1
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Kline JT, Huang J, Lieu LB, Srzentić K, Bergen D, Mullen C, McAlister GC, Durbin KR, Melani RD, Fornelli L. Top-down mass spectrometry analysis of capsid proteins of recombinant adeno-associated virus using multiple ion activations and proton transfer charge reduction. Proteomics 2024:e2400223. [PMID: 39233542 DOI: 10.1002/pmic.202400223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2024] [Revised: 08/03/2024] [Accepted: 08/26/2024] [Indexed: 09/06/2024]
Abstract
Adeno-associated viruses (AAVs) are common vectors for emerging gene therapies due to their lack of pathogenicity in humans. Here, we present our investigation of the viral proteins (i.e., VP1, VP2, and VP3) of the capsid of AAVs via top-down mass spectrometry (MS). These proteins, ranging from 59 to 81 kDa, were chromatographically separated using hydrophilic interaction liquid chromatography and characterized in the gas-phase by high-resolution Orbitrap Fourier transform MS. Complementary ion dissociation methods were utilized to improve the overall sequence coverage. By reducing the overlap of product ion signals via proton transfer charge reduction on the Orbitrap Ascend BioPharma Tribrid mass spectrometer, the sequence coverage of each VP was significantly increased, reaching up to ∼40% in the case of VP3. These results showcase the improvements in the sequencing of proteins >30 kDa that can be achieved by manipulating product ions via gas-phase reactions to obtain easy-to-interpret fragmentation mass spectra.
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Affiliation(s)
| | | | | | | | - David Bergen
- Thermo Fisher Scientific, San Jose, California, USA
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2
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Shaw JB, Harvey SR, Du C, Xu Z, Edgington RM, Olmedillas E, Saphire EO, Wysocki VH. Protein Complex Heterogeneity and Topology Revealed by Electron Capture Charge Reduction and Surface Induced Dissociation. ACS CENTRAL SCIENCE 2024; 10:1537-1547. [PMID: 39220701 PMCID: PMC11363329 DOI: 10.1021/acscentsci.4c00461] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Revised: 06/26/2024] [Accepted: 07/01/2024] [Indexed: 09/04/2024]
Abstract
We illustrate the utility of native mass spectrometry (nMS) combined with a fast, tunable gas-phase charge reduction, electron capture charge reduction (ECCR), for the characterization of protein complex topology and glycoprotein heterogeneity. ECCR efficiently reduces the charge states of tetradecameric GroEL, illustrating Orbitrap m/z measurements to greater than 100,000 m/z. For pentameric C-reactive protein and tetradecameric GroEL, our novel device combining ECCR with surface induced dissociation (SID) reduces the charge states and yields more topologically informative fragmentation. This is the first demonstration that ECCR yields more native-like SID fragmentation. ECCR also significantly improved mass and glycan heterogeneity measurements of heavily glycosylated SARS-CoV-2 spike protein trimer and thyroglobulin dimer. Protein glycosylation is important for structural and functional properties and plays essential roles in many biological processes. The immense heterogeneity in glycosylation sites and glycan structure poses significant analytical challenges that hinder a mechanistic understanding of the biological role of glycosylation. Without ECCR, average mass determination of glycoprotein complexes is available only through charge detection mass spectrometry or mass photometry. With narrow m/z selection windows followed by ECCR, multiple glycoform m/z values are apparent, providing quick global glycoform profiling and providing a future path for glycan localization on individual intact glycoforms.
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Affiliation(s)
- Jared B. Shaw
- Department
of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Sophie R. Harvey
- Native
Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, Ohio 43210, United States
| | - Chen Du
- Native
Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, Ohio 43210, United States
- Department
of Chemistry and Biochemistry, Ohio State
University, Columbus, Ohio 43210, United
States
| | - Zhixin Xu
- Native
Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, Ohio 43210, United States
- Department
of Chemistry and Biochemistry, Ohio State
University, Columbus, Ohio 43210, United
States
| | - Regina M. Edgington
- Department
of Chemistry and Biochemistry, Ohio State
University, Columbus, Ohio 43210, United
States
| | - Eduardo Olmedillas
- Center
for Vaccine Innovation, La Jolla Institute
for Immunology, La Jolla, California 92037, United States
| | - Erica Ollmann Saphire
- Center
for Vaccine Innovation, La Jolla Institute
for Immunology, La Jolla, California 92037, United States
- Department
of Medicine, University of California San
Diego, La Jolla, California 92037, United States
| | - Vicki H. Wysocki
- Native
Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, Ohio 43210, United States
- Department
of Chemistry and Biochemistry, Ohio State
University, Columbus, Ohio 43210, United
States
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3
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Shaw JB, Harvey SR, Du C, Xu Z, Edgington RM, Olmedillas E, Saphire EO, Wysocki VH. Protein complex heterogeneity and topology revealed by electron capture charge reduction and surface induced dissociation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.07.583498. [PMID: 38496594 PMCID: PMC10942452 DOI: 10.1101/2024.03.07.583498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
We illustrate the utility of native mass spectrometry (nMS) combined with a fast, tunable gas-phase charge reduction, electron capture charge reduction (ECCR), for the characterization of protein complex topology and glycoprotein heterogeneity. ECCR efficiently reduces the charge states of tetradecameric GroEL, illustrating Orbitrap m/z measurements to greater than 100,000 m/z. For pentameric C-reactive protein and tetradecameric GroEL, our novel device combining ECCR with surface induced dissociation (SID) reduces the charge states and yields more topologically informative fragmentation. This is the first demonstration that ECCR yields more native-like SID fragmentation. ECCR also significantly improved mass and glycan heterogeneity measurements of heavily glycosylated SARS-CoV-2 spike protein trimer and thyroglobulin dimer. Protein glycosylation is important for structural and functional properties and plays essential roles in many biological processes. The immense heterogeneity in glycosylation sites and glycan structure poses significant analytical challenges that hinder a mechanistic understanding of the biological role of glycosylation. Without ECCR, average mass determination of glycoprotein complexes is available only through charge detection mass spectrometry or mass photometry. With narrow m/z selection windows followed by ECCR, multiple glycoform m/z values are apparent, providing quick global glycoform profiling and providing a future path for glycan localization on individual intact glycoforms.
