1
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Brandner S, Habeck T, Lermyte F. New Insights into the Intrinsic Electron-Based Dissociation Behavior of Cytochrome c Oligomers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1908-1916. [PMID: 37227392 DOI: 10.1021/jasms.3c00106] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Between 2003 and 2017, four reports were published that demonstrated the intrinsic ability of the native iron-containing proteins cytochrome c and ferritin to undergo radical-based backbone fragmentation in the gas phase without the introduction of exogenous electrons. For cytochrome c in particular, this effect has so far only been reported to occur in the ion source, preventing the in-depth study of reactions occurring after gas-phase isolation of specific precursors. Here, we report the first observation of this intrinsic native electron capture dissociation behavior after quadrupole isolation of specific charge states of the cytochrome c dimer and trimer, providing direct experimental support for key aspects of the mechanism proposed 20 years ago. Furthermore, we provide evidence that, in contrast to some earlier proposals, these oligomeric states are formed in bulk solution rather than during the electrospray ionization process and that the observed fragmentation site preferences can be rationalized through the structure and interactions within these native oligomers rather than the monomer. We also show that the observed fragmentation pattern─and indeed, whether or not fragmentation occurs─is highly sensitive to the provenance and history of the protein samples, to the extent that samples can show distinct fragmentation behavior despite behaving identically in ion mobility experiments. This rather underexplored method therefore represents an exquisitely sensitive conformational probe and will hopefully receive more attention from the biomolecular mass spectrometry community in the future.
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Affiliation(s)
- Sarah Brandner
- Department of Chemistry, Clemens-Schöpf Institute of Organic Chemistry and Biochemistry, Technical University of Darmstadt, Peter-Grünberg-Strasse 4, 64287 Darmstadt, Germany
| | - Tanja Habeck
- Department of Chemistry, Clemens-Schöpf Institute of Organic Chemistry and Biochemistry, Technical University of Darmstadt, Peter-Grünberg-Strasse 4, 64287 Darmstadt, Germany
| | - Frederik Lermyte
- Department of Chemistry, Clemens-Schöpf Institute of Organic Chemistry and Biochemistry, Technical University of Darmstadt, Peter-Grünberg-Strasse 4, 64287 Darmstadt, Germany
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2
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Shoff TA, Julian RR. Fragment Ion Abundance Reveals Information about Structure and Charge Localization in Highly Charged Proteins. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023. [PMID: 37477985 PMCID: PMC10401701 DOI: 10.1021/jasms.3c00196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Top-down mass spectrometry (MS) is a versatile tool that has been employed to investigate both protein sequence and structure. Although a variety of different fragmentation methods are available in top-down MS that can potentially yield structural information, quantifying differences between spectra remains challenging. Herein, we show that subtle differences in spectra produced by a variety of fragmentation methods are surprisingly sensitive to protein structure and/or charge localization, even in highly unfolded proteins observed in high charge states. In addition to exposing information about the protein structure, differences in fragmentation also reveal insight into the mechanisms underlying the dissociation methods themselves. The results further reveal that small changes in experimental parameters (such as the addition of methanol instead of acetonitrile) lead to changes in structure that are reflected in statistically reproducible differences in dissociation. Collisional annealing of structurally dissimilar ions in the gas phase eventually leads to dissociation spectra that are indistinguishable, suggesting that structural differences can be erased by sufficient thermal activation. Additional experiments illustrate that identical charge states of the same protein can be distinguished if those produced directly by electrospray are compared to ions manipulated by in vacuo proton-transfer charge reduction. Overall, the results show that subtle differences in both three-dimensional structure and charge-site localization can influence the abundance of fragment ions produced by top-down MS, including dissociation methods not typically thought to be structurally sensitive.
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Affiliation(s)
- Thomas A Shoff
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Ryan R Julian
- Department of Chemistry, University of California, Riverside, California 92521, United States
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3
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Luan M, Hou Z, Huang G. Suppression of Protein Structural Perturbations in Native Electrospray Ionization during the Final Evaporation Stages Revealed by Molecular Dynamics Simulations. J Phys Chem B 2021; 126:144-150. [PMID: 34964355 DOI: 10.1021/acs.jpcb.1c09130] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Native electrospray ionization was known to preserve the protein structure in solution, which overcame the uncontrollable acidification of droplets during transfer from solution into the gas phase in conventional electrospray ionization. However, detailed experimental studies on when and how could native electrospray ionization minimize structural perturbations remain quite unclear. Herein, we conducted molecular dynamics simulations to investigate the protein structure evolution during electrospray ionization. At a neutral droplet pH, the protein structure in solution could be retained after evaporation, which was in accordance with previous reports. As the droplet pH deviated from neutral, we have found that the compact protein structure would not unfold until the last 10 ns prior to the final desolvation, which demonstrated that the role of native electrospray ionization in preserving the protein structure was mainly reflected on the final evaporation stages. The present study might provide new insights into studying the microscopic biomolecular events occurring during the liquid-gas interface transition and their influence on solution-structure retention.
