1
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Uleanya KO, Anstöter CS, Dessent CEH. Photodissociative decay pathways of the flavin mononucleotide anion and its complexes with tryptophan and glutamic acid. Phys Chem Chem Phys 2023; 25:30697-30707. [PMID: 37934009 DOI: 10.1039/d3cp04359b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
Flavin mononucleotide (FMN) is a highly versatile biological chromophore involved in a range of biochemical pathways including blue-light sensing proteins and the control of circadian rhythms. Questions exist about the effect of local amino acids on the electronic properties and photophysics of the chromophore. Using gas-phase anion laser photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (3.1-5.7 eV) and accompanying photodissociative decay pathways of the native deprotonated form of FMN, i.e. [FMN-H]- complexed with the amino acids tryptophan (TRP) and glutamic acid (GLU), i.e. [FMN-H]-·TRP and [FMN-H]-·GLU, to investigate the extent to which these amino acids perturb the electronic properties and photodynamics of the [FMN-H]- chromophore. The overall photodepletion profiles of [FMN-H]-·TRP and [FMN-H]-·GLU are similar to that of the monomer, revealing that amino acid complexation occurs without significant spectral shifting of the [FMN-H]- electronic excitations over this region. Both [FMN-H]-·TRP and [FMN-H]-·GLU are observed to decay by non-statistical photodecay pathways, although the behaviour of [FMN-H]-·TRP is closer to statistical fragmentation. Long-lived FMN excited states (triplet) are therefore relatively quenched when TRP binds to [FMN-H]-. Importantly, we find that [FMN-H]-, [FMN-H]-·TRP and [FMN-H]-·GLU all decay predominantly via electron detachment following photoexcitation of the flavin chromophore, with amino acid complexation appearing not to inhibit this decay channel. The strong propensity for electron detachment is attributed to excited-state proton transfer within FMN, with proton transfer from a ribose alcohol to the phosphate preceding electron detachment.
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Affiliation(s)
- Kelechi O Uleanya
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
| | - Cate S Anstöter
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
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2
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Tureček F. UV-vis spectroscopy of gas-phase ions. MASS SPECTROMETRY REVIEWS 2023; 42:206-226. [PMID: 34392556 DOI: 10.1002/mas.21726] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
Photodissociation action spectroscopy has made a great progress in expanding investigations of gas-phase ion structures. This review deals with aspects of gas-phase ion electronic excitations that result in wavelength-dependent dissociation and light emission via fluorescence, chiefly covering the ultraviolet and visible regions of the spectrum. The principles are briefly outlined and a few examples of instrumentation are presented. The main thrust of the review is to collect and selectively present applications of UV-vis action spectroscopy to studies of stable gas-phase ion structures and combinations of spectroscopy with ion mobility, collision-induced dissociation, and ion-ion reactions leading to the generation of reactive intermediates and electronic energy transfer.
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Affiliation(s)
- František Tureček
- Department of Chemistry, University of Washington, Seattle, Washington, USA
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3
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Oluwatoba DS, Islam MF, Som B, Sindt AJ, Smith MD, Shimizu LS, Do TD. Evaluating the Effects of Metal Adduction and Charge Isomerism on Ion-Mobility Measurements using m-Xylene Macrocycles as Models. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:840-850. [PMID: 35471025 DOI: 10.1021/jasms.2c00033] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Gas-phase ion-mobility spectrometry provides a unique platform to study the effect of mobile charge(s) or charge location on collisional cross section and ion separation. Here, we evaluate the effects of cation/anion adduction in a series of xylene and pyridyl macrocycles that contain ureas and thioureas. We explore how zinc binding led to unexpected deprotonation of the thiourea macrocyclic host in positive polarity ionization and subsequently how charge isomerism due to cation (zinc metal) and anion (chloride counterion) adduction or proton competition among acceptors can affect the measured collisional cross sections in helium and nitrogen buffer gases. Our approach uses synthetic chemistry to design macrocycle targets and a combination of ion-mobility spectrometry mass spectrometry experiments and quantum mechanics calculations to characterize their structural properties. We demonstrate that charge isomerism significantly improves ion-mobility resolution and allows for determination of the metal binding mechanism in metal-inclusion macrocyclic complexes. Additionally, charge isomers can be populated in molecules where individual protons are shared between acceptors. In these cases, interactions via drift gas collisions magnify the conformational differences. Finally, for the macrocyclic systems we report here, charge isomers are observed in both helium and nitrogen drift gases with similar resolution. The separation factor does not simply increase with increasing drift gas polarizability. Our study sheds light on important properties of charge isomerism and offers strategies to take advantage of this phenomenon in analytical separations.