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Affiliation(s)
- Jared B Shaw
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588
| | - Sophie R Harvey
- Native Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, OH 43210
| | - Chen Du
- Native Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, OH 43210
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210
| | - Zhixin Xu
- Native Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, OH 43210
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210
| | - Regina M Edgington
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210
| | - Eduardo Olmedillas
- Center for Vaccine Innovation, La Jolla Institute for Immunology, La Jolla, CA 92037
| | - Erica Ollmann Saphire
- Center for Vaccine Innovation, La Jolla Institute for Immunology, La Jolla, CA 92037
- Department of Medicine, University of California San Diego, La Jolla, CA 92037
| | - Vicki H Wysocki
- Native Mass Spectrometry Guided Structural Biology Center, Ohio State University, Columbus, OH 43210
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210
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4
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Graham KA, Grisolia VJ, Borotto NB. Mobility-Assisted Pseudo-MS 3 Sequencing of Protein Ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024. [PMID: 38920020 DOI: 10.1021/jasms.4c00148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
The sequencing of intact proteins within a mass spectrometer has many benefits but is frequently limited by the fact that tandem mass spectrometry (MS/MS) techniques often generate poor sequence coverages when applied to protein ions. To overcome this limitation, exotic MS/MS techniques that rely on lasers and radical chemistry have been developed. These techniques generate high sequence coverages, but they require specialized instrumentation, create products through multiple dissociation mechanisms, and often require long acquisition times. Recently, we demonstrated that protein ions can be dissociated in a trapped ion mobility spectrometry (TIMS) device prior to mobility separation in a commercial timsTOF. All generated product ions were distributed throughout the mobility dimension, and this separation enabled deconvolution of complex tandem mass spectra and could enable facile pseudo-MS3 interrogation of generated product ions with the downstream quadrupole and collision cell. A second activation step improves sequence coverage because the most labile bonds have been depleted during the first dissociation and subsequent dissociation events are more evenly distributed throughout the product ion backbone. In this work, we explore the potential of this mobility-assisted pseudo-MS3 (MAP) method on a commercial timsTOF and timsTOF Pro 2. We demonstrate that while MAP only generates 92% of the sequence coverage of the most effective MS/MS technique, it accomplished this feat in 1.5 min and could be facilely integrated with liquid chromatographic separations.
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Affiliation(s)
- Katherine A Graham
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, Nevada 89557, United States
| | - Vincent J Grisolia
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, Nevada 89557, United States
| | - Nicholas B Borotto
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, Nevada 89557, United States
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5
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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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6
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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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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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Gass DT, Cordes MS, Alberti SN, Kim HJ, Gallagher ES. Evidence of H/D Exchange within Metal-Adducted Carbohydrates after Ion/Ion-Dissociation Reactions. J Am Chem Soc 2023; 145:23972-23985. [PMID: 37874934 DOI: 10.1021/jacs.3c05793] [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: 10/26/2023]
Abstract
Tandem mass spectrometry (MS/MS) using fragmentation has become one of the most effective methods for gaining sequence and structural information on biomolecules. Ion/ion reactions are competitive reactions, where either proton transfer (PT) or electron transfer (ET) can occur from interactions between multiply charged cations and singly charged anions. Utilizing ion/ion reactions with fluoranthene has offered a unique method of fragment formation for the structural elucidation of biomolecules. Fluoranthene is considered an ideal anion reagent because it selectively causes electron-transfer dissociation (ETD) and minimizes PT when interacting with peptides. However, limited investigations have sought to understand how fluoranthene─the primary, commercially available anion reagent─interacts with other biomolecules. Here, we apply deuterium labeling to investigate ion/ion reaction mechanisms between fluoranthene and divalent, metal-adducted carbohydrates (Ca2+, Mg2+, Co2+, and Ni2+). Deuterium labeling of carbohydrates allowed us to observe evidence of hydrogen/deuterium exchange (HDX) occurring after ion/ion dissociation reactions. The extent of deuterium loss is dependent on several factors, including the physical properties of the metal ion and the fragment structure. Based on the deuterium labeling data, we have proposed ETD, PTD, and intermolecular PT─also described as HDX─mechanisms. This research provides a fundamental perspective of ion/ion and ion/molecule reaction mechanisms and illustrates properties that impact ion/ion and ion/molecule reactions for carbohydrates. Together, this could improve the capability to distinguish complex and heterogeneous biomolecules, such as carbohydrates.
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Affiliation(s)
- Darren T Gass
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Michael S Cordes
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Sebastian N Alberti
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - H Jamie Kim
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
| | - Elyssia S Gallagher
- Department of Chemistry and Biochemistry, Baylor University, Waco, Texas 76798, United States
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9
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Kline JT, Melani RD, Fornelli L. Mass spectrometry characterization of antibodies at the intact and subunit levels: from targeted to large-scale analysis. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2023; 492:117117. [PMID: 38855125 PMCID: PMC11160972 DOI: 10.1016/j.ijms.2023.117117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Antibodies are one of the most formidable molecular weapons available to our immune system. Their high specificity against a target (antigen) and capability of triggering different immune responses (e.g., complement system activation and antibody-dependent cell-mediated cytotoxicity) make them ideal drugs to fight many different human diseases. Currently, both monoclonal antibodies and more complex molecules based on the antibody scaffold are used as biologics. Naturally, such highly heterogeneous molecules require dedicated analytical methodologies for their accurate characterization. Mass spectrometry (MS) can define the presence and relative abundance of multiple features of antibodies, including critical quality attributes. The combination of small and large variations within a single molecule can only be determined by analyzing intact antibodies or their large (25 to 100 kDa) subunits. Hence, top-down (TD) and middle-down (MD) MS approaches have gained popularity over the last decade. In this Young Scientist Feature we discuss the evolution of TD and MD MS analysis of antibodies, including the new frontiers that go beyond biopharma applications. We will show how this field is now moving from the "quality control" analysis of a known, single antibody to the high-throughput investigation of complex antibody repertoires isolated from clinical samples, where the ultimate goal is represented by the complete gas-phase sequencing of antibody molecules without the need of any a priori knowledge.
