1
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Fu L, Eakins GS, Carlsen MS, McLuckey SA. Single-Frequency Ion Parking in a Digital 3D Quadrupole Ion Trap. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2024; 503:117282. [PMID: 39006163 PMCID: PMC11238766 DOI: 10.1016/j.ijms.2024.117282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
Single-frequency ion parking, a useful technique in electrospray mass spectrometry (ESI-MS), involves gas-phase charge-reduction ion/ion reactions in an electrodynamic ion trap in conjunction with the application of a supplementary oscillatory voltage to selectively inhibit the reaction rate of an ion of interest. The ion parking process provides a means for limiting the extent of charge reduction in a controlled fashion and allows for ions distributed over a range of charge states to be concentrated into fewer charge states (a single charge state under optimal conditions). As charge reduction inherently leads to an increase in the mass-to-charge (m/z) ratio of the ions, it is important that the means for storing and analyzing ions be able to accommodate ions of high m/z ratios. The so-called 'digital ion trap' (DIT), which uses a digital waveform as the trapping RF, has been demonstrated to be well-suited for the analysis of high m/z ions by taking advantage of its ability to manipulate the waveform frequency. In this study, the feasibility of ion parking in a 3D quadrupole ion trap operated as a DIT using a slow-amplitude single-frequency sine-wave for selective inhibition of an ion/ion reaction is demonstrated. A recently described model that describes ion parking has been adjusted for the DIT case and is used to interpret experimental data for proteins ranging in mass from 8600 Da to 467,000 Da.
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Affiliation(s)
- Liangxuan Fu
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | - Gregory S Eakins
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | - Mark S Carlsen
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | - Scott A McLuckey
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
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2
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Mikawy NN, Rojas Ramírez C, DeFiglia SA, Szot CW, Le J, Lantz C, Wei B, Zenaidee MA, Blakney GT, Nesvizhskii AI, Loo JA, Ruotolo BT, Shabanowitz J, Anderson LC, Håkansson K. Are Internal Fragments Observable in Electron Based Top-Down Mass Spectrometry? Mol Cell Proteomics 2024:100814. [PMID: 39029587 DOI: 10.1016/j.mcpro.2024.100814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Revised: 06/26/2024] [Accepted: 07/12/2024] [Indexed: 07/21/2024] Open
Abstract
Protein tandem mass spectrometry (MS/MS) often generates sequence-informative fragments from backbone bond cleavages near the termini. This lack of fragmentation in the protein interior is particularly apparent in native top-down MS. Improved sequence coverage, critical for reliable annotation of posttranslational modifications (PTMs) and sequence variants, may be obtained from internal fragments generated by multiple backbone cleavage events. However, internal fragment assignments can be error prone due to isomeric/isobaric fragments from different parts of a protein sequence. Also, internal fragment generation propensity depends on the chosen MS/MS activation strategy. Here, we examine internal fragment formation in electron capture dissociation (ECD) and electron transfer dissociation (ETD) following native and denaturing MS, as well as liquid chromatography (LC)/MS of several proteins. Experiments were undertaken on multiple instruments, including Q-ToF, Orbitrap, and high-field FT-ICR across four laboratories. ECD was performed at both ultrahigh vacuum and at similar pressure to ETD conditions. Two complementary software packages were used for data analysis. When feasible, ETD-higher-energy collision dissociation (ETD-HCD) MS3 was performed to validate/refute potential internal fragment assignments, including differentiating MS3 fragmentation behavior of radical vs. even-electron primary fragments. We show that, under typical operating conditions, internal fragments cannot be confidently assigned in ECD, nor ETD. On the other hand, such fragments, along with some b-type terminal fragments (not typically observed in ECD/ETD spectra) appear at atypical ECD operating conditions, suggesting they originate from a separate ion-electron activation process. Furthermore, atypical fragment ion types, e.g., x ions, are observed at such conditions as well as upon EThcD, presumably due to vibrational activation of radical z-type ions.