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Affiliation(s)
- Damilola S Oluwatoba
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Md Faizul Islam
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Bozumeh Som
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
- Department of Chemistry, University of Ghana, P.O. Box LG 56, Legon, Accra, Ghana
| | - Ammon J Sindt
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Mark D Smith
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Linda S Shimizu
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Thanh D Do
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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4
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Hirata K, Haddad F, Dopfer O, Ishiuchi SI, Fujii M. Collision-assisted stripping for determination of microsolvation-dependent protonation sites in hydrated clusters by cryogenic ion trap infrared spectroscopy: the case of benzocaineH +(H 2O) n. Phys Chem Chem Phys 2022; 24:5774-5779. [PMID: 35199812 DOI: 10.1039/d1cp05762f] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The protonation site of molecules can be varied by their surrounding environment. Gas-phase studies, including the popular techniques of infrared spectroscopy and ion mobility spectrometry, are a powerful tool for the determination of protonation sites in solvated clusters but often suffer from inherent limits for larger hydrated clusters. Here, we present collision-assisted stripping infrared (CAS-IR) spectroscopy as a new technique to overcome these problems and apply it in a proof-of-principle experiment to hydrated clusters of protonated benzocaine (H+BC), which shows protonation-site switching depending on the degree of hydration. The most stable protomer of H+BC in the gas phase (O-protonated) is interconverted into its most stable protomer in aqueous solution (N-protonated) upon hydration with three water molecules. CAS-IR spectroscopy enables us to unambiguously assign protonation sites and quantitatively determine the relative abundance of various protomers.
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Affiliation(s)
- Keisuke Hirata
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan. .,Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.,Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovation Research, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, 4259, Yokohama, 226-8503, Japan.
| | - Fuad Haddad
- Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin 10623, Germany
| | - Otto Dopfer
- Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovation Research, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, 4259, Yokohama, 226-8503, Japan. .,Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstrasse 36, Berlin 10623, Germany
| | - Shun-Ichi Ishiuchi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan. .,Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.,Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovation Research, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, 4259, Yokohama, 226-8503, Japan.
| | - Masaaki Fujii
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, 226-8503, Japan. .,Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovation Research, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, 4259, Yokohama, 226-8503, Japan. .,School of Life Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8503, Japan
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5
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Ucur B, Maccarone AT, Ellis SR, Blanksby SJ, Trevitt AJ. Solvent-Mediated Proton-Transfer Catalysis of the Gas-Phase Isomerization of Ciprofloxacin Protomers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:347-354. [PMID: 35014802 DOI: 10.1021/jasms.1c00331] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Understanding how neutral molecules become protonated during positive-ion electrospray ionization (ESI) mass spectrometry is critically important to ensure analytes can be efficiently ionized, detected, and unambiguously identified. The ESI solvent is one of several parameters that can alter the dominant site of protonation in polyfunctional molecules and thus, in turn, can significantly change the collision-induced dissociation (CID) mass spectra relied upon for compound identification. Ciprofloxacin─a common fluoroquinolone antibiotic─is one such example whereby positive-ion ESI can result in gas-phase [M + H]+ ions protonated at either the keto-oxygen or the piperazine-nitrogen. Here, we demonstrate that these protonation isomers (or protomers) of ciprofloxacin can be resolved by differential ion mobility spectrometry and give rise to distinctive CID mass spectra following both charge-directed and charge-remote mechanisms. Interaction of mobility-selected protomers with methanol vapor (added via the throttle gas supply) was found to irreversibly convert the piperazine N-protomer to the keto-O-protomer. This methanol-mediated proton-transport catalysis is driven by the overall exothermicity of the reaction, which is computed to favor the O-protomer by 93 kJ mol-1 (in the gas phase). Conversely, gas phase interactions of mobility-selected ions with acetonitrile vapor selectively depletes the N-protomer ion signal as formation of stable [M + H + CH3CN]+ cluster ions skews the apparent protomer population ratio, as the O-protomer is unaffected. These findings provide a mechanistic basis for tuning protomer populations to ensure faithful characterization of multifunctional molecules by tandem mass spectrometry.
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Affiliation(s)
- Boris Ucur
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Alan T Maccarone
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Shane R Ellis
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
- Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility and School of Chemistry and Physics, Queensland University of Technology, Brisbane 4001, Australia
| | - Adam J Trevitt
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
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6
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Marlton SJP, Trevitt A. Laser Photodissocation, Action Spectroscopy and Mass Spectrometry Unite to Detect and Separate Isomers. Chem Commun (Camb) 2022; 58:9451-9467. [DOI: 10.1039/d2cc02101c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The separation and detection of isomers remains a challenge for many areas of mass spectrometry. This article highlights laser photodissociation and ion mobility strategies that have been deployed to tackle...
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7
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Wong NGK, Rhodes C, Dessent CEH. Photodegradation of Riboflavin under Alkaline Conditions: What Can Gas-Phase Photolysis Tell Us about What Happens in Solution? Molecules 2021; 26:6009. [PMID: 34641554 PMCID: PMC8512791 DOI: 10.3390/molecules26196009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/25/2021] [Accepted: 09/30/2021] [Indexed: 11/16/2022] Open
Abstract
The application of electrospray ionisation mass spectrometry (ESI-MS) as a direct method for detecting reactive intermediates is a technique of developing importance in the routine monitoring of solution-phase reaction pathways. Here, we utilise a novel on-line photolysis ESI-MS approach to detect the photoproducts of riboflavin in aqueous solution under mildly alkaline conditions. Riboflavin is a constituent of many food products, so its breakdown processes are of wide interest. Our on-line photolysis setup allows for solution-phase photolysis to occur within a syringe using UVA LEDs, immediately prior to being introduced into the mass spectrometer via ESI. Gas-phase photofragmentation studies via laser-interfaced mass spectrometry of deprotonated riboflavin, [RF - H]-, the dominant solution-phase species under the conditions of our study, are presented alongside the solution-phase photolysis. The results obtained illustrate the extent to which gas-phase photolysis methods can inform our understanding of the corresponding solution-phase photochemistry. We determine that the solution-phase photofragmentation observed for [RF - H]- closely mirrors the gas-phase photochemistry, with the dominant m/z 241 condensed-phase photoproduct also being observed in gas-phase photodissociation. Further gas-phase photoproducts are observed at m/z 255, 212, and 145. The value of exploring both the gas- and solution-phase photochemistry to characterise photochemical reactions is discussed.