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Affiliation(s)
- Jake T. Kline
- Department of Biology, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Rafael D. Melani
- Thermo Fisher Scientific, San Jose, California 95134, United States
| | - Luca Fornelli
- Department of Biology, University of Oklahoma, Norman, Oklahoma 73019, United States
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States
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10
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Bashyal A, Dunham SD, Brodbelt JS. Characterization of Unbranched Ubiquitin Tetramers by Combining Ultraviolet Photodissociation with Proton Transfer Charge Reduction Reactions. Anal Chem 2023; 95:14001-14008. [PMID: 37677053 DOI: 10.1021/acs.analchem.3c02618] [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: 09/09/2023]
Abstract
Polyubiquitination is an important post-translational modification (PTM) that regulates various biological functions. The linkage sites and topologies of polyubiquitination chains are important factors in determining the fate of polyubiquitinated proteins. Characterization of polyubiquitin chains is the first step in understanding the biological functions of protein ubiquitination, but it is challenging owing to the repeating nature of the ubiquitin chains and the difficulty in deciphering linkage positions. Here, we combine ultraviolet photodissociation (UVPD) mass spectrometry and gas-phase proton transfer charge reduction (PTCR) to facilitate the assignment of product ions generated from Lys6-, Lys11-, Lys29-, Lys33-, Lys48-, and Lys63-linked ubiquitin tetramers. UVPD results in extensive fragmentation of intact proteins in a manner that allows the localization of PTMs. However, UVPD mass spectra of large proteins (>30 kDa) are often congested due to the overlapping isotopic distribution of highly charged fragment ions. UVPD + PTCR improved the identification of PTM-containing fragment ions, allowing the localization of linkage sites in all six tetramers analyzed. UVPD + PTCR also increased the sequence coverage obtained from the PTM-containing fragment ions in each of the four chains of each tetramer by 7 to 44% when compared to UVPD alone.
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Affiliation(s)
- Aarti Bashyal
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Sean D Dunham
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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11
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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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12
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Graham KA, Lawlor CF, Borotto NB. Characterizing the top-down sequencing of protein ions prior to mobility separation in a timsTOF. Analyst 2023; 148:1534-1542. [PMID: 36876327 PMCID: PMC10042122 DOI: 10.1039/d2an01682f] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 02/28/2023] [Indexed: 03/07/2023]
Abstract
Mass spectrometry (MS)-based proteomics workflows of intact protein ions have increasingly been utilized to study biological systems. These workflows, however, frequently result in convoluted and difficult to analyze mass spectra. Ion mobility spectrometry (IMS) is a promising tool to overcome these limitations by separating ions by their mass- and size-to-charge ratios. In this work, we further characterize a newly developed method to collisionally dissociate intact protein ions in a trapped ion mobility spectrometry (TIMS) device. Dissociation occurs prior to ion mobility separation and thus, all product ions are distributed throughout the mobility dimension, enabling facile assignment of near isobaric product ions. We demonstrate that collisional activation within a TIMS device is capable of dissociating protein ions up to 66 kDa. We also demonstrate that the ion population size within the TIMS device significantly influences the efficiency of fragmentation. Lastly, we compare CIDtims to the other modes of collisional activation available on the Bruker timsTOF and demonstrate that the mobility resolution in CIDtims enables the annotation of overlapping fragment ions and improves sequence coverage.
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Affiliation(s)
- Katherine A Graham
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA.
| | - Charles F Lawlor
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA.
| | - Nicholas B Borotto
- Department of Chemistry, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA.
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13
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Lanzillotti M, Brodbelt JS. Comparison of Top-Down Protein Fragmentation Induced by 213 and 193 nm UVPD. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:279-285. [PMID: 36594540 DOI: 10.1021/jasms.2c00288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The growing interest in advancing tandem mass spectrometry strategies for top-down proteomics has motivated efforts to optimize ion activation strategies for intact proteins, including the comparison of 193 and 213 nm wavelengths for ultraviolet photodissociation (UVPD). The present study focuses on the performance and outcomes of UVPD for five proteins, ubiquitin, cytochrome C, frataxin, myoglobin, and carbonic anhydrase, with an emphasis on evaluating the similarities and differences in fragmentation promoted by UVPD using 193 nm versus 213 nm photons. Mass spectra were collected as a function of the number of laser pulses, and precursor depletion levels were monitored and controlled to provide consistent energy deposition between 213 and 193 nm UVPD. Fragment ions were confirmed on the basis of their isotopic distributions in m/z space to preserve both charge state and abundance information and were classified on the basis of ion type and frequency. A large portion of the total fragment ion abundance was attributable to preferential cleavages, particularly ones adjacent to proline residues. These cleavages were examined on the basis of the backbone site and abundances, revealing that a and y-2 ions N-terminal to proline residues appeared at disproportionately high abundances in 213 nm UVPD spectra as compared to 193 nm UVPD spectra, highlighting one notable difference in the top-down spectra. We theorize that these fragments are formed more efficiently in 213 nm UVPD than in 193 nm UVPD due to increased absorption of 213 nm photons at the proline amide bond.