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Affiliation(s)
- Neven N Mikawy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States; Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Ain-Shams University, Cairo, Egypt
| | - Carolina Rojas Ramírez
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States; Department of Pathology, University of Michigan, Ann Arbor, MI 48109-5602, United States
| | - Steven A DeFiglia
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States
| | - Carson W Szot
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States
| | - Jessie Le
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, United States
| | - Carter Lantz
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, United States
| | - Benqian Wei
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, United States
| | - Muhammad A Zenaidee
- Australian Proteome Analysis Facility, Macquarie University, Sydney, NSW, 2109, Australia
| | - Greg T Blakney
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States
| | - Alexey I Nesvizhskii
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109-5602, United States; Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109-2218, United States
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States
| | - Jeffrey Shabanowitz
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, United States
| | - Lissa C Anderson
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States
| | - Kristina Håkansson
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, United States.
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3
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Zhu Y, Liu Z, Liu J, Zhao H, Feng R, Shu K, Wang F, Chang C. Panda-UV Unlocks Deeper Protein Characterization with Internal Fragments in Ultraviolet Photodissociation Mass Spectrometry. Anal Chem 2024; 96:8474-8483. [PMID: 38739687 PMCID: PMC11140674 DOI: 10.1021/acs.analchem.4c00253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 05/06/2024] [Accepted: 05/06/2024] [Indexed: 05/16/2024]
Abstract
Ultraviolet photodissociation (UVPD) mass spectrometry unlocks insights into the protein structure and sequence through fragmentation patterns. While N- and C-terminal fragments are traditionally relied upon, this work highlights the critical role of internal fragments in achieving near-complete sequencing of protein. Previous limitations of internal fragment utilization, owing to their abundance and potential for random matching, are addressed here with the development of Panda-UV, a novel software tool combining spectral calibration, and Pearson correlation coefficient scoring for confident fragment assignment. Panda-UV showcases its power through comprehensive benchmarks on three model proteins. The inclusion of internal fragments boosts identified fragment numbers by 26% and enhances average protein sequence coverage to a remarkable 93% for intact proteins, unlocking the hidden region of the largest protein carbonic anhydrase II in model proteins. Notably, an average of 65% of internal fragments can be identified in multiple replicates, demonstrating the high confidence of the fragments Panda-UV provided. Finally, the sequence coverages of mAb subunits can be increased up to 86% and the complementary determining regions (CDRs) are nearly completely sequenced in a single experiment. The source codes of Panda-UV are available at https://github.com/PHOENIXcenter/Panda-UV.
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Affiliation(s)
- Yinlong Zhu
- Chongqing
Key Laboratory on Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
- State
Key Laboratory of Medical Proteomics, Beijing
Proteome Research Center, National Center for Protein Sciences (Beijing),
Beijing Institute of Lifeomics, Beijing 102206, China
- CAS
Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian
Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
| | - Zheyi Liu
- CAS
Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian
Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of
Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, China
| | - Jialiang Liu
- CAS
Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian
Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of
Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- School of
Pharmacy, China Medical University, Shenyang 110122, China
| | - Heng Zhao
- CAS
Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian
Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of
Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Rui Feng
- State
Key Laboratory of Medical Proteomics, Beijing
Proteome Research Center, National Center for Protein Sciences (Beijing),
Beijing Institute of Lifeomics, Beijing 102206, China
| | - Kunxian Shu
- Chongqing
Key Laboratory on Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
| | - Fangjun Wang
- CAS
Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian
Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
- State
Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of
Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- University
of Chinese Academy of Sciences, Beijing 100049, China
| | - Cheng Chang
- State
Key Laboratory of Medical Proteomics, Beijing
Proteome Research Center, National Center for Protein Sciences (Beijing),
Beijing Institute of Lifeomics, Beijing 102206, China
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4
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Peters-Clarke TM, Coon JJ, Riley NM. Instrumentation at the Leading Edge of Proteomics. Anal Chem 2024; 96:7976-8010. [PMID: 38738990 DOI: 10.1021/acs.analchem.3c04497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Affiliation(s)
- Trenton M Peters-Clarke
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
- Department of Biomolecular Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
- Department of Biomolecular Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States
- Morgridge Institute for Research, Madison, Wisconsin 53715, United States
| | - Nicholas M Riley
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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5
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Pizzala NJ, Bhanot JS, Carrick IJ, Dziekonski ET, McLuckey SA. Ion parking in native mass spectrometry. Analyst 2024; 149:2966-2977. [PMID: 38600834 PMCID: PMC11089522 DOI: 10.1039/d4an00242c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 04/05/2024] [Indexed: 04/12/2024]
Abstract
A forced, damped harmonic oscillator model for gas-phase ion parking using single-frequency resonance excitation is described and applied to high-mass ions of relevance to native mass spectrometry. Experimental data are provided to illustrate key findings revealed by the modelling. These include: (i) ion secular frequency spacings between adjacent charge states of a given protein are essentially constant and decrease with the mass of the protein (ii) the mechanism for ion parking of high mass ions is the separation of the ion clouds of the oppositely-charged ions with much less influence from an increase in the relative ion velocity due to resonance excitation, (iii) the size of the parked ion cloud ultimately limits ion parking at high m/z ratio, and (iv) the extent of ion parking of off-target ions is highly sensitive to the bath gas pressure in the ion trap. The model is applied to ions of 17 kDa, 467 kDa, and 2 MDa while experimental data are also provided for ions of horse skeletal muscle myoglobin (≈17 kDa) and β-galactosidase (≈467 kDa). The model predicts and data show that it is possible to effect ion parking on a 17 kDa protein to the 1+ charge state under trapping conditions that are readily accessible with commercially available ion traps. It is also possible to park β-galactosidase efficiently to a roughly equivalent m/z ratio (i.e., the 26+ charge state) under the same trapping conditions. However, as charge states decrease, analyte ion cloud sizes become too large to allow for efficient ion trapping. The model allows for a semi-quantitative prediction of ion trapping performance as a function of ion trapping, resonance excitation, and pressure conditions.