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Affiliation(s)
| | | | - Caroline E. H. Dessent
- Department of Chemistry, University of York, Heslington YO10 5DD, UK; (N.G.K.W.); (C.R.)
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8
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Ziegler P, Pelc A, Arthur-Baidoo E, Ameixa J, Ončák M, Denifl S. Negative ion formation and fragmentation upon dissociative electron attachment to the nicotinamide molecule. RSC Adv 2021; 11:32425-32434. [PMID: 35495526 PMCID: PMC9041917 DOI: 10.1039/d1ra06083j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 09/13/2021] [Indexed: 12/20/2022] Open
Abstract
Nicotinamide (C6H6N2O) is a biologically relevant molecule. This compound has several important roles related to the anabolic and metabolic processes that take place in living organisms. It is also used as a radiosensitizer in tumor therapy. As a result of the interaction of high-energy radiation with matter, low-energy electrons are also released, which can also interact with other molecules, forming several types of ions. In the present investigation, dissociative electron attachment to C6H6N2O has been studied in a crossed electron-molecular beams experiment in the electron energy range of about 0-15 eV. In the experiment, six anionic species were detected: C6H5N2O-, C5H4N-, NCO-, O-/NH2 -, and CN-, with NCO- being the most prominent anion. We also provide detailed computational results regarding the energetic thresholds and pathways of the respective dissociative electron attachment (DEA) channels. The experimental results are compared with the theoretical ones and on this basis, the possible DEA reactions for the formation of anions at a given resonance energy were assigned as well as the generation of neutrals fragments such as pyridine and its several derivatives and radicals are predicted. The pyridine ring seems to stay intact during the DEA process.
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Affiliation(s)
- Patrick Ziegler
- Institute for Ion Physics and Applied Physics, University of Innsbruck Technikerstrasse 25 6020 Innsbruck Austria
| | - Andrzej Pelc
- Maria Curie-Skłodowska University, Department of Biophysics, Mass Spectrometry Laboratory Pl. M. C.-Skłodowskiej 1 20-031 Lublin Poland
| | - Eugene Arthur-Baidoo
- Institute for Ion Physics and Applied Physics, University of Innsbruck Technikerstrasse 25 6020 Innsbruck Austria
| | - Joao Ameixa
- Institute for Ion Physics and Applied Physics, University of Innsbruck Technikerstrasse 25 6020 Innsbruck Austria .,Centre of Physics and Technological Research, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa 2829-516 Caparica Portugal
| | - Milan Ončák
- Institute for Ion Physics and Applied Physics, University of Innsbruck Technikerstrasse 25 6020 Innsbruck Austria
| | - Stephan Denifl
- Institute for Ion Physics and Applied Physics, University of Innsbruck Technikerstrasse 25 6020 Innsbruck Austria
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9
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Wong NK, Rankine CD, Dessent CEH. Measurement of the Population of Electrosprayed Deprotomers of Coumaric Acids Using UV-Vis Laser Photodissociation Spectroscopy. J Phys Chem A 2021; 125:6703-6714. [PMID: 34342453 PMCID: PMC8389988 DOI: 10.1021/acs.jpca.1c04880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/08/2021] [Indexed: 01/05/2023]
Abstract
The measurement of deprotonation sites in multifunctional molecules following electrospray ionization is important to better inform a wide range of spectroscopic and photophysical studies that use electrospray to prepare molecular species for study in the gas phase. We demonstrate that low-resolution UV-vis laser photodissociation spectroscopy can be applied in situ to identify the deprotomers of three coumaric acids, trans-para-coumaric acid (CMA), trans-caffeic acid (CA), and trans-ferulic acid (FA), formed via electrospray. Electronic absorption spectra of the deprotonated coumaric acids are recorded via photodepletion and photofragmentation following electrospray from solutions of ethanol and acetonitrile. By comparing the experimental spectra to wave function theory calculations, we are able to confirm the presence of phenoxide and carboxylate deprotomers upon electrospray for all three coumaric acids, when sprayed from both protic and aprotic solvents. Ratios of the phenoxide:carboxylate deprotomers are obtained by generating summed theoretical absorption spectra that reproduce the experimental spectra. We find that choice of electrospray solvent has little effect on the ratio of deprotomers obtained for deprotonated CMA and CA but has a greater impact for FA. Our results are in excellent agreement with previous work conducted on deprotonated CMA using IR spectroscopy and demonstrate that UV photodissociation spectroscopy of electrosprayed ions has potential as a diagnostic tool for identifying deprotomeric species.
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Affiliation(s)
- Natalie
G. K. Wong
- Department
of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
| | - Conor D. Rankine
- School
of Natural and Environmental Sciences, Newcastle
University, Newcastle-upon-Tyne NE1 7RU, U.K.
