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Full-Text Articles in Medicine and Health Sciences
Rapid Profiling Of Laser-Induced Photochemistry In Single Microdroplets Using Mass Spectrometry, Phillip J. Tracey, Bartholomew S. Vaughn, Brendon J. Roberts, Berwyck L. J Poad, Adam J. Trevitt
Rapid Profiling Of Laser-Induced Photochemistry In Single Microdroplets Using Mass Spectrometry, Phillip J. Tracey, Bartholomew S. Vaughn, Brendon J. Roberts, Berwyck L. J Poad, Adam J. Trevitt
Adam Trevitt
Rapid assessment of laser-induced photochemistry in single microdroplets is afforded by on-demand microdroplet generation coupled to a commercial ion-trap mass spectrometer. Single microdroplets (diameter 50 μm, 65 pL) fall on a steel needle held at +2 kV where they subsequently form a spray that is directed toward the inlet of an ion-trap mass spectrometer. It is demonstrated that single microdroplet mass spectra are recordable, one at a time, for methanol droplets containing 100 μM 4-iodoaniline. Extending on this, to probe laser-initiated photochemistry in single picoliter volumes, a UV laser pulse is timed to intercept the droplet before hitting the needle. …
Product Branching Fractions Of The Ch + Propene Reaction From Synchrotron Photoionization Mass Spectrometry, Adam J. Trevitt, Matthew B. Prendergast, Fabien Goulay, John D. Savee, David L. Osborn, Craig A. Taatjes, Stephen R. Leone
Product Branching Fractions Of The Ch + Propene Reaction From Synchrotron Photoionization Mass Spectrometry, Adam J. Trevitt, Matthew B. Prendergast, Fabien Goulay, John D. Savee, David L. Osborn, Craig A. Taatjes, Stephen R. Leone
Adam Trevitt
The CH(X2Π) + propene reaction is studied in the gas phase at 298 K and 4 Torr (533.3 Pa) using VUV synchrotron photoionization mass spectrometry. The dominant product channel is the formation of C4H6 (m/z 54) + H. By fitting experimental photoionization spectra to measured spectra of known C4H6 isomers, the following relative branching fractions are obtained: 1,3-butadiene (0.63 ± 0.13), 1,2-butadiene (0.25 ± 0.05), and 1-butyne (0.12 ± 0.03) with no detectable contribution from 2-butyne. The CD + propene reaction is also studied and two product channels are observed that correspond to C4H6 (m/z 54) + D and C4H5D …
Photodissociation Of Tempo-Modified Peptides: New Approaches To Radical-Directed Dissociation Of Biomolecules, David L. Marshall, Christopher S. Hansen, Adam J. Trevitt, Han Bin Oh, Stephen J. Blanksby
Photodissociation Of Tempo-Modified Peptides: New Approaches To Radical-Directed Dissociation Of Biomolecules, David L. Marshall, Christopher S. Hansen, Adam J. Trevitt, Han Bin Oh, Stephen J. Blanksby
Adam Trevitt
Radical-directed dissociation of gas phase ions is emerging as a powerful and complementary alternative to traditional tandem mass spectrometric techniques for biomolecular structural analysis. Previous studies have identified that coupling of 2-[(2,2,6,6-tetramethylpiperidin-1-oxyl)methyl]benzoic acid (TEMPO-Bz) to the N-terminus of a peptide introduces a labile oxygen–carbon bond that can be selectively activated upon collisional activation to produce a radical ion. Here we demonstrate that structurally-defined peptide radical ions can also be generated upon UV laser photodissociation of the same TEMPO-Bz derivatives in a linear ion-trap mass spectrometer. When subjected to further mass spectrometric analyses, the radical ions formed by a single laser …
Observation Of Nondegenerate Cavity Modes For A Distorted Cavity Modes For A Distorted Polystyrene Microsphere, Adam J. Trevitt, Philip J. Wearne, Evan J. Bieske, Michael D. Schuder
Observation Of Nondegenerate Cavity Modes For A Distorted Cavity Modes For A Distorted Polystyrene Microsphere, Adam J. Trevitt, Philip J. Wearne, Evan J. Bieske, Michael D. Schuder
Adam Trevitt
Nondegenerate azimuthal morphology-dependent resonances are observed for a distorted, fluorescently labeled polystyrene microsphere levitated in a quadrupole ion trap. Modeling the individual resonances by using perturbation theory allows a determination of quadrupole and octupole distortion parameters. The particle’s shape changes slowly over the course of the measurement and eventually becomes spherical. The morphological changes are facilitated by laser heating of the particle above the polystyrene glass transition temperature. We demonstrate a method of transforming a trapped particle to a sphere and rendering its azimuthal modes degenerate.