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Affiliation(s)
- Nicolas J Pizzala
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Jay S Bhanot
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Ian J Carrick
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Eric T Dziekonski
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Scott A McLuckey
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
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6
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Drown BS, Gupta R, McGee JP, Hollas MAR, Hergenrother PJ, Kafader JO, Kelleher NL. Precise Readout of MEK1 Proteoforms upon MAPK Pathway Modulation by Individual Ion Mass Spectrometry. Anal Chem 2024; 96:4455-4462. [PMID: 38458998 PMCID: PMC11008683 DOI: 10.1021/acs.analchem.3c04758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2024]
Abstract
The functions of proteins bearing multiple post-translational modifications (PTMs) are modulated by their modification patterns, yet precise characterization of them is difficult. MEK1 (also known as MAP2K1) is one such example that acts as a gatekeeper of the mitogen-activating protein kinase (MAPK) pathway and propagates signals via phosphorylation by upstream kinases. In principle, top-down mass spectrometry can precisely characterize whole MEK1 proteoforms, but fragmentation methods that would enable the site-specific characterization of labile modifications on 43 kDa protein ions result in overly dense tandem mass spectra. By using the charge-detection method called individual ion mass spectrometry, we demonstrate how complex mixtures of phosphoproteoforms and their fragment ions can be reproducibly handled to provide a "bird's eye" view of signaling activity through mapping proteoform landscapes in a pathway. Using this approach, the overall stoichiometry and distribution of 0-4 phosphorylations on MEK1 was determined in a cellular model of drug-resistant metastatic melanoma. This approach can be generalized to other multiply modified proteoforms, for which PTM combinations are key to their function and drug action.
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Affiliation(s)
- Bryon S Drown
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Raveena Gupta
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - John P McGee
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Michael A R Hollas
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Paul J Hergenrother
- Department of Chemistry, Carl R. Woese Institute for Genomic Biology, Cancer Center at Illinois, University of Illinois at Urbana─Champaign, Urbana, Illinois 61801, United States
| | - Jared O Kafader
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Neil L Kelleher
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
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7
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Dunham SD, Brodbelt JS. Enhancing Top-Down Analysis of Proteins by Combining Ultraviolet Photodissociation (UVPD), Proton-Transfer Charge Reduction (PTCR), and Gas-Phase Fractionation to Alleviate the Impact of Nondissociated Precursor Ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:255-265. [PMID: 38150423 DOI: 10.1021/jasms.3c00351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Recent advances in top-down mass spectrometry strategies continue to improve the analysis of intact proteins. 193 nm ultraviolet photodissociation (UVPD) is one method well-suited for top-down analysis. UVPD is often performed using relatively low photon flux in order to limit multiple-generation dissociation of fragment ions and maximize sequence coverage. Consequently, a large portion of the precursor ion survives the UVPD process, dominates the spectrum, and may impede identification of fragment ions. Here, we explore the isolation of subpopulations of fragment ions lower and higher than the precursor ion after UVPD as a means to eliminate the impact of the surviving precursor ion on the detection of low abundance fragment ions. This gas-phase fractionation method improved sequence coverage harvested from fragment ions found in the m/z regions lower and higher than the precursor by an average factor of 1.3 and 2.3, respectively. Combining this gas-phase fractionation method with proton transfer charge reduction (PTCR) further increased the sequence coverage obtained from these m/z regions by another factor of 1.3 and 1.4, respectively. Implementing a post-UVPD fractionation + PTCR strategy with six fractionation events resulted in a sequence coverage of 75% for enolase, the highest reported for 193 nm UVPD.