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Affiliation(s)
- Michael Lanzillotti
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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14
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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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15
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Zhu J, Lei L, Wu P, Cheng B, Yang XL, Fu J, Wu Z, He F. The intervention effect of mental health knowledge integrated into ideological and political teaching on college students’ employment and entrepreneurship mentality. Front Psychol 2022; 13:1002468. [PMID: 36267069 PMCID: PMC9577364 DOI: 10.3389/fpsyg.2022.1002468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 08/18/2022] [Indexed: 11/18/2022] Open
Abstract
In order to analyze the intervention effect of integrating mental health knowledge into ideological and political teaching on college students’ employment and entrepreneurship mentality, this paper proposes a study to predict the effect of integrated intervention. This research mainly investigates the ideological and psychological conditions of college students from divorced families through questionnaires, compares and analyzes the classification and statistical results of the survey data between groups and within groups, and analyzes the reasons for the ideological and psychological problems of college students. The experimental results show that 30% of college students from divorced families and college students from non-divorced families responded that they do not feel comfortable in places with many people, and the difference between the groups is not significant. Regarding the concept of entrepreneurship, 64.63% of college students from divorced families in urban areas believe that entrepreneurship is a form of learning and should be encouraged. 63.27% of college students from divorced families in rural areas believe that learning should be the first priority and that a business should not be started. 20.41% of college students from divorced families in rural areas and 25.61% of college students from divorced families in urban areas believe that because entrepreneurship provides economic income, it can reduce the burden on families, but the difference is not obvious. In short, this study can provide reference for the ideological and psychological status of college students from divorced families.
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Affiliation(s)
- Jiaming Zhu
- School of Foreign Languages and Literatures, Chongqing University of Education, Chongqing, China
- *Correspondence: Jiaming Zhu,
| | - Lanchuan Lei
- School of Foreign Languages and Literatures, Chongqing University of Education, Chongqing, China
| | - Pengjv Wu
- School of Literature and Communication, Chongqing Three Gorges University, Chongqing, China
| | - Bo Cheng
- School of Foreign Languages and Literatures, Chongqing University of Education, Chongqing, China
| | - Xiu-lan Yang
- School of Basic Medical Sciences, Yangtze University, Jingzhou, Hubei, China
| | - Jing Fu
- School of Mathematics Physics and Big Data, Chongqing University of Science and Technology, Chongqing, China
| | - Zhaoxia Wu
- School of Foreign Languages and Literatures, Chongqing University of Education, Chongqing, China
| | - Fangcheng He
- School of Foreign Languages and Literatures, Chongqing University of Education, Chongqing, China
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16
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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: 25] [Impact Index Per Article: 12.5] [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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17
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Chen Q, Dai R, Yao X, Chaihu L, Tong W, Huang Y, Wang G. Improving Accuracy in Mass Spectrometry-Based Mass Determination of Intact Heterogeneous Protein Utilizing the Universal Benefits of Charge Reduction and Alternative Gas-Phase Reactions. Anal Chem 2022; 94:13869-13878. [PMID: 36170625 DOI: 10.1021/acs.analchem.2c02586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In mass analysis of proteins, mass spectrometry directly measures the mass to charge ratios of ionized proteins and promises higher accuracy than that of indirect approaches measuring other physicochemical properties, provided that the charge states of detected ions are determined. Accurate mass determination of heterogeneously glycosylated proteins is often hindered by unreliable charge determination due to the insufficient resolution of signals from different charge states and inconsistency among mass profiles of ions in individual charge states. Limited charge reduction of a subpopulation of proteoforms using electron transfer/capture reactions (ETnoD/ETnoD) solves this problem by narrowing the mass distribution of examined proteoforms and preserving the mass profile of the precursor charge state in the reduced charge states. However, the limited availability of ETnoD/ETnoD function in commercial instruments limits the application of this approach. Here, utilizing a range of charge-dependent and accuracy-affecting spectral features revealed by a systematic evaluation at levels of both the ensemble and subpopulation of proteoforms based on theoretical models and experiments, we developed a limited charge reduction workflow that enables using collision-induced dissociation and higher energy collisional dissociation, two widely available reactions, as alternatives to ETnoD/ETnoD while providing adequate accuracy. Alternatively, substituting proton transfer charge reduction for ETnoD/ETnoD provides higher accuracy of mass determination. Performing mass selection in a window-sliding manner improves the accuracy and allows profiling of the whole proteoform distribution. The proposed workflow may facilitate the development of universal characterization strategies for more complex and heterogeneous protein systems.
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Affiliation(s)
- Qingrong Chen
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China.,Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Rongrong Dai
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China.,Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Xiaopeng Yao
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China.,Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Lingxiao Chaihu
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China.,Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Wenjun Tong
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
| | - Yanyi Huang
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China.,Biomedical Pioneering Innovation Centre, Peking University, Beijing 100871, China
| | - Guanbo Wang
- Institute for Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China.,Biomedical Pioneering Innovation Centre, Peking University, Beijing 100871, China
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18
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Liu R, Xia S, Li H. Native top-down mass spectrometry for higher-order structural characterization of proteins and complexes. MASS SPECTROMETRY REVIEWS 2022:e21793. [PMID: 35757976 DOI: 10.1002/mas.21793] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Progress in structural biology research has led to a high demand for powerful and yet complementary analytical tools for structural characterization of proteins and protein complexes. This demand has significantly increased interest in native mass spectrometry (nMS), particularly native top-down mass spectrometry (nTDMS) in the past decade. This review highlights recent advances in nTDMS for structural research of biological assemblies, with a particular focus on the extra multi-layers of information enabled by TDMS. We include a short introduction of sample preparation and ionization to nMS, tandem fragmentation techniques as well as mass analyzers and software/analysis pipelines used for nTDMS. We highlight unique structural information offered by nTDMS and examples of its broad range of applications in proteins, protein-ligand interactions (metal, cofactor/drug, DNA/RNA, and protein), therapeutic antibodies and antigen-antibody complexes, membrane proteins, macromolecular machineries (ribosome, nucleosome, proteosome, and viruses), to endogenous protein complexes. The challenges, potential, along with perspectives of nTDMS methods for the analysis of proteins and protein assemblies in recombinant and biological samples are discussed.