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10
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Marshall DL, Menzel JP, McKinnon BI, Blinco JP, Trevitt AJ, Barner-Kowollik C, Blanksby SJ. Laser Photodissociation Action Spectroscopy for the Wavelength-Dependent Evaluation of Photoligation Reactions. Anal Chem 2021; 93:8091-8098. [PMID: 34019383 DOI: 10.1021/acs.analchem.1c01584] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nitrile imine-mediated tetrazole-ene cycloaddition is a widely used class of photoligation. Optimizing the reaction outcome requires detailed knowledge of the tetrazole photoactivation profile, which can only partially be ascertained from absorption spectroscopy, or otherwise involves laborious reaction monitoring in solution. Photodissociation action spectroscopy (PDAS) combines the advantages of optical spectroscopy and mass spectrometry in that only absorption events resulting in a mass change are recorded, thus revealing the desired wavelength dependence of product formation. Moreover, the sensitivity and selectivity afforded by the mass spectrometer enable reliable assessment of the photodissociation profile even on small amounts of crude material, thus accelerating the design and synthesis of next-generation substrates. Using this workflow, we demonstrate that the photodissociation onset for nitrile imine formation is red-shifted by ca. 50 nm with a novel N-ethylcarbazole derivative relative to a phenyl-substituted archetype. Benchmarked against solution-phase tunable laser experiments and supported by quantum chemical calculations, these discoveries demonstrate that PDAS is a powerful tool for rapidly screening the efficacy of new substrates in the quest toward efficient visible light-triggered ligation for biological applications.
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Affiliation(s)
- David L Marshall
- Central Analytical Research Facility, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.,Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
| | - Jan P Menzel
- Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.,School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
| | - Benjamin I McKinnon
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - James P Blinco
- Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.,School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
| | - Adam J Trevitt
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Christopher Barner-Kowollik
- Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.,School of Chemistry and Physics, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.,Centre for Materials Science, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
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11
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Marlton SJP, McKinnon BI, Hill NS, Coote ML, Trevitt AJ. Electrostatically Tuning the Photodissociation of the Irgacure 2959 Photoinitiator in the Gas Phase by Cation Binding. J Am Chem Soc 2021; 143:2331-2339. [PMID: 33427467 DOI: 10.1021/jacs.0c11978] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The low-lying electronic states of Irgacure 2959, a Norrish-type I photoinitiator, complexed with a single metal cation are investigated in the gas phase by photodissociation action spectroscopy. Analysis of the band shifts using quantum chemical calculations (TD-DFT and SCS-CC2) reveals the underlying influence of the charge on the key electronic energy levels. Since the cations (H+, Li+, Na+, K+, Zn2+, Ca2+, and Mg2+) bind at varying distances, the magnitude of the electric field at the center of the chromophore due to the cation is altered, and this shifts the electronic states by different amounts. Photodissociation action spectra of cation-Irg complexes show that absorption transitions to the first 1ππ* state are red-shifted with a magnitude proportional to the electric field strength (with red shifts >1 eV), and in most cases, the cation is essentially acting as a point charge. Calculations show that a neighboring 3nπ* state, a key state for the α-cleavage pathway, is destabilized (blue-shifted) by the orientated electric field. As such, if the 1ππ*-3nπ* energy gap is reduced, increased intersystem crossing rates are expected, resulting in higher yields of the desired radical photoproducts, and this is controlled by the orientated electric field arising from the cation.
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Affiliation(s)
- Samuel J P Marlton
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Benjamin I McKinnon
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Nicholas S Hill
- ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Michelle L Coote
- ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Adam J Trevitt
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
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12
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Lermyte F, Theisen A, O'Connor PB. Solution Condition-Dependent Formation of Gas-Phase Protomers of Alpha-Synuclein in Electrospray Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:364-372. [PMID: 33237779 DOI: 10.1021/jasms.0c00373] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
One of the main characteristics of biomolecular ions in mass spectrometry is their net charge, and a range of approaches exist to either increase or decrease this quantity in the gas phase. In the context of small molecules, it is well known that, in addition to the charge state, the charge site also has a profound effect on an ion's gas-phase behavior; however, this effect has been far less explored for peptides and intact proteins. Methods exist to determine charge sites of protein ions, and others have observed that the interplay of electrostatic repulsion and inherent basicity leads to different sites gaining or losing a charge depending on the total net charge. Here, we report two distinct protonation site isomers ("protomers") of α-synuclein occurring at the same charge state. The protomers showed important differences in their gas-phase fragmentation behavior and were furthermore distinguishable by ion mobility spectrometry. One protomer was produced under standard electrospray conditions, while the other was observed after addition of 10% dimethyl sulfoxide to the protein solution. Charge sites for both protomers were determined using ultraviolet photodissociation.
