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Ieritano C, Featherstone J, Haack A, Guna M, Campbell JL, Hopkins WS. How Hot Are Your Ions in Differential Mobility Spectrometry? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:582-593. [PMID: 31967812 DOI: 10.1021/jasms.9b00043] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ions can experience significant field-induced heating in a differential mobility cell. To investigate this phenomenon, the fragmentation of several para-substituted benzylpyridinium "thermometer" ions (R = OMe, Me, F, Cl, H, CN) was monitored in a commercial differential mobility spectrometer (DMS). The internal energy of each benzylpyridinium derivative was characterized by monitoring the degree of fragmentation to obtain an effective temperature, Teff, which corresponds to a temperature consistent with treating the observed fragmentation ratio using a unimolecular dissociation rate weighted by a Boltzmann distribution at a temperature T. It was found that ions are sufficiently thermalized after initial activation from the ESI process to the temperature of the bath gas, Tbath. Once a critical field strength was surpassed, significant fragmentation of the benzylpyridinium ions was detected. At the maximum bath gas temperature (450 K) and separation voltage (SV; 4400 V) for our instrument, Teff for the benzylpyridinium derivatives ranged from 664 ± 9 K (p-OMe) to 759 ± 17 K (p-H). The extent of activation at a given SV depends on the ion's mass, degrees of freedom, (NDoF), and collision frequency as represented by the ion's collision cross section. Plots of Teff vs the product of ion mass and NDoF and the inverse of collision cross section produce strong linear relationships. This provides an attractive avenue to estimate ion temperatures at a given SV using only intrinsic properties. Moreover, experimentally determined Teff correlate with theoretically predicted Teff using with a self-consistent method based on two-temperature theory. The various instrumental and external parameters that influence Teff are additionally discussed.
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Affiliation(s)
- Christian Ieritano
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Joshua Featherstone
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Alexander Haack
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Strasse 20, Wuppertal 42119, Germany
| | - Mircea Guna
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4 V8, Canada
| | - J Larry Campbell
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4 V8, Canada
| | - W Scott Hopkins
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
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Tu A, Muddiman DC. Internal Energy Deposition in Infrared Matrix-Assisted Laser Desorption Electrospray Ionization With and Without the Use of Ice as a Matrix. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:2380-2391. [PMID: 31502226 PMCID: PMC6937789 DOI: 10.1007/s13361-019-02323-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/13/2019] [Accepted: 08/14/2019] [Indexed: 05/08/2023]
Abstract
The internal energy deposited into analytes during the ionization process largely influences the extent of fragmentation, thus the appearance of the resulting mass spectrum. The internal energy distributions of a series of para-substituted benzyl pyridinium cations in liquid and solid-state generated by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) were measured using the survival yield method, of which results were subsequently compared with conventional electrospray ionization (ESI). The comparable mean internal energy values (e.g., 1.8-1.9 eV at a collision energy of 15 eV) and peak widths obtained with IR-MALDESI and ESI support that IR-MALDESI are essentially a soft ionization technique where analytes do not gain considerable internal energy during the laser-induced desorption process and/or lose energy during uptake into charged electrospray droplets. An unusual fragment ion, protonated pyridine, was only found for solid IR-MALDESI at relatively high collision energies, which is presumably resulted from direct ionization of the pre-charged analytes in form of salts. Analysis of tissue with an ice layer consistently yielded ion populations with higher internal energy than its counterpart without an ice layer, likely due to a substantially enhanced number of IR absorbers with ice. Further measurements with holo-myoglobin show that IR-MALDESI-MS retains the noncovalently bound heme-protein complexes under both native-like and denaturing conditions, while complete loss of the heme group occurred in denaturing ESI-MS, showing that the softness of IR-MALDESI is equivalent or superior to ESI for biomolecules.
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Affiliation(s)
- Anqi Tu
- FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, NC, 27695, USA
| | - David C Muddiman
- FTMS Laboratory for Human Health Research, Department of Chemistry, North Carolina State University, Raleigh, NC, 27695, USA.
