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Full-Text Articles in Social and Behavioral Sciences
Carbanions: Formation, Structure And Thermochemistry, Stephen J. Blanksby, John H. Bowie
Carbanions: Formation, Structure And Thermochemistry, Stephen J. Blanksby, John H. Bowie
Stephen Blanksby
This chapter deals with even-electron carbanions: their formation, structure and thermochemical properties in the gas phase. There are a number of excellent reviews already available on the chemistry of carbanions: these discuss in the main, reactivity and anion molecule chemistry.1-4 In this chapter we focus primarily on the formation, structure and thermochemistry of simple hydrocarbon anions while other chapters in this encyclopaedia cover the broader aspects of carbanion chemistry (see Volume 1, “Strained Ring and Highly Basic Carbanions” and this volume, Reactions of Organic Molecules with Organic Ions: “Reactions of Anions with Carbonyl Centres: C–C Bond Forming Reactions”, and Unimolecular …
Base-Induced Decomposition Of Alkyl Hydroperoxides In The Gas Phase. Part 3. Kinetics And Dynamics In Ho + Ch3ooh, C2h5ooh, And Tert-C4h9ooh Reactions, Shuji Kato, G Barney Ellison, Veronica Bierbaum, Stephen J. Blanksby
Base-Induced Decomposition Of Alkyl Hydroperoxides In The Gas Phase. Part 3. Kinetics And Dynamics In Ho + Ch3ooh, C2h5ooh, And Tert-C4h9ooh Reactions, Shuji Kato, G Barney Ellison, Veronica Bierbaum, Stephen J. Blanksby
Stephen Blanksby
The ECO2 elimination reactions of alkyl hydroperoxides proceed via abstraction of an α-hydrogen by a base: X− + R1R2HCOOH → HX + R1R2CO + HO−. Efficiencies and product distributions for the reactions of the hydroxide anion with methyl, ethyl, and tert-butyl hydroperoxides are studied in the gas phase. On the basis of experiments using three isotopic analogues, HO− + CH3OOH, HO− + CD3OOH, and H18O− + CH3OOH, the overall intrinsic reaction efficiency is determined to be 80% or greater. The ECO2 decomposition is facile for these methylperoxide reactions, and predominates over competing proton transfer at the hydroperoxide moiety. The CH3CH2OOH …
Identification Of Phospholipids In Human Meibum By Nano-Electrospray Ionisation Tandem Mass Spectrometry, Jennifer T. Saville, Zhenjun Zhao, Mark Dp Willcox, Manjula A. Ariyavidana, Stephen J. Blanksby, Todd W. Mitchell
Identification Of Phospholipids In Human Meibum By Nano-Electrospray Ionisation Tandem Mass Spectrometry, Jennifer T. Saville, Zhenjun Zhao, Mark Dp Willcox, Manjula A. Ariyavidana, Stephen J. Blanksby, Todd W. Mitchell
Stephen Blanksby
Meibum is believed to be the major source of tear !lm lipids, which are vital in the prevention of excessevaporation of the aqueous phase. The complete lipid composition of meibum has yet to be established.While earlier studies reported the presence of phospholipids in human meibum, recent mass spectrometricstudies have not detected them. In this study we use electrospray ionisation tandem massspectrometry to investigate the presence of phospholipids in meibum and provide comparison to thephospholipid pro!le of tears.Lipids were extracted from human meibum and tear samples using standard biphasic methods andanalysed by nano-electrospray ionisation tandem mass spectrometry using targeted ion scans. …
The Loss Of Carbon Dioxide From Activated Perbenzoate Anions In The Gas Phase: Unimolecular Rearrangement Via Epoxidation Of The Benzene Ring, David G. Harman, Aravind Ramachandran, Michelle Gracanin, Stephen J. Blanksby
The Loss Of Carbon Dioxide From Activated Perbenzoate Anions In The Gas Phase: Unimolecular Rearrangement Via Epoxidation Of The Benzene Ring, David G. Harman, Aravind Ramachandran, Michelle Gracanin, Stephen J. Blanksby
Stephen Blanksby