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Affiliation(s)
- Frederik Lermyte
- Department of Chemistry, Technical University of Darmstadt, 64287 Darmstadt, Germany
- School of Engineering, University of Warwick, Coventry CV4 7AL, U.K
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Alina Theisen
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Peter B O'Connor
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
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13
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Furlan C, Berenbeim JA, Dessent CEH. Photoproducts of the Photodynamic Therapy Agent Verteporfin Identified via Laser Interfaced Mass Spectrometry. Molecules 2020; 25:molecules25225280. [PMID: 33198255 PMCID: PMC7696214 DOI: 10.3390/molecules25225280] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/08/2020] [Accepted: 11/09/2020] [Indexed: 12/12/2022] Open
Abstract
Verteporfin, a free base benzoporphyrin derivative monoacid ring A, is a photosensitizing drug for photodynamic therapy (PDT) used in the treatment of the wet form of macular degeneration and activated by red light of 689 nm. Here, we present the first direct study of its photofragmentation channels in the gas phase, conducted using a laser interfaced mass spectrometer across a broad photoexcitation range from 250 to 790 nm. The photofragmentation channels are compared with the collision-induced dissociation (CID) products revealing similar dissociation pathways characterized by the loss of the carboxyl and ester groups. Complementary solution-phase photolysis experiments indicate that photobleaching occurs in verteporfin in acetonitrile; a notable conclusion, as photoinduced activity in Verteporfin was not thought to occur in homogenous solvent conditions. These results provide unique new information on the thermal break-down products and photoproducts of this light-triggered drug.
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14
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Observation of Enhanced Dissociative Photochemistry in the Non-Native Nucleobase 2-Thiouracil. Molecules 2020; 25:molecules25143157. [PMID: 32664261 PMCID: PMC7397253 DOI: 10.3390/molecules25143157] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/30/2020] [Accepted: 07/08/2020] [Indexed: 12/12/2022] Open
Abstract
We present the first study to measure the dissociative photochemistry of 2-thiouracil (2-TU), an important nucleobase analogue with applications in molecular biology and pharmacology. Laser photodissociation spectroscopy is applied to the deprotonated and protonated forms of 2-TU, which are produced in the gas-phase using electrospray ionization mass spectrometry. Our results show that the deprotonated form of 2-thiouracil ([2-TU-H]−) decays predominantly by electron ejection and hence concomitant production of the [2-TU-H]· free-radical species, following photoexcitation across the UVA-UVC region. Thiocyanate (SCN−) and a m/z 93 fragment ion are also observed as photodecay products of [2-TU-H]− but at very low intensities. Photoexcitation of protonated 2-thiouracil ([2-TU·H]+) across the same UVA-UVC spectral region produces the m/z 96 cationic fragment as the major photofragment. This ion corresponds to ejection of an HS· radical from the precursor ion and is determined to be a product of direct excited state decay. Fragment ions associated with decay of the hot ground state (i.e., the ions we would expect to observe if 2-thiouracil was behaving like UV-dissipating uracil) are observed as much more minor products. This behaviour is consistent with enhanced intersystem crossing to triplet excited states compared to internal conversion back to the ground state. These are the first experiments to probe the effect of protonation/deprotonation on thionucleobase photochemistry, and hence explore the effect of pH at a molecular level on their photophysical properties.
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15
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Marlton SJP, McKinnon BI, Ucur B, Bezzina JP, Blanksby SJ, Trevitt AJ. Discrimination between Protonation Isomers of Quinazoline by Ion Mobility and UV-Photodissociation Action Spectroscopy. J Phys Chem Lett 2020; 11:4226-4231. [PMID: 32368922 DOI: 10.1021/acs.jpclett.0c01009] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The influence of oriented electric fields on chemical reactivity and photochemistry is an area of increasing interest. Within a molecule, different protonation sites offer the opportunity to control the location of charge and thus orientation of electric fields. New techniques are thus needed to discriminate between protonation isomers in order to understand this effect. This investigation reports the UV-photodissociation action spectroscopy of two protonation isomers (protomers) of 1,3-diazanaphthalene (quinazoline) arising from protonation of a nitrogen at either the 1- or 3-position. It is shown that these protomers are separable by field-asymmetric ion mobility spectrometry (FAIMS) with confirmation provided by UV-photodissociation (PD) action spectroscopy. Vibronic features in the UVPD action spectra and computational input allow assignment of the origin transitions to the S1 and S5 states of both protomers. These experiments also provide vital benchmarks for protomer-specific calculations and examination of isomer-resolved reaction kinetics and thermodynamics.
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Affiliation(s)
- Samuel J P Marlton
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Benjamin I McKinnon
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Boris Ucur
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - James P Bezzina
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Stephen J Blanksby
- Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, Brisbane 4001, Australia
| | - Adam J Trevitt
- Molecular Horizons and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales 2522, Australia
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16
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Berenbeim JA, Wong NGK, Cockett MCR, Berden G, Oomens J, Rijs AM, Dessent CEH. Unravelling the Keto-Enol Tautomer Dependent Photochemistry and Degradation Pathways of the Protonated UVA Filter Avobenzone. J Phys Chem A 2020; 124:2919-2930. [PMID: 32208697 PMCID: PMC7168606 DOI: 10.1021/acs.jpca.0c01295] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
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Avobenzone (AB) is
a widely used UVA filter known to undergo irreversible
photodegradation. Here, we investigate the detailed pathways by which
AB photodegrades by applying UV laser-interfaced mass spectrometry
to protonated AB ions. Gas-phase infrared multiple-photon dissociation
(IRMPD) spectra obtained with the free electron laser for infrared
experiments, FELIX, (600–1800 cm–1) are also
presented to confirm the geometric structures. The UV gas-phase absorption
spectrum (2.5–5 eV) of protonated AB contains bands that correspond
to selective excitation of either the enol or diketo forms, allowing
us to probe the resulting, tautomer-dependent photochemistry. Numerous
photofragments (i.e., photodegradants) are directly identified for
the first time, with m/z 135 and
161 dominating, and m/z 146 and
177 also appearing prominently. Analysis of the production spectra
of these photofragments reveals that that strong enol to keto photoisomerism
is occurring, and that protonation significantly disrupts the stability
of the enol (UVA active) tautomer. Close comparison of fragment ion
yields with the TD-DFT-calculated absorption spectra give detailed
information on the location and identity of the dissociative excited
state surfaces, and thus provide new insight into the photodegradation
pathways of avobenzone, and photoisomerization of the wider class
of β-diketone containing molecules.