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Affiliation(s)
- Ruijie Liu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Shujun Xia
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Huilin Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
- Guangdong Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
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19
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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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20
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Dunham SD, Sanders JD, Holden DD, Brodbelt JS. Improving the Center Section Sequence Coverage of Large Proteins Using Stepped-Fragment Ion Protection Ultraviolet Photodissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:446-456. [PMID: 35119856 DOI: 10.1021/jasms.1c00296] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ultraviolet photodissociation (UVPD) mass spectrometry has gained attention in recent years for its ability to provide high sequence coverage of intact proteins. However, secondary dissociation of fragment ions, in which fragment ions subjected to multiple laser pulses decompose into small products, is a common phenomenon during UVPD that contributes to limited coverage in the midsection of protein sequences. To counter secondary dissociation, a method involving the application of notched waveforms to modulate the trajectories of fragment ions away from the laser beam, termed fragment ion protection (FIP), was previously developed to reduce the probability of secondary dissociation. This, in turn, increased the number of identified large fragment ions. In the present study, FIP was applied to UVPD of large proteins ranging in size from 29 to 55 kDa, enhancing the abundances of large fragment ions. A stepped-FIP strategy was implemented in which UVPD mass spectra were collected using multiple different amplitudes of the FIP waveforms and then the results from the mass spectra were combined. By using stepped-FIP, the number of fragment ions in the midsections of the sequences increased for all proteins. For example, whereas no fragment ions were identified in the middle section of the sequence for glutamate dehydrogenase (55 kDa, 55+ charge state), 10 sequence ions were identified by using UVPD-FIP.
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Affiliation(s)
- Sean D Dunham
- Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - James D Sanders
- Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Dustin D Holden
- Department of Chemistry, University of Texas, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas, Austin, Texas 78712, United States
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21
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Macias LA, Sipe SN, Santos IC, Bashyal A, Mehaffey MR, Brodbelt JS. Influence of Primary Structure on Fragmentation of Native-Like Proteins by Ultraviolet Photodissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2860-2873. [PMID: 34714071 PMCID: PMC8639798 DOI: 10.1021/jasms.1c00269] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Analysis of native-like protein structures in the gas phase via native mass spectrometry and auxiliary techniques has become a powerful tool for structural biology applications. In combination with ultraviolet photodissociation (UVPD), native top-down mass spectrometry informs backbone flexibility, topology, hydrogen bonding networks, and conformational changes in protein structure. Although it is known that the primary structure affects dissociation of peptides and proteins in the gas phase, its effect on the types and locations of backbone cleavages promoted by UVPD and concomitant influence on structural characterization of native-like proteins is not well understood. Here, trends in the fragmentation of native-like proteins were evaluated by tracking the propensity of 10 fragment types (a, a+1, b, c, x, x+1, y, y-1, Y, and z) in relation to primary structure in a native-top down UVPD data set encompassing >9600 fragment ions. Differing fragmentation trends are reported for the production of distinct fragment types, attributed to a combination of both direct dissociation pathways from excited electronic states and those surmised to involve intramolecular vibrational energy redistribution after internal conversion. The latter pathways were systematically evaluated to evince the role of proton mobility in the generation of "CID-like" fragments through UVPD, providing pertinent insight into the characterization of native-like proteins. Fragmentation trends presented here are envisioned to enhance analysis of the protein higher-order structure or augment scoring algorithms in the high-throughput analysis of intact proteins.
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Affiliation(s)
- Luis A Macias
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sarah N Sipe
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Inês C Santos
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Aarti Bashyal
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - M Rachel Mehaffey
- 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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22
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Kline JT, Mullen C, Durbin KR, Oates RN, Huguet R, Syka JEP, Fornelli L. Sequential Ion-Ion Reactions for Enhanced Gas-Phase Sequencing of Large Intact Proteins in a Tribrid Orbitrap Mass Spectrometer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2334-2345. [PMID: 33900069 DOI: 10.1021/jasms.1c00062] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Obtaining extensive sequencing of an intact protein is essential in order to simultaneously determine both the nature and exact localization of chemical and genetic modifications which distinguish different proteoforms arising from the same gene. To effectively achieve such characterization, it is necessary to take advantage of the analytical potential offered by the top-down mass spectrometry approach to protein sequence analysis. However, as a protein increases in size, its gas-phase dissociation produces overlapping, low signal-to-noise fragments. The application of advanced ion dissociation techniques such as electron transfer dissociation (ETD) and ultraviolet photodissociation (UVPD) can improve the sequencing results compared to slow-heating techniques such as collisional dissociation; nonetheless, even ETD- and UVPD-based approaches have thus far fallen short in their capacity to reliably enable extensive sequencing of proteoforms ≥30 kDa. To overcome this issue, we have applied proton transfer charge reduction (PTCR) to limit signal overlap in tandem mass spectra (MS2) produced by ETD (alone or with supplemental ion activation, EThcD). Compared to conventional MS2 experiments, following ETD/EThcD MS2 with PTCR MS3 prior to m/z analysis of deprotonated product ions in the Orbitrap mass analyzer proved beneficial for the identification of additional large protein fragments (≥10 kDa), thus improving the overall sequencing and in particular the coverage of the central portion of all four analyzed proteins spanning from 29 to 56 kDa. Specifically, PTCR-based data acquisition led to 39% sequence coverage for the 56 kDa glutamate dehydrogenase, which was further increased to 44% by combining fragments obtained via HCD followed by PTCR MS3.