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Affiliation(s)
- Moujun Luan
- The First Affiliated Hospital of USTC, University of Science and Technology of China, 230001 Hefei, China.,School of Chemistry and Materials Science, University of Science and Technology of China, 230026 Hefei, China
| | - Zhuanghao Hou
- The First Affiliated Hospital of USTC, University of Science and Technology of China, 230001 Hefei, China.,School of Chemistry and Materials Science, University of Science and Technology of China, 230026 Hefei, China.,National Synchrotron Radiation Laboratory, University of Science and Technology of China, 230029 Hefei, China
| | - Guangming Huang
- The First Affiliated Hospital of USTC, University of Science and Technology of China, 230001 Hefei, China.,School of Chemistry and Materials Science, University of Science and Technology of China, 230026 Hefei, China.,National Synchrotron Radiation Laboratory, University of Science and Technology of China, 230029 Hefei, China
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4
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Barth M, Schmidt C. Native mass spectrometry-A valuable tool in structural biology. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4578. [PMID: 32662584 DOI: 10.1002/jms.4578] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 05/18/2020] [Accepted: 05/19/2020] [Indexed: 05/16/2023]
Abstract
Proteins and the complexes they form with their ligands are the players of cellular action. Their function is directly linked with their structure making the structural analysis of protein-ligand complexes essential. Classical techniques of structural biology include X-ray crystallography, nuclear magnetic resonance spectroscopy and recently distinguished cryo-electron microscopy. However, protein-ligand complexes are often dynamic and heterogeneous and consequently challenging for these techniques. Alternative approaches are therefore needed and gained importance during the last decades. One alternative is native mass spectrometry, which is the analysis of intact protein complexes in the gas phase. To achieve this, sample preparation and instrument conditions have to be optimised. Native mass spectrometry then reveals stoichiometry, protein interactions and topology of protein assemblies. Advanced techniques such as ion mobility and high-resolution mass spectrometry further add to the range of applications and deliver information on shape and microheterogeneity of the complexes. In this tutorial, we explain the basics of native mass spectrometry including sample requirements, instrument modifications and interpretation of native mass spectra. We further discuss the developments of native mass spectrometry and provide example spectra and applications.
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Affiliation(s)
- Marie Barth
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Carla Schmidt
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Institute for Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle, Germany
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5
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Ives AN, Su T, Durbin KR, Early BP, Dos Santos Seckler H, Fellers RT, LeDuc RD, Schachner LF, Patrie SM, Kelleher NL. Using 10,000 Fragment Ions to Inform Scoring in Native Top-down Proteomics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:1398-1409. [PMID: 32436704 PMCID: PMC7539637 DOI: 10.1021/jasms.0c00026] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Protein fragmentation is a critical component of top-down proteomics, enabling gene-specific protein identification and full proteoform characterization. The factors that influence protein fragmentation include precursor charge, structure, and primary sequence, which have been explored extensively for collision-induced dissociation (CID). Recently, noticeable differences in CID-based fragmentation were reported for native versus denatured proteins, motivating the need for scoring metrics that are tailored specifically to native top-down mass spectrometry (nTDMS). To this end, position and intensity were tracked for 10,252 fragment ions produced by higher-energy collisional dissociation (HCD) of 159 native monomers and 70 complexes. We used published structural data to explore the relationship between fragmentation and protein topology and revealed that fragmentation events occur at a large range of relative residue solvent accessibility. Additionally, our analysis found that fragment ions at sites with an N-terminal aspartic acid or a C-terminal proline make up on average 40 and 27%, respectively, of the total matched fragment ion intensity in nTDMS. Percent intensity contributed by each amino acid was determined and converted into weights to (1) update the previously published C-score and (2) construct a native Fragmentation Propensity Score. Both scoring systems showed an improvement in protein identification or characterization in comparison to traditional methods and overall increased confidence in results with fewer matched fragment ions but with high probability nTDMS fragmentation patterns. Given the rise of nTDMS as a tool for structural mass spectrometry, we forward these scoring metrics as new methods to enhance analysis of nTDMS data.