The unimolecular reactivities of a range of perbenzoate anions (X−C6H5CO3-), including the perbenzoate anion itself (X = H), nitroperbenzoates (X = para-, meta-, ortho-NO2), and methoxyperbenzoates (X = para-, meta-OCH3) were investigated in the gas phase by electrospray ionization tandem mass spectrometry. The collision-induced dissociation mass spectra of these compounds reveal product ions consistent with a major loss of carbon dioxide requiring unimolecular rearrangement of the perbenzoate anion prior to fragmentation. Isotopic labeling of the perbenzoate anion supports rearrangement via an initial nucleophilic aromatic substitution at the ortho carbon of the benzene ring, while data from substituted perbenzoates indicate that …
Ozone Induced Dissociation: Elucidation Of Double Bond Position Within Mass-Selected Lipid Ions, Michael C. Thomas, Todd W. Mitchell, David G. Harman, Jane M. Deeley, Jessica R. Nealon, Stephen J. Blanksby
Ozone Induced Dissociation: Elucidation Of Double Bond Position Within Mass-Selected Lipid Ions, Michael C. Thomas, Todd W. Mitchell, David G. Harman, Jane M. Deeley, Jessica R. Nealon, Stephen J. Blanksby
Stephen Blanksby
Ions formed from lipids during electrospray ionization of crude lipid extracts have been mass-selected within a quadrupole linear ion trap mass spectrometer and allowed to react with ozone vapor. Gas-phase ion−molecule reactions between unsaturated lipid ions and ozone are found to yield two primary product ions for each carbon−carbon double bond within the molecule. The mass-to-charge ratios of these chemically induced fragments are diagnostic of the position of unsaturation within the precursor ion. This novel analytical technique, dubbed ozone-induced dissociation (OzID), can be applied both in series and in parallel with conventional collision-induced dissociation (CID) to provide near-complete structural assignment …
Differences In Membrane Acyl Phospholipid Composition Between An Endothermic Mammal And An Ectothermic Reptile Are Not Limited To Any Phospholipid Class, Stephen J. Blanksby, Todd W. Mitchell, Anthony J. Hulbert, Paul Else, K Ekroos
Differences In Membrane Acyl Phospholipid Composition Between An Endothermic Mammal And An Ectothermic Reptile Are Not Limited To Any Phospholipid Class, Stephen J. Blanksby, Todd W. Mitchell, Anthony J. Hulbert, Paul Else, K Ekroos
Stephen Blanksby
This study examined questions concerning differences in the acyl composition of membrane phospholipids that have been linked to the faster rates of metabolic processes in endotherms versus ectotherms. In liver, kidney, heart and brain of the ectothermic reptile, Trachydosaurus rugosus, and the endothermic mammal, Rattus norvegicus, previous findings of fewer unsaturates but a greater unsaturation index (UI) in membranes of the mammal versus those of the reptile were confirmed. Moreover, the study showed that the distribution of phospholipid head-group classes was similar in the same tissues of the reptile and mammal and that the differences in acyl composition were present …
Oxidation Of 4-Substituted Tempo Derivatives Reveals Modifications At The 1- And 4-Positions, David Marshall, M L. Christian, G Gryn'ova, M L. Coote, Philip J. Barker, Stephen J. Blanksby
Oxidation Of 4-Substituted Tempo Derivatives Reveals Modifications At The 1- And 4-Positions, David Marshall, M L. Christian, G Gryn'ova, M L. Coote, Philip J. Barker, Stephen J. Blanksby
Stephen Blanksby
Potenital pathways for the deactivation of hindered amine light stabilisers (HALS) have been investigated by observing reactions of model compounds - based on 4-substituted derivatives of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) - with hydroxyl radicals. In these reactions, dilute aqueous suspensions of photocatalytic nanoparticulate titanium dioxide were irradiated with UV light in the presence of water-soluble TEMPO derivatives. Electron spin resonance (ESR) and electrospray ionisation mass-spectrometry (ESI-MS) data were acquired to provide complementary structural elucidation of the odd- and even-electron products of these reactions and both techniques show evidence for the formation of 4-oxo-TEMPO (TEMPONE). TEMPONE formation from the 4-substituted TEMPO compounds is …
