(2), and carbon-centered radicals formed from amino acid hydroperoxides on exposure to Fe(2+)-EDTA. In each case, radicals were generated in the absence or presence of (*)NO or nitroxides of different size and charge. Concentration-dependent loss of the protein radicals was detected by electron paramagnetic resonance with both (*)NO and nitroxides and time-dependent consumption of (*)NO using an (*)NO electrode. The protein oxidation product dityrosine was significantly reduced by (*)NO and nitroxides, and 3,4-dihydroxyphenylalanine levels were reduced by nitroxides but not (*)NO. Overall, these studies demonstrate that (*)NO and nitroxides are efficient near-stoichiometric scavengers of protein radicals and, hence, are potential protective agents against protein oxidation reactions and resulting damage. These reactions show little dependence on nitroxide structure or charge.
Novel paramagnetic AT1 receptor antagonists
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CC14920B
Abstract: Novel paramagnetic selective angiotensin AT(1) receptor antagonists (sartans) bearing nitroxides (3, 4) have been prepared and their pharmacology evaluated in vitro as well as in vivo. Compounds 3, 4 proved to be effective sartans with pK(B) estimates in the range 6.2-9.1. In addition, the sodium salt (11) of 4 (R = Bu) is able to protect against vascular injury in hypertensive rats as determined by its ability to attenuate the development of intimal thickening caused by balloon injury of the carotid artery.
Synthesis of profluorescent isoindoline nitroxides via palladium-catalysed Heck alkenylation
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B504354A
Abstract: The synthesis of a new structural class of isoindoline nitroxides (aminoxyls), accessible via the palladium-catalysed Heck reaction, is presented. Reaction of the aryl bromoamine, 5-bromo-1,1,3,3-tetramethylisoindoline (4) or dibromoamine, 5,6-dibromo-1,1,3,3-tetramethylisoindoline (5) or the analogous bromonitroxides 6 and 7 with methyl acrylate gives the acrylate substituted tetramethylisoindoline amines 8 and 10 and nitroxides 12 and 14. Similarly, the reaction of the aryl bromides and dibromides 4-7 with methyl 4-vinylbenzoate gives the carboxystyryl substituted tetramethylisoindoline amines 9 and 11 and the analogous nitroxides 13 and 15. The carboxystyryl tetramethylisoindoline nitroxides demonstrate strongly suppressed fluorescence, which is revealed upon removal of the free radical by reduction or radical coupling.
Naphthalene flanked diketopyrrolopyrrole based organic semiconductors for high performance organic field effect transistors
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NJ01453A
Abstract: A newly reported alkylated naphthalene flanked DPP monomers without any further functionalization show high hole mobility in OFET devices.
The application of profluorescent nitroxides to detect reactive oxygen species derived from combustion-generated particulate matter: Cigarette smoke – A case study
Publisher: Elsevier BV
Date: 06-2010
Diketopyrrolopyrrole based organic semiconductors with different numbers of thiophene units: symmetry tuning effect on electronic devices
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7NJ03505E
Abstract: Three new DPP small molecules were synthesized and used them in OFET devices.
Physicochemical Characterization of Particulate Emissions from a Compression Ignition Engine: The Influence of Biodiesel Feedstock
Publisher: American Chemical Society (ACS)
Date: 15-11-2011
DOI: 10.1021/ES2018797
Abstract: This study undertook a physicochemical characterization of particle emissions from a single compression ignition engine operated at one test mode with 3 biodiesel fuels made from 3 different feedstocks (i.e., soy, tallow, and canola) at 4 different blend percentages (20%, 40%, 60%, and 80%) to gain insights into their particle-related health effects. Particle physical properties were inferred by measuring particle number size distributions both with and without heating within a thermodenuder (TD) and also by measuring particulate matter (PM) emission factors with an aerodynamic diameter less than 10 μm (PM(10)). The chemical properties of particulates were investigated by measuring particle and vapor phase Polycyclic Aromatic Hydrocarbons (PAHs) and also Reactive Oxygen Species (ROS) concentrations. The particle number size distributions showed strong dependency on feedstock and blend percentage with some fuel types showing increased particle number emissions, while others showed particle number reductions. In addition, the median particle diameter decreased as the blend percentage was increased. Particle and vapor phase PAHs were generally reduced with biodiesel, with the results being relatively independent of the blend percentage. The ROS concentrations increased monotonically with biodiesel blend percentage but did not exhibit strong feedstock variability. Furthermore, the ROS concentrations correlated quite well with the organic volume percentage of particles - a quantity which increased with increasing blend percentage. At higher blend percentages, the particle surface area was significantly reduced, but the particles were internally mixed with a greater organic volume percentage (containing ROS) which has implications for using surface area as a regulatory metric for diesel particulate matter (DPM) emissions.