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Affiliation(s)
- Ashley N Ives
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Taojunfeng Su
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Kenneth R Durbin
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
- Proteinaceous Inc., P.O. Box 1839, Evanston, Illinois 60204, United States
| | - Bryan P Early
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Henrique Dos Santos Seckler
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Ryan T Fellers
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
- Proteinaceous Inc., P.O. Box 1839, Evanston, Illinois 60204, United States
| | - Richard D LeDuc
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Luis F Schachner
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Steven M Patrie
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
| | - Neil L Kelleher
- Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, 2170 Campus Drive, Evanston, Illinois 60208, United States
- Proteinaceous Inc., P.O. Box 1839, Evanston, Illinois 60204, United States
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6
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Lermyte F, Tsybin YO, O'Connor PB, Loo JA. Top or Middle? Up or Down? Toward a Standard Lexicon for Protein Top-Down and Allied Mass Spectrometry Approaches. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:1149-1157. [PMID: 31073892 PMCID: PMC6591204 DOI: 10.1007/s13361-019-02201-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 03/13/2019] [Accepted: 03/14/2019] [Indexed: 05/18/2023]
Abstract
In recent years, there has been increasing interest in top-down mass spectrometry (TDMS) approaches for protein analysis, driven both by technological advancements and efforts such as those by the multinational Consortium for Top-Down Proteomics (CTDP). Today, diverse sample preparation and ionization methods are employed to facilitate TDMS analysis of denatured and native proteins and their complexes. The goals of these studies vary, ranging from protein and proteoform identification, to determination of the binding site of a (non)covalently-bound ligand, and in some cases even with the aim to study the higher order structure of proteins and complexes. Currently, however, no widely accepted terminology exists to precisely and unambiguously distinguish between the different types of TDMS experiments that can be performed. Instead, ad hoc developed terminology is often used, which potentially complicates communication of top-down and allied methods and their results. In this communication, we consider the different types of top-down (or top-down-related) MS experiments that have been performed and reported, and define distinct categories based on the protocol used and type(s) of information that can be obtained. We also consider the different possible conventions for distinguishing between middle- and top-down MS, based on both sample preparation and precursor ion mass. We believe that the proposed framework presented here will prove helpful for researchers to communicate about TDMS and will be an important step toward harmonizing and standardizing this growing field. Graphical Abstract.
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Affiliation(s)
- Frederik Lermyte
- School of Engineering, University of Warwick, Coventry, CV4 7AL, UK.
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
| | - Yury O Tsybin
- Spectroswiss, EPFL Innovation Park, 1015, Lausanne, Switzerland
| | - Peter B O'Connor
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, Department of Biological Chemistry, David Geffen School of Medicine, and UCLA/DOE Institute of Genomics and Proteomics, University of California, Los Angeles, CA, USA
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7
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Hu J, Lei W, Wang J, Chen HY, Xu JJ. Preservation of Protein Zwitterionic States in the Transition from Solution to Gas Phase Revealed by Sodium Adduction Mass Spectrometry. Anal Chem 2019; 91:7858-7863. [PMID: 31134800 DOI: 10.1021/acs.analchem.9b01602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structural characterization of proteins and their interaction network mapping in the gas phase highlights the need to preserve their most nativelike conformers in the transition from the solution to gas phase. Zwitterionic interactions in a protein are weak bonds between oppositely charged residues, which make an important contribution to protein stability. However, it is still not clear whether the native zwitterionic states of proteins can be retained or not when it is transferred from the solution to gas phase. Using the nonspecific Na+ adduction as a novel signature, here we show that the zwitterionic states of proteins can be preserved when a moderated droplet desolvation condition (temperature <30 °C) is used in native electrospray ionization mass spectrometry. The very low-level nonspecific metal adduction to proteins under such conditions also enables rapid and direct determination of the binding states of metal-binding proteins and sensitive detection of proteins from solutions containing highly concentrated involatile salts (e.g., 50 mM NaCl). We believe that our findings can be instructive for performing mass spectrometric analysis of proteins and useful for protein ions desalting which simply involves altering the temperature and flow rate of drying gas in the desolvation region.