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Affiliation(s)
- Jake T Kline
- Department of Biology, University of Oklahoma, 730 Van Vleet Oval, Norman, Oklahoma 73019, United States
| | - Christopher Mullen
- Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | | | - Ryan N Oates
- Department of Chemistry and Biochemistry, University of Oklahoma, 730 Van Vleet Oval, Norman, Oklahoma 73019, United States
| | - Romain Huguet
- Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | - John E P Syka
- Thermo Fisher Scientific, 355 River Oaks Parkway, San Jose, California 95134, United States
| | - Luca Fornelli
- Department of Biology, University of Oklahoma, 730 Van Vleet Oval, Norman, Oklahoma 73019, United States
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23
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Campuzano IDG, Sandoval W. Denaturing and Native Mass Spectrometric Analytics for Biotherapeutic Drug Discovery Research: Historical, Current, and Future Personal Perspectives. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1861-1885. [PMID: 33886297 DOI: 10.1021/jasms.1c00036] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Mass spectrometry (MS) plays a key role throughout all stages of drug development and is now as ubiquitous as other analytical techniques such as surface plasmon resonance, nuclear magnetic resonance, and supercritical fluid chromatography, among others. Herein, we aim to discuss the history of MS, both electrospray and matrix-assisted laser desorption ionization, specifically for the analysis of antibodies, evolving through to denaturing and native-MS analysis of newer biologic moieties such as antibody-drug conjugates, multispecific antibodies, and interfering nucleic acid-based therapies. We discuss challenging therapeutic target characterization such as membrane protein receptors. Importantly, we compare and contrast the MS and hyphenated analytical chromatographic methods used to characterize these therapeutic modalities and targets within biopharmaceutical research and highlight the importance of appropriate MS deconvolution software and its essential contribution to project progression. Finally, we describe emerging applications and MS technologies that are still predominantly within either a development or academic stage of use but are poised to have significant impact on future drug development within the biopharmaceutic industry once matured. The views reflected herein are personal and are not meant to be an exhaustive list of all relevant MS performed within biopharmaceutical research but are what we feel have been historically, are currently, and will be in the future the most impactful for the drug development process.
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MESH Headings
- Antibodies, Monoclonal/analysis
- Automation, Laboratory
- Biopharmaceutics/methods
- Chromatography, Liquid
- Drug Discovery/methods
- Drug Industry/history
- History, 20th Century
- History, 21st Century
- Humans
- Immunoconjugates/analysis
- Immunoconjugates/chemistry
- Protein Denaturation
- Protein Processing, Post-Translational
- Proteins/analysis
- Spectrometry, Mass, Electrospray Ionization/history
- Spectrometry, Mass, Electrospray Ionization/instrumentation
- Spectrometry, Mass, Electrospray Ionization/methods
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/history
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/instrumentation
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods
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Affiliation(s)
- Iain D G Campuzano
- Discovery Attribute Sciences, Amgen Research, 1 Amgen Center Drive, Thousand Oaks, California 92130, United States
| | - Wendy Sandoval
- Department of Microchemistry, Proteomics and Lipidomics, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
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24
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Zenaidee MA, Wei B, Lantz C, Wu HT, Lambeth TR, Diedrich JK, Loo RRO, Julian RR, Loo JA. Internal Fragments Generated from Different Top-Down Mass Spectrometry Fragmentation Methods Extend Protein Sequence Coverage. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1752-1758. [PMID: 34101447 PMCID: PMC9090460 DOI: 10.1021/jasms.1c00113] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Top-down mass spectrometry (TD-MS) of intact proteins results in fragment ions that can be correlated to the protein primary sequence. Fragments generated can either be terminal fragments that contain the N- or C-terminus or internal fragments that contain neither termini. Traditionally in TD-MS experiments, the generation of internal fragments has been avoided because of ambiguity in assigning these fragments. Here, we demonstrate that in TD-MS experiments internal fragments can be formed and assigned in collision-based, electron-based, and photon-based fragmentation methods and are rich with sequence information, allowing for a greater extent of the primary protein sequence to be explained. For the three test proteins cytochrome c, myoglobin, and carbonic anhydrase II, the inclusion of internal fragments in the analysis resulted in approximately 15-20% more sequence coverage, with no less than 85% sequence coverage obtained. Combining terminal fragment and internal fragment assignments results in near complete protein sequence coverage. Hence, by including both terminal and internal fragment assignments in TD-MS analysis, deep protein sequence analysis, allowing for the localization of modification sites more reliably, can be possible.
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Affiliation(s)
- Muhammad A. Zenaidee
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095
| | - Benqian Wei
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095
| | - Carter Lantz
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095
| | - Hoi Ting Wu
- Department of Chemistry, University of California Riverside, Riverside, CA 92521
| | - Tyler R. Lambeth
- Department of Chemistry, University of California Riverside, Riverside, CA 92521
| | - Jolene K. Diedrich
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037
| | - Rachel R. Ogorzalek Loo
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095
| | - Ryan R. Julian
- Department of Chemistry, University of California Riverside, Riverside, CA 92521
| | - Joseph A. Loo
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095
- Department of Biological Chemistry, University of California Los Angeles, Los Angeles, CA 90095
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25
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Weisbrod CR, Anderson LC, Hendrickson CL, Schaffer LV, Shortreed MR, Smith LM, Shabanowitz J, Hunt DF. Advanced Strategies for Proton-Transfer Reactions Coupled with Parallel Ion Parking on a 21 T FT-ICR MS for Intact Protein Analysis. Anal Chem 2021; 93:9119-9128. [PMID: 34165955 DOI: 10.1021/acs.analchem.1c00847] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton-transfer reactions (PTRs) have emerged as a powerful tool for the study of intact proteins. When coupled with m/z-selective kinetic excitation, such as parallel ion parking (PIP), one can exert exquisite control over rates of reaction with a high degree of specificity. This allows one to "concentrate", in the gas phase, nearly all the signals from an intact protein charge state envelope into a single charge state, improving the signal-to-noise ratio (S/N) by 10× or more. While this approach has been previously reported, here we show that implementing these technologies on a 21 T FT-ICR MS provides a tremendous advantage for intact protein analysis. Advanced strategies for performing PTR with PIP were developed to complement this unique instrument, including subjecting all analyte ions entering the mass spectrometer to PTR and PIP. This experiment, which we call "PTR-MS1-PIP", generates a pseudo-MS1 spectrum derived from ions that are exposed to the PTR reagent and PIP waveforms but have not undergone any prior true mass filtering or ion isolation. The result is an extremely rapid and significant improvement in the spectral S/N of intact proteins. This permits the observation of many more proteoforms and reduces ion injection periods for subsequent tandem mass spectrometry characterization. Additionally, the product ion parking waveform has been optimized to enhance the PTR rate without compromise to the parking efficiency. We demonstrate that this process, called "rapid park", can improve reaction rates by 5-10× and explore critical factors discovered to influence this process. Finally, we demonstrate how coupling PTR-MS1 and rapid park provides a 10-fold reduction in ion injection time, improving the rate of tandem MS sequencing.