Experimental evidence for long-range stabilizing and destabilizing interactions between charge and radical sites in distonic ions
Publisher: Elsevier BV
Date: 2019
Two-dimensional GeP3 as a high capacity electrode material for Li-ion batteries
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CP04758D
Abstract: Monolayer GeP 3 is predicted to be an ideal anode material for lithium battery with ultrahigh-capacity, low diffuse barrier and low average open-circuit voltage.
The cheletropic trapping of nitric oxide by the bis-ketene 1,2-dicarbonylcyclohexa-3,5-diene and the diene 3,4-diphenyl-2,5-dimethyl-2,4-hexadiene.
Publisher: Elsevier BV
Date: 03-1996
In search of a new class of stable nitroxide: synthesis and reactivity of a peri-substituted N,N-bissulfonylhydroxylamine
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0OB00976H
Abstract: Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time.
Surface‐Plasmon‐Enhanced Transmetalation between Copper and Palladium Nanoparticle Catalyst
Publisher: Wiley
Date: 20-04-2022
Abstract: Surface‐plasmon‐mediated phenylacetylide intermediate transfer from the Cu to the Pd surface affords a novel mechanism for transmetalation, enabling wavelength‐tunable cross‐coupling and homo‐coupling reaction pathway control. C−C bond forming Sonogashira coupling and Glaser coupling reactions in O 2 atmosphere are efficiently driven by visible light over heterogeneous Cu and Pd nanoparticles as a mixed catalyst without base or other additives. The reaction pathway can be controlled by switching the excitation wavelength. Shorter wavelengths (400–500 nm) give the Glaser homo‐coupling diyne, whereas longer wavelength irradiation (500–940 nm) significantly increases the degree of cross‐coupling Sonogashira coupling products. The ratio of the activated intermediates of alkyne to the iodobenzene is wavelength dependent and this regulates transmetalation. This wavelength‐tunable reaction pathway is a novel way to optimize the product selectivity in important organic syntheses.
Predicting Two-Dimensional C3B/C3N van der Waals p-n Heterojunction with Strong Interlayer Electron Coupling and Enhanced Photocurrent
Publisher: American Chemical Society (ACS)
Date: 07-02-2018
DOI: 10.1021/ACS.JPCLETT.7B03449
Abstract: The interlayer coupling in 2D van der Waals (vdW) heterostructures (HTS) plays the main role in generating new physics. However, the interlayer coupling is often weak, and little information on the strength of interlayer interaction in HTS is available. On the basis of density functional theory, we demonstrate that an effective electron coupling can be created in 2D C
On the efficiency of impingers with fritted nozzle tip for collection of ultrafine particles
Publisher: Elsevier BV
Date: 02-2009
Lifetime prediction of biodegradable polymers
Publisher: Elsevier BV
Date: 08-2017
Experimental and Theoretical Studies of the Redox Potentials of Cyclic Nitroxides
Publisher: American Chemical Society (ACS)
Date: 07-08-2008
DOI: 10.1021/JO801099W
Abstract: The redox potentials of 25 cyclic nitroxides from four different structural classes (pyrrolidine, piperidine, isoindoline, and azaphenalene) were determined experimentally by cyclic voltammetry in acetonitrile, and also via high-level ab initio molecular orbital calculations. It is shown that the potentials are influenced by the type of ring system, ring substituents and/or groups surrounding the radical moiety. For the pyrrolidine, piperidine, and isoindolines there is excellent agreement (mean absolute deviation of 0.05 V) between the calculated and experimental oxidation potentials for the azaphenalenes, however, there is an extraordinary discrepancy (mean absolute deviation of 0.60 V), implying that their one-electron oxidation might involve additional processes not considered in the theoretical calculations. This recently developed azaphenalene class of nitroxide represents a new variant of a nitroxide ring fused to an aromatic system and details of the synthesis of five derivatives involving differing aryl substitution are also presented.