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Affiliation(s)
- Jun Hu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Wen Lei
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Jiang Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Hong-Yuan Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Jing-Juan Xu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
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8
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Eldrid C, Ujma J, Kalfas S, Tomczyk N, Giles K, Morris M, Thalassinos K. Gas Phase Stability of Protein Ions in a Cyclic Ion Mobility Spectrometry Traveling Wave Device. Anal Chem 2019; 91:7554-7561. [PMID: 31117399 PMCID: PMC7006968 DOI: 10.1021/acs.analchem.8b05641] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
![]()
Ion
mobility mass spectrometry (IM-MS) allows separation of native
protein ions into “conformational families”. Increasing
the IM resolving power should allow finer structural information to
be obtained and can be achieved by increasing the length of the IM
separator. This, however, increases the time that protein ions spend
in the gas phase and previous experiments have shown that the initial
conformations of small proteins can be lost within tens of milliseconds.
Here, we report on investigations of protein ion stability using a
multipass traveling wave (TW) cyclic IM (cIM) device. Using this device,
minimal structural changes were observed for Cytochrome C after hundreds
of milliseconds, while no changes were observed for a larger multimeric
complex (Concanavalin A). The geometry of the instrument (Q-cIM-ToF)
also enables complex tandem IM experiments to be performed, which
were used to obtain more detailed collision-induced unfolding pathways
for Cytochrome C. The instrument geometry provides unique capabilities
with the potential to expand the field of protein analysis via IM-MS.
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Affiliation(s)
- Charles Eldrid
- Institute of Structural and Molecular Biology, Division of Biosciences , University College London , London , WC1E 6BT , United Kingdom
| | - Jakub Ujma
- Waters Corporation , Wilmslow , SK9 4AX , United Kingdom
| | - Symeon Kalfas
- Institute of Structural and Molecular Biology, Division of Biosciences , University College London , London , WC1E 6BT , United Kingdom
| | - Nick Tomczyk
- Waters Corporation , Wilmslow , SK9 4AX , United Kingdom
| | - Kevin Giles
- Waters Corporation , Wilmslow , SK9 4AX , United Kingdom
| | - Mike Morris
- Waters Corporation , Wilmslow , SK9 4AX , United Kingdom
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences , University College London , London , WC1E 6BT , United Kingdom.,Institute of Structural and Molecular Biology, Birkbeck College , University of London , London , WC1E 7HX , United Kingdom
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9
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Lermyte F, Valkenborg D, Loo JA, Sobott F. Radical solutions: Principles and application of electron-based dissociation in mass spectrometry-based analysis of protein structure. MASS SPECTROMETRY REVIEWS 2018; 37:750-771. [PMID: 29425406 PMCID: PMC6131092 DOI: 10.1002/mas.21560] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 01/19/2018] [Accepted: 01/19/2018] [Indexed: 05/11/2023]
Abstract
In recent years, electron capture (ECD) and electron transfer dissociation (ETD) have emerged as two of the most useful methods in mass spectrometry-based protein analysis, evidenced by a considerable and growing body of literature. In large part, the interest in these methods is due to their ability to induce backbone fragmentation with very little disruption of noncovalent interactions which allows inference of information regarding higher order structure from the observed fragmentation behavior. Here, we review the evolution of electron-based dissociation methods, and pay particular attention to their application in "native" mass spectrometry, their mechanism, determinants of fragmentation behavior, and recent developments in available instrumentation. Although we focus on the two most widely used methods-ECD and ETD-we also discuss the use of other ion/electron, ion/ion, and ion/neutral fragmentation methods, useful for interrogation of a range of classes of biomolecules in positive- and negative-ion mode, and speculate about how this exciting field might evolve in the coming years.