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Affiliation(s)
- Sean D Dunham
- Department of Chemistry, University of Texas, Austin, Texas 787812, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas, Austin, Texas 787812, United States
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8
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Liu FC, Ridgeway ME, Wootton CA, Theisen A, Panczyk EM, Meier F, Park MA, Bleiholder C. Top-Down Protein Analysis by Tandem-Trapped Ion Mobility Spectrometry/Mass Spectrometry (Tandem-TIMS/MS) Coupled with Ultraviolet Photodissociation (UVPD) and Parallel Accumulation/Serial Fragmentation (PASEF) MS/MS Analysis. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2232-2246. [PMID: 37638640 PMCID: PMC11162218 DOI: 10.1021/jasms.3c00187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
"Top-down" proteomics analyzes intact proteins and identifies proteoforms by their intact mass as well as the observed fragmentation pattern in tandem mass spectrometry (MS/MS) experiments. Recently, hybrid ion mobility spectrometry-mass spectrometry (IM/MS) methods have gained traction for top-down experiments, either by allowing top-down analysis of individual isomers or alternatively by improving signal/noise and dynamic range for fragment ion assignment. We recently described the construction of a tandem-trapped ion mobility spectrometer/mass spectrometer (tandem-TIMS/MS) coupled with an ultraviolet (UV) laser and demonstrated a proof-of-principle for top-down analysis by UV photodissociation (UVPD) at 2-3 mbar. The present work builds on this with an exploration of a top-down method that couples tandem-TIMS/MS with UVPD and parallel-accumulation serial fragmentation (PASEF) MS/MS analysis. We first survey types and structures of UVPD-specific fragment ions generated in the 2-3 mbar pressure regime of our instrument. Notably, we observe UVPD-induced fragment ions with multiple conformations that differ from those produced in the absence of UV irradiation. Subsequently, we discuss how MS/MS spectra of top-down fragment ions lend themselves ideally for probability-based scoring methods developed in the bottom-up proteomics field and how the ability to record automated PASEF-MS/MS spectra resolves ambiguities in the assignment of top-down fragment ions. Finally, we describe the coupling of tandem-TIMS/MS workflows with UVPD and PASEF-MS/MS analysis for native top-down protein analysis.
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Affiliation(s)
- Fanny C. Liu
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32304, USA
| | | | | | | | | | - Florian Meier
- Functional Proteomics, Jena University Hospital, 07747 Jena, Germany
| | | | - Christian Bleiholder
- Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32304, USA
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9
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Walker JN, Lam R, Brodbelt JS. Enhanced Characterization of Histones Using 193 nm Ultraviolet Photodissociation and Proton Transfer Charge Reduction. Anal Chem 2023; 95:5985-5993. [PMID: 36989418 DOI: 10.1021/acs.analchem.2c05765] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Top-down characterization of histones, proteins that are critical participants in an array of DNA-dependent processes, offers the potential to examine the relationship between histone structure and mechanisms of genetic regulation. Mapping patterns of post-translational modifications (PTMs) of histones requires extensive backbone cleavages to bracket the sites of mass shifts corresponding to specific PTMs. Ultraviolet photodissociation (UVPD) causes substantial fragmentation of proteins, which is well-suited for PTM localization, but the resulting spectra are congested with fragment ions that may have overlapping isotopic distributions that confound deconvolution. Gas-phase proton transfer charge reduction (PTCR) decreases the charge states of highly charged ions, thus alleviating this congestion and facilitating the identification of additional sequence-determining and PTM-localizing fragment ions. By integrating UVPD with PTCR for histone proteoform analyses, sequence coverages up to 91% were achieved for calf thymus histone H4 containing acetylation marks at the N-terminus and Lys12 as well as a dimethylation at Arg3. UVPD-PTCR exhibited large gains in characterization for other histones, such as histone H2A, increasing the sequence coverage from 59 to 77% for monoacetylated H2A.