The Synthesis of Novel Isoindoline Nitroxides Bearing Water‐Solubilising Functionality
Publisher: Wiley
Date: 30-03-2009
Abstract: A range of novel tetramethyl‐ and tetraethylisoindolinenitroxides, possessing aryl‐linked carboxylic acids, amines, alcohols and phosphonic acids were prepared. Notably, the chemistry established for the aromatic dibromination of the tetramethylisoindolines was not easily transferred to the corresponding tetraethylisoindoline system. Instead, various tetraethylisoindoline analogues were accessed by the oxidation of methyl groups attached to the aromatic ring to give the carboxylic acids. The increased steric bulk of the tetraethyl structures should limit bio‐reduction and these compounds may have potential as antioxidants.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Design, synthesis and biological evaluation of hybrid nitroxide-based non-steroidal anti-inflammatory drugs
Publisher: Elsevier BV
Date: 03-2018
Photolysis of dioxiranes in the presence of a nitroxide radical scavenger: The intermediacy of radical anion and diyl species in the production and trapping of methyl and trifluoromethyl radicals
Publisher: Royal Society of Chemistry (RSC)
Date: 1991
DOI: 10.1039/C39910000771
Profluorescent nitroxides: Thermo-oxidation sensors for stabilised polypropylene
Publisher: Elsevier BV
Date: 10-2010
Review-evaluating the molecular assays for measuring the oxidative potential of particulate matter
Publisher: National Library of Serbia
Date: 2015
Abstract: Several cell-free assays are currently used to quantify and detect the Reactive Oxygen Species (ROS). All of them have certain limitations, do not provide direct comparison of results and, to date, none of these assays have been acknowledged as the most suitable acellular assay and none has yet been adopted for investigation of potential PM toxicity. These assays include DTT, ascorbic acid, DCFHDA and PFN assays which have been used in measurements of the particles generated from various combustion sources such as diesel engine, wood smoke (or biomass burning) and cigarette smoke, as well as for outdoor measurements. All the probes use different units for expressing redox properties of PM. Also, their reactivity is being triggered by different types of ROS. This limits the direct comparison of the results that are reporting the toxicity of the same aerosol type measured with various probes. This study is evaluating and comparing the various assays in order to develop deeper understanding of their capabilities, selectivity as well as improve understanding of the underlying chemical mechanisms.
Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid Using O2 and a Photocatalyst of Co-thioporphyrazine Bonded to g-C3N4
Publisher: American Chemical Society (ACS)
Date: 09-10-2017
DOI: 10.1021/JACS.7B08861
Abstract: Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is one of the key reactions for producing chemical commodities from biomass and their derivatives. The challenge for this reaction is to develop an efficient catalytic process that can be conducted under mild conditions (room temperature and atmospheric pressure, using oxygen molecules in air as the oxidant) and a recyclable catalyst. Herein we report a photocatalyst of cobalt thioporphyrazine (CoPz) dispersed on g-C
Generation of Profluorescent Isoindoline Nitroxides Using Click Chemistry
Publisher: American Chemical Society (ACS)
Date: 17-05-2011
DOI: 10.1021/JO200613R
Abstract: Novel profluorescent nitroxides bearing a triazole linker between the coumarin fluorophore and an isoindoline nitroxide were prepared in good yields using the copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction (CuAAC). Nitroxides containing 7-hydroxy and 7-diethylamino substitution on their coumarin rings displayed significant fluorescence suppression, and upon reaction with methyl radicals, normal fluorescence emission was returned. The fluorescence emission for the 7-hydroxycoumarin nitroxide and its diamagnetic analogue was found to be strongly influenced by pH with maximal fluorescence emission achieved in basic solution. Solvent polarity was also shown to affect fluorescence emission. The significant difference in fluorescence output between the nitroxides and their corresponding diamagnetic analogues makes these compounds ideal tools for monitoring processes involving free-radical species.