Isomer-Specific Product Detection Of Gas-Phase Xylyl Radical Rearrangement And Decomposition Using Vuv Synchrotron Photoionization, Patrick Hemberger, Adam J. Trevitt, Thomas Gerber, Edward Ross, Gabriel Da Silva
Isomer-Specific Product Detection Of Gas-Phase Xylyl Radical Rearrangement And Decomposition Using Vuv Synchrotron Photoionization, Patrick Hemberger, Adam J. Trevitt, Thomas Gerber, Edward Ross, Gabriel Da Silva
Adam Trevitt
Xylyl radicals are intermediates in combustion processes since their parent molecules, xylenes, are present as fuel additives. In this study we report on the photoelectron spectra of the three isomeric xylyl radicals and the subsequent decomposition reactions of the o-xylyl radical, generated in a tubular reactor and probed by mass selected threshold photoelectron spectroscopy and VUV synchrotron radiation. Franck-Condon simulations are applied to augment the assignment of elusive species. Below 1000 K, o-xylyl radicals decompose by hydrogen atom loss to form closed-shell o-xylylene, which equilibrates with benzocyclobutene. At higher temperatures relevant to combustion engines, o-xylylene generates styrene in a multistep …
Hydroxyl Radical Formation In The Gas Phase Oxidation Of Distonic 2-Methylphenyl Radical Cations, Matthew Prendergast, Phillip A. Cooper, Benjamin B. Kirk, Gabriel Da Silva, Stephen J. Blanksby, Adam J. Trevitt
Hydroxyl Radical Formation In The Gas Phase Oxidation Of Distonic 2-Methylphenyl Radical Cations, Matthew Prendergast, Phillip A. Cooper, Benjamin B. Kirk, Gabriel Da Silva, Stephen J. Blanksby, Adam J. Trevitt
Adam Trevitt
The reactions of distonic 4-(N,N,N-trimethylammonium)-2-methylphenyl and 5-(N,N,N-trimethylammonium)-2-methylphenyl radical cations (m/z 149) with O 2 are studied in the gas phase using ion-trap mass spectrometry. Photodissociation (PD) of halogenated precursors gives rise to the target distonic charge-tagged methylphenyl radical whereas collision-induced dissociation (CID) is found to produce unreactive radical ions. The PD generated distonic radicals, however, react rapidly with O2 to form [M + O2]•+ and [M + O2 - OH]•+ ions, detected at m/z 181 and m/z 164, respectively. Quantum chemical calculations using G3SX(MP3) and M06-2X theories are deployed to examine key decomposition pathways of the 5-(N,N,N-trimethylammonium)-2-methylphenylperoxyl radical and rationalise …
Characterisation Of The Ionic Products Arising From Electron Photodetachment Of Simple Dicarboxylate Dianions, Benjamin B. Kirk, Adam J. Trevitt, Berwyck L. Poad, Stephen J. Blanksby
Characterisation Of The Ionic Products Arising From Electron Photodetachment Of Simple Dicarboxylate Dianions, Benjamin B. Kirk, Adam J. Trevitt, Berwyck L. Poad, Stephen J. Blanksby
Adam Trevitt
Much of what we currently understand about the structure and energetics of multiply charged anions in the gas phase is derived from the measurement of photoelectron spectra of simple dicarboxylate dianions. Here we have employed a modified linear ion-trap mass spectrometer to undertake complementary investigations of the ionic products resulting from laser-initiated electron photodetachment of two model dianions. Electron photodetachment (ePD) of the [M-2H]2- dianions formed from glutaric and adipic acid were found to result in a significant loss of ion signal overall, which is consistent with photoelectron studies that report the emission of slow secondary electrons (Xing et al., …
Rapid Differentiation Of Isomeric Lipids By Photodissociation Mass Spectrometry Of Fatty Acid Derivatives, Huong T. Pham, Adam J. Trevitt, Todd W. Mitchell, Stephen J. Blanksby
Rapid Differentiation Of Isomeric Lipids By Photodissociation Mass Spectrometry Of Fatty Acid Derivatives, Huong T. Pham, Adam J. Trevitt, Todd W. Mitchell, Stephen J. Blanksby