- Molecular Education, Technology and Research Innovation Center (METRIC), North Carolina State University, Raleigh, NC, 27695, USA.
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Archer JJ, Karki S, Shi F, Sistani H, Levis RJ. Quantification of Protein-Ligand Interactions by Laser Electrospray Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:1484-1492. [PMID: 29654537 DOI: 10.1007/s13361-018-1935-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 03/01/2018] [Accepted: 03/02/2018] [Indexed: 06/08/2023]
Abstract
Laser electrospray mass spectrometry (LEMS) measurement of the dissociation constant (Kd) for hen egg white lysozyme (HEWL) and N,N',N″-triacetylchitotriose (NAG3) revealed an apparent Kd value of 313.2 ± 25.9 μM for the ligand titration method. Similar measurements for N,N',N″,N″'-tetraacetylchitotetraose (NAG4) revealed an apparent Kd of 249.3 ± 13.6 μM. An electrospray ionization mass spectrometry (ESI-MS) experiment determined a Kd value of 9.8 ± 0.6 μM. In a second LEMS approach, a calibrated measurement was used to determine a Kd value of 6.8 ± 1.5 μM for NAG3. The capture efficiency of LEMS was measured to be 3.6 ± 1.8% and is defined as the fraction of LEMS sample detected after merging with the ESI plume. When the dilution is factored into the ligand titration measurement, the adjusted Kd value was 11.3 μM for NAG3 and 9.0 μM for NAG4. The calibration method for measuring Kd developed in this study can be applied to solutions containing unknown analyte concentrations. Graphical Abstract.
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Affiliation(s)
- Jieutonne J Archer
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Santosh Karki
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Fengjian Shi
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Habiballah Sistani
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Robert J Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA.
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Karki S, Sistani H, Archer JJ, Shi F, Levis RJ. Isolating Protein Charge State Reduction in Electrospray Droplets Using Femtosecond Laser Vaporization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:470-478. [PMID: 28063091 DOI: 10.1007/s13361-016-1576-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 12/08/2016] [Indexed: 06/06/2023]
Abstract
Charge state distributions are measured using mass spectrometry for both native and denatured cytochrome c and myoglobin after laser vaporization from the solution state into an electrospray (ES) plume consisting of a series of solution additives differing in gas-phase basicity. The charge distribution depends on both the pH of the protein solution prior to laser vaporization and the gas-phase basicity of the solution additive employed in the ES solvent. Cytochrome c (myoglobin) prepared in solutions with pH of 7.0, 2.6, and 2.3 resulted in the average charge state distribution (Zavg) of 7.0 ± 0.1 (8.2 ± 0.1), 9.7 ± 0.2 (14.5 ± 0.3), and 11.6 ± 0.3 (16.4 ± 0.1), respectively, in ammonium formate ES solvent. The charge distribution shifted from higher charge states to lower charge states when the ES solvent contained amines additives with higher gas-phase basicity. In the case of triethyl ammonium formate, Zavg of cytochrome c (myoglobin) prepared in solutions with pH of 7.0, 2.6, and 2.3 decreased to 4.9 (5.7), 7.4 ± 0.2 (9.6 ± 0.3), and 7.9 ± 0.3 (9.8 ± 0.2), respectively. The detection of a charge state distribution corresponding to folded protein after laser vaporized, acid-denatured protein interacts with the ES solvent containing ammonium formate, ammonium acetate, triethyl ammonium formate, and triethyl ammonium acetate suggests that at least a part of protein population folds within the electrospray droplet on a millisecond timescale. Graphical Abstract ᅟ.
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Affiliation(s)
- Santosh Karki
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Habiballah Sistani
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Jieutonne J Archer
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Fengjian Shi
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA
| | - Robert J Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA.