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Affiliation(s)
- Jada N Walker
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Raymond Lam
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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10
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Lin Y, Agarwal AM, Anderson LC, Marshall AG. Discovery of a biomarker for β-Thalassemia by HPLC-MS and improvement from Proton Transfer Reaction - Parallel Ion Parking. J Mass Spectrom Adv Clin Lab 2023; 28:20-26. [PMID: 36814695 PMCID: PMC9939715 DOI: 10.1016/j.jmsacl.2023.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 01/20/2023] [Accepted: 01/20/2023] [Indexed: 02/05/2023] Open
Abstract
β-thalassemia is a quantitative hemoglobin (Hb) disorder resulting in reduced production of Hb A and increased levels of Hb A2. Diagnosis of β-thalassemia can be problematic when combined with other structural Hb variants, so that the separation approaches in routine clinical centers are not sufficiently decisive to obtain accurate results. Here, we separate the intact Hb subunits by high-performance liquid chromatography, followed by top-down tandem mass spectrometry of intact subunits to distinguish Hb variants. Proton transfer reaction-parallel ion parking (PTR-PIP), in which a radical anion removes protons from multiply charged precursor ions and produces charge-reduced ions spanning a limited m/z range, was used to increase the signal-to-noise ratio of the subunits of interest. We demonstrate that the δ/β ratio can act as a biomarker to identify β-thalassemia in normal electrospray ionization MS1 and PTR-PIP MS1. The application of PTR-PIP significantly increases the sensitivity and specificity of the HPLC-MS method to identify δ/β ratio as a thalassemia biomarker.
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Key Words
- ACN, Acetonitrile
- AUC, Areas under the curve
- CID, Collision-induced dissociation
- ESI, Electrospray ionization
- ETD, Electron-transfer dissociation
- FA, Formic acid
- FN, False-negative
- FP, False-positive
- FT-ICR
- FT-ICR, MS Fourier transform ion cyclotron resonance mass spectrometer
- FTMS
- Fourier transform ion cyclotron resonance
- Hb A, Normal adult Hb
- Hb, Hemoglobin
- HbA1d, Hb β with glutathione
- IFCC, International Federation of Clinical Chemistry and Laboratory Medicine
- IQR, Interquartile range
- J, Youden Index
- MCW, Methanol/chloroform/water
- MS, Mass spectrometry
- PTM, Post-translational modification
- PTR-PIP, Proton transfer reaction-parallel ion parking
- ROC, Receiver operating characteristic
- S/N, Signal-to-noise ratios
- Se(c), Sensitivity, the probability of a true positive)
- Sp(c), Specificity, the probability of a true negative)
- TIC, Total ion chromatogram
- TN, True negative
- TP, True positive
- Top-down
- XIC, Extracted ion chromatograms
- m/z, Mass-to-charge ratios
- δ/β ratio
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Affiliation(s)
- Yuan Lin
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States
| | - Archana M. Agarwal
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT 84132, United States,ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT 84108, United States
| | - Lissa C. Anderson
- Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States,Corresponding authors at: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States (A.G. Marshall).
| | - Alan G. Marshall
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States,Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, United States,Corresponding authors at: Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32308, United States (A.G. Marshall).
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11
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Dunham SD, Wei B, Lantz C, Loo JA, Brodbelt JS. Impact of Internal Fragments on Top-Down Analysis of Intact Proteins by 193 nm UVPD. J Proteome Res 2023; 22:170-181. [PMID: 36503236 DOI: 10.1021/acs.jproteome.2c00583] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
193 nm ultraviolet photodissociation (UVPD) allows high sequence coverage to be obtained for intact proteins using terminal fragments alone. However, internal fragments, those that contain neither N- nor C- terminus, are typically ignored, neglecting their potential to bolster characterization of intact proteins. Here, we explore internal fragments generated by 193 nm UVPD for proteins ranging in size from 17-47 kDa and using the ClipsMS algorithm to facilitate searches for internal fragments. Internal fragments were only retained if identified in multiple replicates in order to reduce spurious assignments and to explore the reproducibility of internal fragments generated by UVPD. Inclusion of internal fragment improved sequence coverage by an average of 18% and 32% for UVPD and HCD, respectively, across all proteins and charge states studied. However, only an average of 18% of UVPD internal fragments were identified in two out of three replicates relative to the average number identified across all replicates for all proteins studied. Conversely, for HCD, an average of 63% of internal fragments were retained across replicates. These trends reflect an increased risk of false-positive identifications and a need for caution when considering internal fragments for UVPD. Additionally, proton-transfer charge reduction (PTCR) reactions were performed following UVPD or HCD to assess the impact on internal fragment identifications, allowing up to 20% more fragment ions to be retained across multiple replicates. At this time, it is difficult to recommend the inclusion of the internal fragment when searching UVPD spectra without further work to develop strategies for reducing the possibilities of false-positive identifications. All mass spectra are available in the public repository jPOST with the accession number JPST001885.