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Affiliation(s)
- Jacob A Berenbeim
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, U.K
| | - Natalie G K Wong
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, U.K
| | - Martin C R Cockett
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, U.K
| | - Giel Berden
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, Nijmegen, 6500 HC, The Netherlands
| | - Jos Oomens
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, Nijmegen, 6500 HC, The Netherlands
| | - Anouk M Rijs
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, Nijmegen, 6500 HC, The Netherlands
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17
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Ohshimo K, Miyazaki S, Hattori K, Misaizu F. Long-distance proton transfer induced by a single ammonia molecule: ion mobility mass spectrometry of protonated benzocaine reacted with NH3. Phys Chem Chem Phys 2020; 22:8164-8170. [DOI: 10.1039/c9cp06923b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A long-distance proton transfer via the vehicle mechanism in the absence of a hydrogen-bonded solvent-bridge in molecules.
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Affiliation(s)
- Keijiro Ohshimo
- Department of Chemistry, Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Shun Miyazaki
- Department of Chemistry, Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Keigo Hattori
- Department of Chemistry, Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
| | - Fuminori Misaizu
- Department of Chemistry, Graduate School of Science
- Tohoku University
- Sendai 980-8578
- Japan
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18
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Direct Observation of Photochemical Free Radical Production from the Sunscreen 2‐Phenylbenzimidazole‐5‐Sulfonic Acid via Laser‐Interfaced Mass Spectrometry. CHEMPHOTOCHEM 2019. [DOI: 10.1002/cptc.201900149] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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19
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Marlton SJP, McKinnon BI, Ucur B, Maccarone AT, Donald WA, Blanksby SJ, Trevitt AJ. Selecting and identifying gas-phase protonation isomers of nicotineH+ using combined laser, ion mobility and mass spectrometry techniques. Faraday Discuss 2019; 217:453-475. [DOI: 10.1039/c8fd00212f] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protonation isomers of gas-phase nicotineH+ are separated and assigned using a combination of FAIMS and UV photodissociation action spectroscopy.
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Affiliation(s)
| | | | - Boris Ucur
- School of Chemistry
- University of Wollongong
- Wollongong
- Australia
| | | | | | - Stephen J. Blanksby
- Central Analytical Research Facility
- Institute for Future Environments
- Queensland University of Technology
- Brisbane
- Australia
| | - Adam J. Trevitt
- School of Chemistry
- University of Wollongong
- Wollongong
- Australia
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20
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Wong NGK, Berenbeim JA, Hawkridge M, Matthews E, Dessent CEH. Mapping the intrinsic absorption properties and photodegradation pathways of the protonated and deprotonated forms of the sunscreen oxybenzone. Phys Chem Chem Phys 2019; 21:14311-14321. [PMID: 30680382 DOI: 10.1039/c8cp06794e] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sunscreens provide vital protection against the photodamaging effects of UV radiation, however, many fundamental questions remain about the detailed mechanisms by which they dissipate UV energy. One such issue is the extent to which the pH environment of an organic sunscreen molecule alters its effectiveness, both in terms of ability to absorb UV radiation, and also its potential to photodegrade. Here, we use gas-phase laser photodissociation spectroscopy for the first time to measure the intrinsic UVA-UVC absorption spectra and associated photodegradation products of protonated and deprotonated oxybenzone, away from the complications of bulk mixtures. Our results reveal that protonation state has a dramatic effect on the absorption and photodissociation properties of this sunscreen. While the UV absorption profile of oxybenzone is only modestly affected by protonation across the range from 400-216 nm, deprotonated oxybenzone displays a significantly modified absorption spectrum, with very low photoabsorption between 370-330 nm. Protonated oxybenzone primarily photofragments by rupture of the bonds on either side of the central carbonyl group, producing cationic fragments with m/z 151 and 105. Additional lower mass photofragments (e.g. m/z 95 and 77) are also observed. The production spectra for the photofragments from protonated oxybenzone fall into two distinct categories, which we discuss in the context of different excited state decay pathways. For deprotonated oxybenzone, the major photofragments observed are m/z 211 and 212, which are associated with the ejection of methane and the methyl free radical from the parent ion, respectively. Implications for the suitability of oxybenzone in its protonated and deprotonated forms as an optimum sunscreen molecule are discussed.