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Hassan I, Pavlov J, Errabelli R, Attygalle AB. Oxidative Ionization Under Certain Negative-Ion Mass Spectrometric Conditions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:270-277. [PMID: 27822704 DOI: 10.1007/s13361-016-1527-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 10/09/2016] [Accepted: 10/10/2016] [Indexed: 06/06/2023]
Abstract
1,4-Hydroquinone and several other phenolic compounds generate (M - 2) -• radical-anions, rather than deprotonated molecules, under certain negative-ion mass spectrometric conditions. In fact, spectra generated under helium-plasma ionization (HePI) conditions from 1,4-hydroquinone and 1,4-benzoquinone (by electron capture) were practically indistinguishable. Because this process involves a net loss of H• and H+, it can be termed oxidative ionization. The superoxide radical-anion (O2-•), known to be present in many atmospheric-pressure plasma ion sources operated in the negative mode, plays a critical role in the oxidative ionization process. The presence of a small peak at m/z 142 in the spectrum of 1,4-hydroquinone, but not in that of 1,4-benzoquinone, indicated that the initial step in the oxidative ionization process is the formation of an O2-• adduct. On the other hand, under bona fide electrospray ionization (ESI) conditions, 1,4-hydroquinone generates predominantly an (M - 1) - ion. It is known that at sufficiently high capillary voltages, corona discharges begin to occur even in an ESI source. At lower ESI capillary voltages, deprotonation predominates; as the capillary voltage is raised, the abundance of O2-• present in the plasma increases, and the source in turn increasingly behaves as a composite ESI/APCI source. While maintaining post-ionization ion activation to a minimum (to prevent fragmentation), and monitoring the relative intensities of the m/z 109 (due to deprotonation) and 108 (oxidative ionization) peaks recorded from 1,4-hydroquinone, a semiquantitative estimation of the APCI contribution to the overall ion-generation process can be obtained. Graphical Abstract ᅟ.
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Affiliation(s)
- Isra Hassan
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Julius Pavlov
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Ramu Errabelli
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Athula B Attygalle
- Center for Mass Spectrometry, Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
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Shi F, Flanigan PM, Archer JJ, Levis RJ. Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:542-551. [PMID: 26667178 DOI: 10.1007/s13361-015-1302-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 10/22/2015] [Accepted: 10/27/2015] [Indexed: 06/05/2023]
Abstract
Direct analysis of plant and animal tissue samples by laser electrospray mass spectrometry (LEMS) was investigated using low-energy, femtosecond duration laser vaporization at wavelengths of 800 and 1042 nm followed by nanospray postionization. Low-energy (<50 μJ), fiber-based 1042 nm LEMS (F-LEMS) allowed interrogation of the molecular species in fresh flower petal and leaf samples using 435 fs, 10 Hz bursts of 20 pulses from a Ytterbium-doped fiber laser and revealed comparable results to high energy (75-1120 μJ), 45 fs, 800 nm Ti:Sapphire-based LEMS (Ti:Sapphire-LEMS) measurements. Anthocyanins, sugars, and other metabolites were successfully detected and revealed the anticipated metabolite profile for the petal and leaf samples. Phospholipids, especially phosphatidylcholine, were identified from a fresh mouse brain section sample using Ti:Sapphire-LEMS without the application of matrix. These lipid features were suppressed in both the fiber-based and Ti:Sapphire-based LEMS measurements when the brain sample was prepared using the optimal cutting temperature compounds that are commonly used in animal tissue cryosections.
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Affiliation(s)
- Fengjian Shi
- Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
- Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
| | - Paul M Flanigan
- Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
- Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
- Signature Science, LLC., 2819 Fire Rd, Egg Harbor Township, NJ, 08234, USA
| | - Jieutonne J Archer
- Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
- Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA
| | - Robert J Levis
- Department of Chemistry, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA.
- Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA, 19122, USA.