Crystal structure of 2,4,4-triphenyl-2-aza-3-oxa-bicyclo[3.3.0]oct-5-ene, C24H21NO
Publisher: Walter de Gruyter GmbH
Date: 02-1991
Evaluation of dendritic gadolinium complexes as MRI contrast agents
Publisher: SAGE Publications
Date: 11-2004
Abstract: A series of dendritic gadolinium complexes based on dendrimers with 1,4,7,10-tetraazacyclododecane as the core were synthesized. Both diethylenetriaminepentaacetic acid and pyridoxamine were incorporated to the amine groups on the surface to give the dendritic ligands. These dendritic ligands were then reacted with gadolinium chloride to yield the corresponding dendritic gadolinium complexes. The dendritic ligands and their gadolinium complexes were characterized by 1HNMR, IR, UV and elemental analysis. Relaxivity studies showed that the dendritic gadolinium complexes have higher relaxation effectiveness than that of the clinically used small molecular gadolinium complexes. Magnetic resonance imaging of the liver in rats indicated that the dendritic gadolinium complex containing pyridoxamine enhances the image contrast of the liver, provides prolonged intravascular duration and produces highly contrasted visualization of blood vessels in the liver.
Sensitive luminescence techniques to study the early stages of polymer oxidation
Publisher: Elsevier BV
Date: 12-2013
Synthesis and properties of fullerene C60 and C70 spin probes containing isoindoline nitroxides
Publisher: Informa UK Limited
Date: 03-01-2015
Computational Design of Cyclic Nitroxides as Efficient Redox Mediators for Dye‐Sensitized Solar Cells
Publisher: Wiley
Date: 25-04-2012
Abstract: Cyclic nitroxide radicals represent promising alternatives to the iodine‐based redox mediator commonly used in dye‐sensitized solar cells (DSSCs). To date DSSCs with nitroxide‐based redox mediators have achieved energy conversion efficiencies of just over 5 % but efficiencies of over 15 % might be achievable, given an appropriate mediator. The efficacy of the mediator depends upon two main factors: it must reversibly undergo one‐electron oxidation and it must possess an oxidation potential in a range of 0.600–0.850 V (vs. a standard hydrogen electrode (SHE) in acetonitrile at 25 °C). Herein, we have examined the effect that structural modifications have on the value of the oxidation potential of cyclic nitroxides as well as the reversibility of the oxidation process. These included alterations to the N ‐containing skeleton (pyrrolidine, piperidine, isoindoline, azaphenalene, etc.), as well as the introduction of different substituents (alkyl‐, methoxy‐, amino‐, carboxy‐, etc.) to the ring. Standard oxidation potentials were calculated using high‐level ab initio methodology that was demonstrated to be very accurate (with a mean absolute deviation from experimental values of only 16 mV). An optimal value of 1.45 for the electrostatic scaling factor for UAKS radii in acetonitrile solution was obtained. Established trends in the values of oxidation potentials were used to guide molecular design of stable nitroxides with desired , and a number of compounds were suggested for potential use as enhanced redox mediators in DSSCs.
A Novel Profluorescent Dinitroxide for Imaging Polypropylene Degradation
Publisher: American Chemical Society (ACS)
Date: 15-02-2008
DOI: 10.1021/MA701944P
Improving the Yield of the Exhaustive Grignard Alkylation of N-Benzylphthalimide
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/CH12528
Abstract: The tetraalkylation of N-benzylphthalimide is the major yield limiting step in the common synthetic route to isoindoline nitroxides. The progress of this reaction was found to be limited by the formation of previously unobserved mono- and dialkyl side products that do not lead to the desired product. The yield for the tetraalkylation of N-benzylphthalimide with ethylmagnesium iodide could be increased (60 % over two steps) when a stepwise addition sequence was employed. The new two-step synthesis offers a practical preparative scale alternative to the current approach.