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Affiliation(s)
- Sean D Dunham
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Benqian Wei
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Carter Lantz
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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12
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Brodbelt JS. Deciphering combinatorial post-translational modifications by top-down mass spectrometry. Curr Opin Chem Biol 2022; 70:102180. [PMID: 35779351 PMCID: PMC9489649 DOI: 10.1016/j.cbpa.2022.102180] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 05/30/2022] [Accepted: 05/31/2022] [Indexed: 12/15/2022]
Abstract
Post-translational modifications (PTMs) create vast structural and functional diversity of proteins, ultimately modulating protein function and degradation, influencing cellular signaling, and regulating transcription. The combinatorial patterns of PTMs increase the heterogeneity of proteins and further mediates their interactions. Advances in mass spectrometry-based proteomics have resulted in identification of thousands of proteins and allowed characterization of numerous types and sites of PTMs. Examination of intact proteins, termed the top-down approach, offers the potential to map protein sequences and localize multiple PTMs on each protein, providing the most comprehensive cataloging of proteoforms. This review describes some of the dividends of using mass spectrometry to analyze intact proteins and showcases innovative strategies that have enhanced the promise of top-down proteomics for exploring the impact of combinatorial PTMs in unsurpassed detail.
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Affiliation(s)
- Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, TX 78712, USA.
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13
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Bhanot JS, Fabijanczuk KC, Abdillahi AM, Chao HC, Pizzala NJ, Londry FA, Dziekonski ET, Hager JW, McLuckey SA. Adaptation and Operation of a Quadrupole/Time-of-Flight Tandem Mass Spectrometer for High Mass Ion/Ion Reaction Studies. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2022; 478:116874. [PMID: 37032994 PMCID: PMC10081487 DOI: 10.1016/j.ijms.2022.116874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
A commercial quadrupole/time-of-flight tandem mass spectrometer has been modified and evaluated for its performance in conducting ion/ion reaction studies involving high mass (>100 kDa) ions. Modifications include enabling the application of dipolar AC waveforms to opposing rods in three quadrupole arrays in the ion path. This modification allows for resonance excitation of ions to effect ion activation, selective ion isolation, and ion parking. The other set of opposing rods in each array is enabled for the application of dipolar DC voltages for the purpose of broad-band (non-selective) ion heating. The plates between each quadrupole array are enabled for the application of either DC or AC (or both) voltages. The use of AC voltages allows for the simultaneous storage of ions of opposite polarity, thereby enabling mutual storage ion/ion reactions. Ions derived from nano-electrospray ionization of GroEL and β-galactosidase under native conditions were used to evaluate limits of instrument performance, in terms of m/z range, ion isolation, and ion storage. After adjustment of the pulser frequency, ions as high in m/z as 400,000 were detected. Significant losses in efficiency were noted above m/z 250,000 that is likely due to roll-over in the ion detector efficiency and possibly also due to limitations in ion transfer efficiency from the collision quadrupole to the pulser region of the mass analyzer. No measurable decrease in the apparent mass resolving power was noted upon charge state reduction of the model ions. Resonance ejection techniques that employ the dipolar AC capabilities of the quadrupoles allow for ion isolation at m/z values much greater than the RF/DC limitation of Q1 of m/z = 2100. For example, at the highest low-mass cutoff achievable in the collision quadrupole (m/z = 500), it is possible to isolate ions of m/z as high as 62,000. This is limited by the lowest dipolar AC frequency (5 kHz) that can be applied. A simple model is included to provide for an estimate of the ion cloud radius based on ion m/z, ion z, and ion trap operating conditions. The model predicts that singly charged ions of 1 MDa and thermal energy can be contained in the ion trap at the maximum low-mass cutoff, although such an ion would not be detected efficiently. Doubly charged GroEL ions were observed experimentally. Collectively, the performance characteristics at high m/z, the functionality provided by the standard instrument capabilities, the modifications described above, and highly flexible instrument control software provide for a highly versatile platform for the study of high mass ion/ion reactions.