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Shi F, Archer JJ, Levis RJ. Nonresonant, femtosecond laser vaporization and electrospray post-ionization mass spectrometry as a tool for biological tissue imaging. Methods 2016; 104:79-85. [PMID: 26931651 DOI: 10.1016/j.ymeth.2016.02.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 02/19/2016] [Accepted: 02/24/2016] [Indexed: 12/30/2022] Open
Abstract
An ambient mass spectrometry imaging (MSI) source is demonstrated with both high spatial and mass resolution that enables measurement of the compositional heterogeneity within a biological tissue sample. The source is based on nonresonant, femtosecond laser electrospray mass spectrometry (LEMS) coupled to a quadrupole time-of-flight (QTOF) mass analyzer. No matrix deposition and minimal sample preparation is necessary for the source. The laser, translation stage, and mass spectrometer are synchronized and controlled using a customized user interface. Single or multiple laser shots may be applied to each pixel. A scanning rate of 2.0s per pixel is achieved. Measurement of a patterned ink film indicates the potential of LEMS for ambient imaging with a lateral resolution of ∼60μm. Metabolites including sugar, anthocyanins and other small metabolites were successfully mapped from plant samples without oversampling using a spot size of 60×70μm(2). Molecular identification of the detected analytes from the tissue was enabled by accurate mass measurement in conjunction with tandem mass spectrometry. Statistical analysis, non-negative matrix factorization and principle component analysis, were applied to the imaging data to extract regions with distinct and/or correlated spectral profiles.
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Affiliation(s)
- Fengjian Shi
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA 19122, United States
| | - Jieutonne J Archer
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA 19122, United States
| | - Robert J Levis
- Department of Chemistry and Center for Advanced Photonics Research, Temple University, 1901 N. 13th St., Philadelphia, PA 19122, United States.
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Shi F, Flanigan PM, Archer JJ, Levis RJ. Direct analysis of intact biological macromolecules by low-energy, fiber-based femtosecond laser vaporization at 1042 nm wavelength with nanospray postionization mass spectrometry. Anal Chem 2015; 87:3187-94. [PMID: 25688836 DOI: 10.1021/ac502563c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A fiber-based laser with a pulse duration of 435 fs and a wavelength of 1042 nm was used to vaporize biological macromolecules intact from the condensed phase into the gas phase for nanospray postionization and mass analysis. Laser vaporization of dried standard protein samples from a glass substrate by 10 Hz bursts of 20 pulses having 10 μs pulse separation and <50 μJ pulse energy resulted in signal comparable to a metal substrate. The protein signal observed from an aqueous droplet on a glass substrate was negligible compared to either a droplet on metal or a thin film on glass. The mass spectra generated from dried and aqueous protein samples by the low-energy, fiber laser were similar to the results from high-energy (500 μJ), 45-fs, 800-nm Ti:sapphire-based femtosecond laser electrospray mass spectrometry (LEMS) experiments, suggesting that the fiber-based femtosecond laser desorption mechanism involves a nonresonant, multiphoton process, rather than thermal- or photoacoustic-induced desorption. Direct analysis of whole blood performed without any pretreatment resulted in features corresponding to hemoglobin subunit-heme complex ions. The observation of intact molecular ions with low charge states from protein, and the tentatively assigned hemoglobin α subunit-heme complex from blood suggests that fiber-based femtosecond laser vaporization is a "soft" desorption source at a laser intensity of 2.39 × 10(12) W/cm(2). The low-energy, turnkey fiber laser demonstrates the potential of a more robust and affordable laser for femtosecond laser vaporization to deliver biological macromolecules into the gas phase for mass analysis.
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Affiliation(s)
- Fengjian Shi
- †Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.,‡Center for Advanced Photonics Research, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Paul M Flanigan
- †Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.,‡Center for Advanced Photonics Research, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Jieutonne J Archer
- †Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.,‡Center for Advanced Photonics Research, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
| | - Robert J Levis
- †Department of Chemistry, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States.,‡Center for Advanced Photonics Research, Temple University, 1901 North 13th Street, Philadelphia, Pennsylvania 19122, United States
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