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Affiliation(s)
- Natalie G K Wong
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
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21
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Matthews E, Dessent CEH. Observation of Near-Threshold Resonances in the Flavin Chromophore Anions Alloxazine and Lumichrome. J Phys Chem Lett 2018; 9:6124-6130. [PMID: 30277786 DOI: 10.1021/acs.jpclett.8b02529] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Lumichrome (LC) is the chromophore of the flavin family of photoactive biomolecules, where key biochemical activity involves interplay between redox and photophysical events. Questions remain about the relationship between the redox status of the ground and excited states and demand an improved understanding of the intrinsic photochemistry. Using anion photodissociation spectroscopy, we have measured the intrinsic electronic spectroscopy (564-220 nm) and accompanying photodegradation pathways of the deprotonated anionic form of LC. Experiments were also performed on alloxazine (AL), which is equivalent to LC minus two methyl groups. We observe a resonance state close to 3.8 eV for both anions for the first time, which we tentatively assign to dipole-bound excited states. For AL this state is sufficiently long-lived to facilitate dissociative electron attachment. Our results suggest that the presence of methyl group rotors at key positions along the molecular dipole may reduce the lifetime of the resonance state and hence provide a structural barrier to valence electron capture, and ensuing molecular dissociation.
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Affiliation(s)
- Edward Matthews
- Department of Chemistry , University of York , Heslington, York YO10 5DD , U.K
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22
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Matthews E, Cercola R, Dessent CEH. Protomer-Dependent Electronic Spectroscopy and Photochemistry of the Model Flavin Chromophore Alloxazine. Molecules 2018; 23:molecules23082036. [PMID: 30110962 PMCID: PMC6222404 DOI: 10.3390/molecules23082036] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 08/10/2018] [Accepted: 08/11/2018] [Indexed: 12/16/2022] Open
Abstract
Flavin chromophores play key roles in a wide range of photoactive proteins, but key questions exist in relation to their fundamental spectroscopic and photochemical properties. In this work, we report the first gas-phase spectroscopy study of protonated alloxazine (AL∙H⁺), a model flavin chromophore. Laser photodissociation is employed across a wide range (2.34⁻5.64 eV) to obtain the electronic spectrum and characterize the photofragmentation pathways. By comparison to TDDFT quantum chemical calculations, the spectrum is assigned to two AL∙H⁺ protomers; an N5 (dominant) and O4 (minor) form. The protomers have distinctly different spectral profiles in the region above 4.8 eV due to the presence of a strong electronic transition for the O4 protomer corresponding to an electron-density shift from the benzene to uracil moiety. AL∙H⁺ photoexcitation leads to fragmentation via loss of HCN and HNCO (along with small molecules such as CO₂ and H₂O), but the photofragmentation patterns differ dramatically from those observed upon collision excitation of the ground electronic state. This reveals that fragmentation is occurring during the excited state lifetime. Finally, our results show that the N5 protomer is associated primarily with HNCO loss while the O4 protomer is associated with HCN loss, indicating that the ring-opening dynamics are dependent on the location of protonation in the ground-state molecule.
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Affiliation(s)
- Edward Matthews
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
| | - Rosaria Cercola
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
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23
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Matthews E, Cercola R, Mensa-Bonsu G, Neumark DM, Dessent CEH. Photoexcitation of iodide ion-pyrimidine clusters above the electron detachment threshold: Intracluster electron transfer versus nucleobase-centred excitations. J Chem Phys 2018; 148:084304. [PMID: 29495768 DOI: 10.1063/1.5018168] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Laser photodissociation spectroscopy of the I-·thymine (I-·T) and I-·cytosine (I-·C) nucleobase clusters has been conducted for the first time across the regions above the electron detachment thresholds to explore the excited states and photodissociation channels. Although photodepletion is strong, only weak ionic photofragment signals are observed, indicating that the clusters decay predominantly by electron detachment. The photodepletion spectra of the I-·T and I-·C clusters display a prominent dipole-bound excited state (I) in the vicinity of the vertical detachment energy (∼4.0 eV). Like the previously studied I-·uracil (I-·U) cluster [W. L. Li et al., J. Chem. Phys. 145, 044319 (2016)], the I-·T cluster also displays a second excited state (II) centred at 4.8 eV, which we similarly assign to a π-π* nucleobase-localized transition. However, no distinct higher-energy absorption bands are evident in the spectra of the I-·C. Time-dependent density functional theory (TDDFT) calculations are presented, showing that while each of the I-·T and I-·U clusters displays a single dominant π-π* nucleobase-localized transition, the corresponding π-π* nucleobase transitions for I-·C are split across three separate weaker electronic excitations. I- and deprotonated nucleobase anion photofragments are observed upon photoexcitation of both I-·U and I-·T, with the action spectra showing bands (at 4.0 and 4.8 eV) for both the I- and deprotonated nucleobase anion production. The photofragmentation behaviour of the I-·C cluster is distinctive as its I- photofragment displays a relatively flat profile above the expected vertical detachment energy. We discuss the observed photofragmentation profiles of the I-·pyrimidine clusters, in the context of the previous time-resolved measurements, and conclude that the observed photoexcitations are primarily consistent with intracluster electron transfer dominating in the near-threshold region, while nucleobase-centred excitations dominate close to 4.8 eV. TDDFT calculations suggest that charge-transfer transitions [Iodide n (5p6) → Uracil σ*] may contribute to the cluster absorption profile across the scanned spectral region, and the possible role of these states is also discussed.