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Affiliation(s)
- Chad R Weisbrod
- Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
| | - Lissa C Anderson
- Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
| | - Christopher L Hendrickson
- Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr., Tallahassee, Florida 32310, United States
| | - Leah V Schaffer
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Michael R Shortreed
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Lloyd M Smith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Jeffrey Shabanowitz
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Donald F Hunt
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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Santos IC, Brodbelt JS. Structural Characterization of Carbonic Anhydrase-Arylsulfonamide Complexes Using Ultraviolet Photodissociation Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1370-1379. [PMID: 33683877 PMCID: PMC8377746 DOI: 10.1021/jasms.1c00004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Numerous mass spectrometry-based strategies ranging from hydrogen-deuterium exchange to ion mobility to native mass spectrometry have been developed to advance biophysical and structural characterization of protein conformations and determination of protein-ligand interactions. In this study, we focus on the use of ultraviolet photodissociation (UVPD) to examine the structure of human carbonic anhydrase II (hCAII) and its interactions with arylsulfonamide inhibitors. Carbonic anhydrase, which catalyzes the conversion of carbon dioxide to bicarbonate, has been the target of countless thermodynamic and kinetic studies owing to its well-characterized active site, binding cavity, and mechanism of inhibition by hundreds of ligands. Here, we showcase the application of UVPD for evaluating structural changes of hCAII upon ligand binding on the basis of variations in fragmentation of hCAII versus hCAII-arylsulfonamide complexes, particularly focusing on the hydrophobic pocket. To extend the coverage in the midregion of the protein sequence, a supercharging agent was added to the solutions to increase the charge states of the complexes. The three arylsulfonamides examined in this study largely shift the fragmentation patterns in similar ways, despite their differences in binding affinities.
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Affiliation(s)
- Inês C Santos
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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Cejkov M, Greer T, Johnson RO, Zheng X, Li N. Electron Transfer Dissociation Parameter Optimization Using Design of Experiments Increases Sequence Coverage of Monoclonal Antibodies. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:762-771. [PMID: 33596068 DOI: 10.1021/jasms.0c00458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Middle-down analysis of monoclonal antibodies (mAbs) by tandem mass spectrometry (MS2) can provide detailed insight into their primary structure with minimal sample preparation. The middle-down approach uses an enzyme to cleave mAbs into Fc/2, LC, and Fd subunits that are then analyzed by reversed phase liquid chromatography tandem mass spectrometry (RPLC-MS2). As maximum sequence coverage is desired to obtain meaningful structural information at the subunit level, a host of dissociation methods have been developed, and sometimes combined, to bolster fragmentation and increase the number of identified fragments. Here, we present a design of experiments (DOE) approach to optimize MS2 parameters, in particular those that may influence electron transfer dissociation (ETD) efficiency to increase the sequence coverage of antibody subunits. Applying this approach to the NIST monoclonal antibody standard (NISTmAb) using three RPLC-MS2 runs resulted in high sequence coverages of 67%, 67%, and 52% for Fc/2, LC, and Fd subunits, respectively. In addition, we apply this DOE strategy to model the parameters required to maximize the number of fragments produced in "low", "medium", and "high" mass ranges, which ultimately resulted in even higher sequence coverages of NISTmAb subunits (75%, 78%, and 64% for Fc/2, LC, and Fd subunits, respectively). The DOE approach provides high sequence coverage percentages utilizing only one fragmentation method, ETD, and could be extended to other state-of-the-art techniques that combine multiple fragmentation mechanisms to increase coverage.
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Affiliation(s)
- Milos Cejkov
- Analytical Chemistry, Regeneron Pharmaceuticals Inc., 777 Old Saw Mill River Road, Tarrytown, New York 10591-6707, United States
| | - Tyler Greer
- Analytical Chemistry, Regeneron Pharmaceuticals Inc., 777 Old Saw Mill River Road, Tarrytown, New York 10591-6707, United States
| | - Reid O'Brien Johnson
- Analytical Chemistry, Regeneron Pharmaceuticals Inc., 777 Old Saw Mill River Road, Tarrytown, New York 10591-6707, United States
| | - Xiaojing Zheng
- Analytical Chemistry, Regeneron Pharmaceuticals Inc., 777 Old Saw Mill River Road, Tarrytown, New York 10591-6707, United States
| | - Ning Li
- Analytical Chemistry, Regeneron Pharmaceuticals Inc., 777 Old Saw Mill River Road, Tarrytown, New York 10591-6707, United States
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Brown KA, Tucholski T, Alpert AJ, Eken C, Wesemann L, Kyrvasilis A, Jin S, Ge Y. Top-Down Proteomics of Endogenous Membrane Proteins Enabled by Cloud Point Enrichment and Multidimensional Liquid Chromatography-Mass Spectrometry. Anal Chem 2020; 92:15726-15735. [PMID: 33231430 PMCID: PMC7968110 DOI: 10.1021/acs.analchem.0c02533] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Although top-down proteomics has emerged as a powerful strategy to characterize proteins in biological systems, the analysis of endogenous membrane proteins remains challenging due to their low solubility, low abundance, and the complexity of the membrane subproteome. Here, we report a simple but effective enrichment and separation strategy for top-down proteomics of endogenous membrane proteins enabled by cloud point extraction and multidimensional liquid chromatography coupled to high-resolution mass spectrometry (MS). The cloud point extraction efficiently enriched membrane proteins using a single extraction, eliminating the need for time-consuming ultracentrifugation steps. Subsequently, size-exclusion chromatography (SEC) with an MS-compatible mobile phase (59% water, 40% isopropanol, 1% formic acid) was used to remove the residual surfactant and fractionate intact proteins (6-115 kDa). The fractions were separated further by reversed-phase liquid chromatography (RPLC) coupled with MS for protein characterization. This method was applied to human embryonic kidney cells and cardiac tissue lysates to enable the identification of 188 and 124 endogenous integral membrane proteins, respectively, some with as many as 19 transmembrane domains.