Influence of oxygen content of the certain types of biodiesels on particulate oxidative potential
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.SCITOTENV.2015.12.036
Abstract: Oxidative potential (OP) is related to the organic phase, specifically to its oxygenated organic fraction (OOA). Furthermore, the oxygen content of fuel molecules has significant influence on particulate OP. Thus, this study aimed to explore the actual dependency of the OOA and ROS to the oxygen content of the fuel. In order to reach the goal, different biodiesels blends, with various ranges of oxygen content have been employed. The compact time of flight aerosol mass spectrometer (c-ToF AMS) enabled better identification of OOA. ROS monitored by using two assays: DTT and BPEA-nit. Despite emitting lower mass, both assays agreed that oxygen content of a biodiesel is directly correlated with its OOA, and highly related to its OP. Hence, the more oxygen included in the considered biodiesels, the higher the OP of PM emissions. This highlights the importance of taking oxygen content into account while assessing emissions from new fuel types, which is relevant from a health effects standpoint.
Application of the new EPR spin trap 1,1,3-trimethylisoindole N-oxide (TMINO) in trapping HO. and related biologically important radicals
Publisher: Royal Society of Chemistry (RSC)
Date: 2003
DOI: 10.1039/B300644A
Abstract: The new EPR spin trap, 1,1,3-trimethylisoindole N-oxide (TMINO), very efficiently scavenges several Fenton-derived carbon- and oxygen-centred radicals including hydroxyl, formyl and alkyl radicals. The adducts display good stability and narrow EPR line-widths, allowing the detection of the expected radicals as well as two-dimensional (time-resolved) EPR experiments. Trapping experiments were also undertaken with superoxide radicals (giving no EPR signals) and nitric oxide (which gave strong EPR signals attributed to the action of higher oxides of nitrogen). The selectivity of TMINO towards HO. with respect to superoxide radicals demonstrates its potential as a useful spin-trap.
Highly efficient, stoichiometric radical exchange reactions using isoindoline profluorescent nitroxides
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0PY00015A
Prognostic Tools for Lifetime Prediction of Aircraft Coatings: Paint Degradation
Publisher: Trans Tech Publications, Ltd.
Date: 10-2010
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMR.138.137
Abstract: A direct interrogation, portable analysis technique (portable FT-IR) and a novel environment-monitoring profluorescent sensor for studying aircraft coating degradation have been developed. For the direct interrogation approach, a standard military aircraft paint: 459-line Anzothane flexible polyurethane (lead free) has been used to illustrate a new potential field technique to evaluate coating service lifetime, portable FT-IR. This technique allows direct analysis of chemical changes within the degrading coatings and has the potential to evaluate service lifetime when coupled with advanced statistical analysis methods (chemometrics). The degradation environment monitoring sensors are embodied in a profluorescent environment-sensitive witness patch that may be analysed in-service by a field-deployable fluorescence spectrometer. Accelerated ageing for both the paint and the witness patches has been undertaken and their capabilities as aircraft paint degradation monitors assessed.
Biological Relevance of Free Radicals and Nitroxides
Publisher: Springer Science and Business Media LLC
Date: 06-10-2017
DOI: 10.1007/S12013-016-0759-0
Abstract: Nitroxides are stable, kinetically-persistent free radicals which have been successfully used in the study and intervention of oxidative stress, a critical issue pertaining to cellular health which results from an imbalance in the levels of damaging free radicals and redox-active species in the cellular environment. This review gives an overview of some of the biological processes that produce radicals and other reactive oxygen species with relevance to oxidative stress, and then discusses interactions of nitroxides with these species in terms of the use of nitroxides as redox-sensitive probes and redox-active therapeutic agents.
Diketopyrrolopyrrole-Based Dual-Acceptor Copolymers to Realize Tunable Charge Carrier Polarity of Organic Field-Effect Transistors and High-Performance Nonvolatile Ambipolar Flash Memories
Publisher: American Chemical Society (ACS)
Date: 28-04-2020
Cycloaddition of nitrosobenzene to a trimethylenemethane diradical: The first case of isoxazoline formation from in situ generated nitroxides through spin trapping.