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Affiliation(s)
- Edward Matthews
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Rosaria Cercola
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Golda Mensa-Bonsu
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
| | - Daniel M Neumark
- Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Caroline E H Dessent
- Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom
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24
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Pracht P, Bauer CA, Grimme S. Automated and efficient quantum chemical determination and energetic ranking of molecular protonation sites. J Comput Chem 2017; 38:2618-2631. [DOI: 10.1002/jcc.24922] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 07/27/2017] [Accepted: 08/01/2017] [Indexed: 12/20/2022]
Affiliation(s)
- Philipp Pracht
- Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4; 53115 Bonn Germany
| | - Christoph Alexander Bauer
- Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4; 53115 Bonn Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4; 53115 Bonn Germany
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25
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Bull JN, Coughlan NJA, Bieske EJ. Protomer-Specific Photochemistry Investigated Using Ion Mobility Mass Spectrometry. J Phys Chem A 2017; 121:6021-6027. [DOI: 10.1021/acs.jpca.7b05800] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- James N. Bull
- School of Chemistry, University of Melbourne, Parkville, VIC 3010, Australia
| | | | - Evan J. Bieske
- School of Chemistry, University of Melbourne, Parkville, VIC 3010, Australia
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26
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Cercola R, Matthews E, Dessent CEH. Photoexcitation of Adenosine 5'-Triphosphate Anions in Vacuo: Probing the Influence of Charge State on the UV Photophysics of Adenine. J Phys Chem B 2017; 121:5553-5561. [PMID: 28521097 DOI: 10.1021/acs.jpcb.7b03435] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the first UV laser photodissociation spectra (4.0-5.8 eV) of gas-phase deprotonated adenosine 5'-triphosphate, diphosphate and monophosphate anions. The photodepletion spectra of these anions display strong absorption bands across the region of 4.6-5.2 eV, consistent with excitation of a primarily adenine-centered π-π* transition. The spectra appear insensitive to the charge of the species (i.e., the spectrum of [ATP-2H]2- closely resembles that of [ATP-H]-), while the spectral profile is affected to a greater extent by the variation of the molecular structure, i.e. the [AMP-H]- and [ADP-H]- photodepletion spectra display similar profiles while the [ATP-H]- spectrum is distinctive. The photodepletion cross-section also decreases for the ATP anions compared to both the AMP and ADP anions, reflecting a high intrinsic photostability of ATP versus both AMP and ADP. A range of photofragments are produced across the 4.0-5.8 eV spectral range for all of the ATP analogues studied. These fragments are primarily associated with fragmentation on the ground-state electronic surface, indicative of a statistical decay process where ultrafast decay is followed by ergodic dissociation. However, while the photofragments observed following photoexcitation of the monoanionic species, [AMP-H]- to [ADP-H]- to [ATP-H]- are entirely consistent with statistical decay, an additional group of photofragments are observed for the dianionic species, [ADP-2H]2- and [ATP-2H]2-, that we associate with electron detachment, and subsequent fragmentation of the resulting electron-detached photofragment. TDDFT calculations are presented to support the interpretation of the experimental data, and confirm that the electronic structure of the adenine moiety is relatively unperturbed by varying the overall charge.
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Affiliation(s)
- Rosaria Cercola
- Department of Chemistry, University of York , Heslington, York, YO10 5DD, U.K
| | - Edward Matthews
- Department of Chemistry, University of York , Heslington, York, YO10 5DD, U.K
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27
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Abstract
The 37th British Mass Spectrometry Society (BMSS) annual meeting took place over a brilliantly sunny 3 days by the sea in the historic Eastbourne Winter Gardens on the south coast of England. It was held between 13 and 15 September 2016. Two-hundred attendees enjoyed a conference covering all aspects of MS with speakers drawn from across Europe and North America. The BMSS is particularly proud of the encouragement it offers students and early career scientists, both financially in the form of travel grants and also in terms of opportunities to present at an international level in a supportive atmosphere. Further encouragement to newcomers to the field is offered in the form of the Barber Prize for best oral presentation and the Bordoli Prize for the best poster. This year's winners were Patrick Knight (University of Leeds), the Bordoli Prize for the poster 'Characterising the Interaction of Ataxin-3 and the Poly-Glutamine Aggregation Inhibitor QBP1'; Lisa Deininger (Sheffield Hallam University), the Barber Prize for 'Out Damned Spot! Bottom Up Proteomics for the Analysis of Bloodied Fingermarks'. In addition, the Delegates Choice for best poster went to Hannah Britt (Durham University) for 'Monitoring Reactions of Small Molecules with Cell Membranes by Liquid Chromatography-Mass Spectrometry'. For services to the MS community, Professor Gareth Brenton (Swansea University) was awarded the BMSS Medal; Professor Alison Ashcroft (Leeds University) and Anna Upton (former BMSS administrator) were given lifetime membership of the BMSS.
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28
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Matthews E, Dessent CEH. Experiment and theory confirm that UV laser photodissociation spectroscopy can distinguish protomers formed via electrospray. Phys Chem Chem Phys 2017. [DOI: 10.1039/c7cp02817b] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Low-resolution UV spectroscopy within a laser-interfaced commercial mass spectrometer can be used to identify electrosprayed protomers of para-aminobenzoic acid (PABA).
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