Direct Detection Of Additives And Degradation Products From Polymers By Liquid Extraction Surface Analysis Employing Chip-Based Nanospray Mass Spectrometry, Martin Paine, Phillip Barker, Shane A. Maclaughlin, Todd W. Mitchell, Stephen J. Blanksby
Direct Detection Of Additives And Degradation Products From Polymers By Liquid Extraction Surface Analysis Employing Chip-Based Nanospray Mass Spectrometry, Martin Paine, Phillip Barker, Shane A. Maclaughlin, Todd W. Mitchell, Stephen J. Blanksby
Stephen Blanksby
Rationale: Polymer-based surface coatings in outdoor applications experience accelerated degradation due to exposure to solar radiation, oxygen and atmospheric pollutants. These deleterious agents cause undesirable changes to the polymers aesthetic and mechanical properties reducing its lifetime. The use of antioxidants such as hindered amine light stabilisers (HALS) retard these degradative processes, however, mechanisms for HALS action and polymer degradation are poorly understood. Methods: Detection of the hindered amine light stabiliser (HALS) TINUVIN®123 (bis (1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate) and the polymer degradation products directly from a polyester-based coil coating was achieved by liquid extraction surface analysis (LESA) coupled to a triple quadrupole QTRAP® …
Human Lens Lipids Differ Markedly From Those Of Commonly Used Experimental Animals, Jane Deeley, Todd W. Mitchell, Xiaojia Wei, Jurgen Korth, Jessica Hughes, Stephen J. Blanksby, Roger J. Truscott
Human Lens Lipids Differ Markedly From Those Of Commonly Used Experimental Animals, Jane Deeley, Todd W. Mitchell, Xiaojia Wei, Jurgen Korth, Jessica Hughes, Stephen J. Blanksby, Roger J. Truscott
Stephen Blanksby
Electrospray ionisation tandem mass spectrometry has allowed the unambiguous identification andquantification of individual lens phospholipids in human and six animal models. Using this approach ca. 100unique phospholipids have been characterised. Parallel analysis of the same lens extracts by a novel directinsertionelectron-ionization technique found the cholesterol content of human lenses to be significantlyhigher (ca. 6 times) than lenses from the other animals.The most abundant phospholipids in all the lenses examined were choline-containing phospholipids. In rat,mouse, sheep, cow, pig and chicken, thesewere present largely as phosphatidylcholines, in contrast 66% of thetotal phospholipid in Homo sapienswas sphingomyelin, with the most abundant being dihydrosphingomyelins,in …
Reactions Of Simple And Peptidic Alpha-Carboxylate Radical Anions With Dioxygen In The Gas Phase, Tony Ly, Benjamin B. Kirk, Pramesh I. Hettiarachchi, Berwyck L. Poad, Adam J. Trevitt, Gabriel Da Silva, Stephen J. Blanksby
Reactions Of Simple And Peptidic Alpha-Carboxylate Radical Anions With Dioxygen In The Gas Phase, Tony Ly, Benjamin B. Kirk, Pramesh I. Hettiarachchi, Berwyck L. Poad, Adam J. Trevitt, Gabriel Da Silva, Stephen J. Blanksby
Stephen Blanksby
α-Carboxylate radical anions are potential reactive intermediates in the free radical oxidation of biological molecules (e.g., fatty acids, peptides and proteins). We have synthesised well-defined α-carboxylate radical anions in the gas phase by UV laser photolysis of halogenated precursors in an ion-trap mass spectrometer. Reactions of isolated acetate (CH2CO 2-) and 1-carboxylatobutyl (CH3CH 2CH2CHCO2-) radical anions with dioxygen yield carbonate (CO3-) radical anions and this chemistry is shown to be a hallmark of oxidation in simple and alkyl-substituted cross-conjugated species. Previous solution phase studies have shown that Cα-radicals in peptides, formed from free radical damage, combine with dioxygen to form …