Adam Trevitt
RATIONALE Both traditional electron ionization and electrospray ionization tandem mass spectrometry have demonstrated limitations in the unambiguous identification of fatty acids. In the former case, high electron energies lead to extensive dissociation of the radical cations from which little specific structural information can be obtained. In the latter, conventional collision-induced dissociation (CID) of even-electron ions provides little intra-chain fragmentation and thus few structural diagnostics. New approaches that harness the desirable features of both methods, namely radical-driven dissociation with discrete energy deposition, are thus required. METHODS Herein we describe the derivatization of a structurally diverse suite of fatty acids as 4-iodobenzyl …
Ultraviolet Action Spectroscopy Of Iodine Labeled Peptides And Proteins In The Gas Phase, Benjamin B. Kirk, Adam J. Trevitt, Stephen J. Blanksby, Yuanqi Tao, Benjamin N. Moore, Ryan Julian
Ultraviolet Action Spectroscopy Of Iodine Labeled Peptides And Proteins In The Gas Phase, Benjamin B. Kirk, Adam J. Trevitt, Stephen J. Blanksby, Yuanqi Tao, Benjamin N. Moore, Ryan Julian
Adam Trevitt
Structural investigations of large biomolecules in the gas phase are challenging. Herein, it is reported that action spectroscopy taking advantage of facile carbon-iodine bond dissociation can be used to examine the structures of large molecules, including whole proteins. Iodotyrosine serves as the active chromophore, which yields distinctive spectra depending on the solvation of the side chain by the remainder of the molecule. Isolation of the chromophore yields a double featured peak at 290 nm, which becomes a single peak with increasing solvation. Deprotonation of the side chain also leads to reduced apparent intensity and broadening of the action spectrum. The …
Does Addition Of No2 To Carbon-Centered Radicals Yield Rono Or Rno2? An Investigation Using Distonic Radical Ions, Benjamin B. Kirk, Adam J. Trevitt, Stephen J. Blanksby
Does Addition Of No2 To Carbon-Centered Radicals Yield Rono Or Rno2? An Investigation Using Distonic Radical Ions, Benjamin B. Kirk, Adam J. Trevitt, Stephen J. Blanksby
Adam Trevitt
Nitrogen dioxide is used as a "radical scavenger" to probe the position of carbon-centered radicals within complex radical ions in the gas phase. As with analogous neutral radical reactions, this addition results in formation of an [M + NO2](+) adduct, but the structural identity of this species remains ambiguous. Specifically, the question remains: do such adducts have a nitro-(RNO2) or nitrosoxy-(RONO) moiety, or are both isomers present in the adduct population? In order to elucidate the products of such reactions, we have prepared and isolated three distonic phenyl radical cations and observed their reactions with nitrogen dioxide in the gas …
Product Detection Of The Ch Radical Reaction With Acetaldehyde, Fabien Goulay, Adam Trevitt, John Savee, Jordy Bouwman, David Osborn, Craig Taatjes, Kevin Wilson, Stephen Leone
Product Detection Of The Ch Radical Reaction With Acetaldehyde, Fabien Goulay, Adam Trevitt, John Savee, Jordy Bouwman, David Osborn, Craig Taatjes, Kevin Wilson, Stephen Leone
Adam Trevitt
The reaction of the methylidyne radical (CH) with acetaldehyde (CH3CHO) is studied at room temperature and at a pressure of 4 Torr (533.3 Pa) using a multiplexed photoionization mass spectrometer coupled to the tunable vacuum ultraviolet synchrotron radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory. The CH radicals are generated by 248 nm multiphoton photolysis of CHBr3 and react with acetaldehyde in an excess of helium and nitrogen gas flow. Five reaction exit channels are observed corresponding to elimination of methylene (CH2), elimination of a formyl radical (HCO), elimination of carbon monoxide (CO), elimination of a methyl …