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Affiliation(s)
- Frederik Lermyte
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerp, Belgium
- Centre for Proteomics, University of Antwerp, Antwerp, Belgium
- School of Engineering, University of Warwick, Coventry, United Kingdom
| | - Dirk Valkenborg
- Centre for Proteomics, University of Antwerp, Antwerp, Belgium
- Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Agoralaan, Diepenbeek, Belgium
- Applied Bio and Molecular Systems, Flemish Institute for Technological Research (VITO), Mol, Belgium
| | - Joseph A Loo
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California
- UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, California
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California
| | - Frank Sobott
- Biomolecular and Analytical Mass Spectrometry Group, Department of Chemistry, University of Antwerp, Antwerp, Belgium
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, United Kingdom
- School of Molecular and Cellular Biology, University of Leeds, Leeds, United Kingdom
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10
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Schneeberger EM, Breuker K. Replacing H + by Na + or K + in phosphopeptide anions and cations prevents electron capture dissociation. Chem Sci 2018; 9:7338-7353. [PMID: 30542537 PMCID: PMC6237128 DOI: 10.1039/c8sc02470g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 07/07/2018] [Indexed: 01/29/2023] Open
Abstract
By successively replacing H+ by Na+ or K+ in phosphopeptide anions and cations, we show that the efficiency of fragmentation into c and z˙ or c˙ and z fragments from N-Cα backbone bond cleavage by negative ion electron capture dissociation (niECD) and electron capture dissociation (ECD) substantially decreases with increasing number of alkali ions attached. In proton-deficient phosphopeptide ions with a net charge of 2-, we observed an exponential decrease in electron capture efficiency with increasing number of Na+ or K+ ions attached, suggesting that electrons are preferentially captured at protonated sites. In proton-abundant phosphopeptide ions with a net charge of 3+, the electron capture efficiency was not affected by replacing up to four H+ ions with Na+ or K+ ions, but the yield of c, z˙ and c˙, z fragments from N-Cα backbone bond cleavage generally decreased next to Na+ or K+ binding sites. We interpret the site-specific decrease in fragmentation efficiency as Na+ or K+ binding to backbone amide oxygen in competition with interactions of protonated sites that would otherwise lead to backbone cleavage into c, z˙ or c˙, z fragments. Our findings seriously challenge the hypothesis that the positive charge responsible for ECD into c, z˙ or c˙, z fragments can generally be a sodium or other metal ion instead of a proton.
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Affiliation(s)
- Eva-Maria Schneeberger
- Institute of Organic Chemistry , Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80/82 , 6020 Innsbruck , Austria . ; http://www.bioms-breuker.at/
| | - Kathrin Breuker
- Institute of Organic Chemistry , Center for Molecular Biosciences Innsbruck (CMBI) , University of Innsbruck , Innrain 80/82 , 6020 Innsbruck , Austria . ; http://www.bioms-breuker.at/
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11
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Morrison LJ, Chai W, Rosenberg JA, Henkelman G, Brodbelt JS. Characterization of hydrogen bonding motifs in proteins: hydrogen elimination monitoring by ultraviolet photodissociation mass spectrometry. Phys Chem Chem Phys 2018; 19:20057-20074. [PMID: 28722742 DOI: 10.1039/c7cp04073c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Determination of structure and folding of certain classes of proteins remains intractable by conventional structural characterization strategies and has spurred the development of alternative methodologies. Mass spectrometry-based approaches have a unique capacity to differentiate protein heterogeneity due to the ability to discriminate populations, whether minor or major, featuring modifications or complexation with non-covalent ligands on the basis of m/z. Cleavage of the peptide backbone can be further utilized to obtain residue-specific structural information. Here, hydrogen elimination monitoring (HEM) upon ultraviolet photodissociation (UVPD) of proteins transferred to the gas phase via nativespray ionization is introduced as an innovative approach to deduce backbone hydrogen bonding patterns. Using well-characterized peptides and a series of proteins, prediction of the engagement of the amide carbonyl oxygen of the protein backbone in hydrogen bonding using UVPD-HEM is demonstrated to show significant agreement with the hydrogen-bonding motifs derived from molecular dynamics simulations and X-ray crystal structures.
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12
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Skinner OS, McAnally MO, Van Duyne RP, Schatz GC, Breuker K, Compton PD, Kelleher NL. Native Electron Capture Dissociation Maps to Iron-Binding Channels in Horse Spleen Ferritin. Anal Chem 2017; 89:10711-10716. [PMID: 28938074 PMCID: PMC5647560 DOI: 10.1021/acs.analchem.7b01581] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
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Native electron capture
dissociation (NECD) is a process during
which proteins undergo fragmentation similar to that from radical
dissociation methods, but without the addition of exogenous electrons.