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Affiliation(s)
- Kyle A. Brown
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Trisha Tucholski
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Andrew J. Alpert
- PolyLC Inc., Columbia, Maryland 21045, United States
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
| | - Christian Eken
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Lucas Wesemann
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
| | - Andreas Kyrvasilis
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Ying Ge
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
- Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
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Watts E, Williams JD, Miesbauer LJ, Bruncko M, Brodbelt JS. Comprehensive Middle-Down Mass Spectrometry Characterization of an Antibody–Drug Conjugate by Combined Ion Activation Methods. Anal Chem 2020; 92:9790-9798. [DOI: 10.1021/acs.analchem.0c01232] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Eleanor Watts
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
| | | | | | - Milan Bruncko
- AbbVie, North Chicago, Illinois 60064-1802, United States
| | - Jennifer S. Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
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Foreman DJ, Bhanot J, Lee KW, McLuckey SA. Valet Parking for Protein Ion Charge State Concentration: Ion/Molecule Reactions in Linear Ion Traps. Anal Chem 2020; 92:5419-5425. [PMID: 32100997 PMCID: PMC7145756 DOI: 10.1021/acs.analchem.0c00146] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
There are several analytical applications in which it is desirable to concentrate analyte ions generated over a range of charge states into a single charge state. This has been demonstrated in the gas phase via ion/ion reactions in conjunction with a technique termed ion parking, which can be implemented in electrodynamic ion traps. Ion parking depends upon the selective inhibition of the reaction of a selected charge state or charge states. In this work, we demonstrate a similar charge state concentration effect using ion/molecule reactions rather than ion/ion reactions. The rates of ion/molecule reactions cannot be affected in the manner used in conventional ion parking. Rather, to inhibit the progression of ion/molecule proton transfer reactions, the product ions must be removed from the reaction cell as they are formed and transferred to an ion trap where no reactions occur. This is accomplished here with mass-selective axial ejection (MSAE) from one linear ion trap to another. The application of MSAE to inhibit ion/molecule reactions is referred to as "valet parking" as it entails the transport of the ions of interest to a remote location for storage. Valet parking is demonstrated using model proteins to concentrate ion signal dispersed over multiple charge states into largely one charge state. Additionally, it has been applied to a simple two-protein mixture of cytochrome c and myoglobin.
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Affiliation(s)
- David J. Foreman
- Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA
| | - Jay Bhanot
- Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA
| | - Kenneth W. Lee
- Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA
| | - Scott A. McLuckey
- Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA
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Gallagher KJ, Palasser M, Hughes S, Mackay CL, Kilgour DPA, Clarke DJ. Isotope Depletion Mass Spectrometry (ID-MS) for Accurate Mass Determination and Improved Top-Down Sequence Coverage of Intact Proteins. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:700-710. [PMID: 32003978 DOI: 10.1021/jasms.9b00119] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Top-down mass spectrometry (MS) is an increasingly important technique for protein characterization. However, in many biological MS experiments, the practicality of applying top-down methodologies is still limited at higher molecular mass. In large part, this is due to the detrimental effect resulting from the partitioning of the mass spectral signal into an increasing number of isotopic peaks as molecular mass increases. Reducing the isotopologue distribution of proteins via depletion of heavy stable isotopes was first reported over 20 years ago (Marshall, A. G.; Senko, M. W.; Li, W.; Li, M.; Dillon, S., Guan, S.; Logan, T. M.. Protein Molecular Mass to 1 Da by 13C, 15N Double-Depletion and FT-ICR Mass Spectrometry. J. Am. Chem. Soc. 1997, 119, 433-434.) and has been demonstrated for several small proteins. Here we extend this approach, introducing a new highly efficient method for the production of recombinant proteins depleted in 13C and 15N and demonstrating its advantages for top-down analysis of larger proteins (up to ∼50 kDa). FT-ICR MS of isotopically depleted proteins reveals dramatically reduced isotope distributions with monoisotopic signal observed up to 50 kDa. In top-down fragmentation experiments, the reduced spectral complexity alleviates fragment-ion signal overlap, the presence of monoisotopic signals allows assignment with higher mass accuracy, and the dramatic increase in signal-to-noise ratio (up to 7-fold) permits vastly reduced acquisition times. These compounding benefits allow the assignment of ∼3-fold more fragment ions than comparable analyses of proteins with natural isotopic abundances. Finally, we demonstrate greatly increased sequence coverage in time-limited top-down experiments-highlighting advantages for top-down LC-MS/MS workflows and top-down proteomics.
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Affiliation(s)
- Kelly J Gallagher
- The EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Michael Palasser
- The EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Sam Hughes
- The EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, Brewster Road, Edinburgh EH9 3FJ, U.K
| | - C Logan Mackay
- The EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, Brewster Road, Edinburgh EH9 3FJ, U.K
| | - David P A Kilgour
- Chemistry and Forensics, Nottingham Trent University, Rosalind Franklin Building, Clifton Lane, Nottingham NG11 8NS, U.K
| | - David J Clarke
- The EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, Brewster Road, Edinburgh EH9 3FJ, U.K
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