Uv Photodissociation Action Spectroscopy Of Haloanilinium Ions In A Linear Quadrupole Ion Trap Mass Spectrometer, Christopher S. Hansen, Benjamin B. Kirk, Stephen J. Blanksby, Richard A. J O'Hair, Adam J. Trevitt
Uv Photodissociation Action Spectroscopy Of Haloanilinium Ions In A Linear Quadrupole Ion Trap Mass Spectrometer, Christopher S. Hansen, Benjamin B. Kirk, Stephen J. Blanksby, Richard A. J O'Hair, Adam J. Trevitt
Adam Trevitt
UV-vis photodissociation action spectroscopy is becoming increasingly prevalent because of advances in, and commercial availability of, ion trapping technologies and tunable laser sources. This study outlines in detail an instrumental arrangement, combining a commercial ion-trap mass spectrometer and tunable nanosecond pulsed laser source, for performing fully automated photodissociation action spectroscopy on gas-phase ions. The components of the instrumentation are outlined, including the optical and electronic interfacing, in addition to the control software for automating the experiment and performing online analysis of the spectra. To demonstrate the utility of this ensemble, the photodissociation action spectra of 4-chloroanilinium, 4-bromoanilinium, and 4-iodoanilinium cations …
Formation Of Dimethylketene And Methacrolein By Reaction Of The Ch Radical With Acetone, Fabien Goulay, Adeeb Derakhshan, Eamonn Maher, Adam J. Trevitt, John D. Savee, Adam M. Scheer, David L. Osborn, Craig A. Taatjes
Formation Of Dimethylketene And Methacrolein By Reaction Of The Ch Radical With Acetone, Fabien Goulay, Adeeb Derakhshan, Eamonn Maher, Adam J. Trevitt, John D. Savee, Adam M. Scheer, David L. Osborn, Craig A. Taatjes
Adam Trevitt
The reaction of the methylidyne radical (CH) with acetone ((CH3)2CO) is studied at room temperature and at a pressure of 4 Torr (533.3 Pa) using a multiplexed photoionization mass spectrometer coupled to the tunable vacuum ultraviolet synchrotron radiation of the Advanced Light Source at Lawrence Berkeley National Laboratory. The CH radicals are generated by 248 nm multiphoton photolysis of bromoform and react with acetone in an excess of helium and nitrogen gas flow. The main observed reaction exit channel is elimination of a hydrogen atom to form C4H6O isomers. Analysis of photoionization spectra identifies dimethylketene and methacrolein as the only …
Isolation And Characterization Of Charge-Tagged Phenylperoxyl Radicals In The Gas Phase: Direct Evidence For Products And Pathways In Low Temperature Benzene Oxidation, Benjamin Kirk, David Harman, Hilkka Kenttamaa, Adam Trevitt, Stephen Blanksby
Isolation And Characterization Of Charge-Tagged Phenylperoxyl Radicals In The Gas Phase: Direct Evidence For Products And Pathways In Low Temperature Benzene Oxidation, Benjamin Kirk, David Harman, Hilkka Kenttamaa, Adam Trevitt, Stephen Blanksby
Adam Trevitt
The phenylperoxyl radical has long been accepted as a critical intermediate in the oxidation of benzene and an archetype for arylperoxyl radicals in combustion and atmospheric chemistry. Despite being central to many contemporary mechanisms underpinning these chemistries, reports of the direct detection or isolation of phenylperoxyl radicals are rare and there is little experimental evidence connecting this intermediate with expected product channels. We have prepared and isolated two charge-tagged phenyl radical models in the gas phase [i.e., 4-(N,N,N-trimethylammonium)phenyl radical cation and 4-carboxylatophenyl radical anion] and observed their reactions with dioxygen by ion-trap mass spectrometry. Measured reaction rates show good agreement …