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Affiliation(s)
- Jay S. Bhanot
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | | | | | - Hsi-Chun Chao
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | - Nicolas J. Pizzala
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
| | | | | | | | - Scott A. McLuckey
- Department of Chemistry, Purdue University, West Lafayette, IN, USA 47907-2084
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14
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Fornelli L, Toby TK. Characterization of large intact protein ions by mass spectrometry: What directions should we follow? BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140758. [PMID: 35077914 DOI: 10.1016/j.bbapap.2022.140758] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 01/07/2022] [Accepted: 01/11/2022] [Indexed: 11/16/2022]
Abstract
Theoretically, the gas-phase interrogation of whole proteoforms via mass spectrometry, known as top-down proteomics, bypasses the protein inference problem that afflicts peptide-centric proteomic approaches. Despite this obvious advantage, the application of top-down proteomics remains rare, mainly due to limited throughput and difficulty of analyzing proteins >30 kDa. Here we will discuss some of the problems encountered during the characterization of large proteoforms, and guided by a combination of theoretical background and experimental evidence we will describe some innovative data acquisition strategies and novel mass spectrometry technologies that can at least partially overcome such limitations.
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Affiliation(s)
- Luca Fornelli
- University of Oklahoma, Department of Biology, 730 Van Vleet oval, Norman, OK 73109, United States of America; University of Oklahoma, Department Chemistry and Biochemistry, 101 Stephenson Parkway, Norman, OK 73109, United States of America.
| | - Timothy K Toby
- DiscernDx, 2478 Embarcadero Way, Palo Alto, CA 94303, United States of America
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15
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Shaw JB, Cooper-Shepherd DA, Hewitt D, Wildgoose JL, Beckman JS, Langridge JI, Voinov VG. Enhanced Top-Down Protein Characterization with Electron Capture Dissociation and Cyclic Ion Mobility Spectrometry. Anal Chem 2022; 94:3888-3896. [PMID: 35188751 PMCID: PMC8908312 DOI: 10.1021/acs.analchem.1c04870] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Tandem mass spectrometry of denatured, multiply charged high mass protein precursor ions yield extremely dense spectra with hundreds of broad and overlapping product ion isotopic distributions of differing charge states that yield an elevated baseline of unresolved "noise" centered about the precursor ion. Development of mass analyzers and signal processing methods to increase mass resolving power and manipulation of precursor and product ion charge through solution additives or ion-ion reactions have been thoroughly explored as solutions to spectral congestion. Here, we demonstrate the utility of electron capture dissociation (ECD) coupled with high-resolution cyclic ion mobility spectrometry (cIMS) to greatly increase top-down protein characterization capabilities. Congestion of protein ECD spectra was reduced using cIMS of the ECD product ions and "mobility fractions", that is, extracted mass spectra for segments of the 2D mobiligram (m/z versus drift time). For small proteins, such as ubiquitin (8.6 kDa), where mass resolving power was not the limiting factor for characterization, pre-IMS ECD and mobility fractions did not significantly increase protein sequence coverage, but an increase in the number of identified product ions was observed. However, a dramatic increase in performance, measured by protein sequence coverage, was observed for larger and more highly charged species, such as the +35 charge state of carbonic anhydrase (29 kDa). Pre-IMS ECD combined with mobility fractions yielded a 135% increase in the number of annotated isotope clusters and a 75% increase in unique product ions compared to processing without using the IMS dimension. These results yielded 89% sequence coverage for carbonic anhydrase.
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Affiliation(s)
- Jared B. Shaw
- e-MSion
Inc., 2121 NE Jack London Street, Corvallis, Oregon 97330, United States, (J.S.)
| | | | - Darren Hewitt
- Waters
Corporation, Wilmslow, Cheshire SK9 4AX, U.K.
| | | | - Joseph S. Beckman
- e-MSion
Inc., 2121 NE Jack London Street, Corvallis, Oregon 97330, United States,Linus
Pauling Institute and the Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, United States
| | | | - Valery G. Voinov
- e-MSion
Inc., 2121 NE Jack London Street, Corvallis, Oregon 97330, United States
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