Publisher: Elsevier BV
Date: 1991
Modular design of profluorescent polymer sensors
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5PY00120J
Abstract: Through orthogonal coupling chemistries, the synthesis of profluorescent nitroxide containing polymers for applications as radical or redox sensors is achieved.
Reducing the Hydrogen Atom Abstraction Efficiencies of Benzophenone-Based Photosensitive Alkoxyamines
Publisher: American Chemical Society
Date: 2018
Inhibition of copper corrosion by coatings of alkyl esters of carboxybenzotriazole
Publisher: Elsevier BV
Date: 11-2002
Synthesis and properties of novel porphyrin spin probes containing isoindoline nitroxides
Publisher: Elsevier BV
Date: 07-2007
DOI: 10.1016/J.FREERADBIOMED.2007.03.032
Abstract: We report the synthesis of novel spin-labeled porphyrins containing isoindoline nitroxides (TMIO-APTPP and TMIO-APTSPP) and their manganese complexes (Mn-TMIO-APTPP and Mn-TMIO-APTSPP). These compounds represent potential new tools for electron paramagnetic resonance (EPR) as well as novel spin probes. Both TMIO-APTPP and TMIO-APTSPP have characteristic UV absorption peaks of free base porphyrin, while the characteristic absorption peaks of their manganese complexes Mn-TMIO-APTPP and Mn-TMIO-APTSPP shifted to shorter wavelengths. Electron paramagnetic resonance (EPR) spectroscopy indicated that these compounds all exhibit hyperfine splittings characteristic of EPR spectra of tetramethylisoindoline nitroxides, the typical nitroxide g values of approximately 2.006, and nitrogen isotropic hyperfine coupling constants (a(N) values) of about 14 G (293 K). The observed linewidths (La) for TMIO-APTSPP (0.73 G) and Mn-TMIO-APTSPP (0.65 G) in distilled water are significantly narrower than for TMIO-APTPP (1.475 G) and Mn-TMIO-APTPP (1.55 G) in chloroform.
One-Electron Oxidation and Reduction Potentials of Nitroxide Antioxidants: A Theoretical Study
Publisher: American Chemical Society (ACS)
Date: 12-2007
DOI: 10.1021/JP074250E
Abstract: High-level ab initio calculations have been used to determine the oxidation and reduction potentials of a large number of nitroxides including derivatives of piperidine, pyrrolidine, isoindoline, and azaphenalene, substituted with COOH, NH2, NH3+, OCH3, OH, and NO2 groups, with a view to (a) identifying a low-cost theoretical procedures for the determination of electrode potentials of nitroxides and (b) studying the effect of substituents on these systems. Accurate oxidation and reduction potentials to within 40 mV (3.9 kJ mol(-1)) of experimental values were found using G3(MP2)-RAD//B3-LYP/6-31G(d) gas-phase energies and PCM solvation calculations at the B3-LYP/6-31G(d) level. For larger systems, an ONIOM method in which G3(MP2)-RAD calculations for the core are combined with lower-cost RMP2/6-311+G(3df,2p) calculations for the full system, was able to approximate G3(MP2)-RAD values (to within 1.6 kJ mol(-1)) at a fraction of the computational cost. The overall ring structure has more effect on the electrode potentials than the inclusion of substituents. Azaphenalene derivatives display the lowest oxidation potentials and least negative reduction potentials and are thus the most promising target to function as antioxidants in biological systems. Piperidine and pyrrolidine derivatives have intermediate oxidation potentials but on average pyrrolidine derivatives display more negative reduction potentials. Isoindoline derivatives show higher oxidation potentials and more negative reduction potentials. Within a ring, the substituents have a relatively small effect with electron donating groups such as amino and hydroxy groups stabilizing the oxidized species and electron withdrawing groups such as carboxy groups stabilizing the reduced species, as expected.
The excited multiplet states of 5,10,15-tri-n-pentyl-20 (1′,1′,3′, 3′-tetramethylisoindolin -2′-yloxyl-5′-yl)porphyrinato zinc(II)
Publisher: Elsevier BV
Date: 03-2003
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