However, after three initial reports of NECD from the cytochrome c dimer complex, no further evidence of the effect has been
published. Here, we report NECD behavior from horse spleen ferritin,
a ∼490 kDa protein complex ∼20-fold larger than the
previously studied cytochrome c dimer. Application
of front-end infrared excitation (FIRE) in conjunction with low- and
high-m/z quadrupole isolation and
collisionally activated dissociation (CAD) provides new insights into
the NECD mechanism. Additionally, activation of the intact complex
in either the electrospray droplet or the gas phase produced c-type fragment ions. Similar to the previously reported
results on cytochrome c, these fragment ions form
near residues known to interact with iron atoms in solution. By mapping
the location of backbone cleavages associated with c-type ions onto
the crystal structure, we are able to characterize two distinct iron
binding channels that facilitate iron ion transport into the core
of the complex. The resulting pathways are in good agreement with
previously reported results for iron binding sites in mammalian ferritin.
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Affiliation(s)
- Owen S Skinner
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Michael O McAnally
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Richard P Van Duyne
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - George C Schatz
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Kathrin Breuker
- Institute of Organic Chemistry, University of Innsbruck , A-6020 Innsbruck, Austria
| | - Philip D Compton
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Neil L Kelleher
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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13
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Straus RN, Jockusch RA. Probing the Gaseous Structure of a β-Hairpin Peptide with H/D Exchange and Electron Capture Dissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:358-369. [PMID: 27943124 DOI: 10.1007/s13361-016-1528-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 10/05/2016] [Accepted: 10/10/2016] [Indexed: 06/06/2023]
Abstract
An improved understanding of the extent to which native protein structure is retained upon transfer to the gas phase promises to enhance biological mass spectrometry, potentially streamlining workflows and providing fundamental insights into hydration effects. Here, we investigate the gaseous conformation of a model β-hairpin peptide using gas-phase hydrogen-deuterium (H/D) exchange with subsequent electron capture dissociation (ECD). Global gas-phase H/D exchange levels, and residue-specific exchange levels derived from ECD data, are compared among the wild type 16-residue peptide GB1p and several variants. High protection from H/D exchange observed for GB1p, but not for a truncated version, is consistent with the retention of secondary structure of GB1p in the gas phase or its refolding into some other compact structure. Four alanine mutants that destabilize the hairpin in solution show levels of protection similar to that of GB1p, suggesting collapse or (re)folding of these peptides upon transfer to the gas phase. These results offer a starting point from which to understand how a key secondary structural element, the β-hairpin, is affected by transfer to the gas phase. This work also demonstrates the utility of a much-needed addition to the tool set that is currently available for the investigation of the gaseous conformation of biomolecules, which can be employed in the future to better characterize gaseous proteins and protein complexes. Graphical Abstract ᅟ.
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Affiliation(s)
- Rita N Straus
- Department of Chemistry, University of Toronto, Toronto, ON, M5S 3H6, Canada
| | - Rebecca A Jockusch
- Department of Chemistry, University of Toronto, Toronto, ON, M5S 3H6, Canada.
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14
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Native Mass Spectrometry in Fragment-Based Drug Discovery. Molecules 2016; 21:molecules21080984. [PMID: 27483215 PMCID: PMC6274484 DOI: 10.3390/molecules21080984] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 07/14/2016] [Accepted: 07/23/2016] [Indexed: 11/17/2022] Open
Abstract
The advent of native mass spectrometry (MS) in 1990 led to the development of new mass spectrometry instrumentation and methodologies for the analysis of noncovalent protein-ligand complexes. Native MS has matured to become a fast, simple, highly sensitive and automatable technique with well-established utility for fragment-based drug discovery (FBDD). Native MS has the capability to directly detect weak ligand binding to proteins, to determine stoichiometry, relative or absolute binding affinities and specificities. Native MS can be used to delineate ligand-binding sites, to elucidate mechanisms of cooperativity and to study the thermodynamics of binding. This review highlights key attributes of native MS for FBDD campaigns.
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15
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Schennach M, Schneeberger EM, Breuker K. Unfolding and Folding of the Three-Helix Bundle Protein KIX in the Absence of Solvent. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1079-88. [PMID: 26936183 PMCID: PMC4863917 DOI: 10.1007/s13361-016-1363-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 02/04/2016] [Accepted: 02/05/2016] [Indexed: 05/11/2023]
Abstract
Electron capture dissociation was used to probe the structure, unfolding, and folding of KIX ions in the gas phase. At energies for vibrational activation that were sufficiently high to cause loss of small molecules such as NH3 and H2O by breaking of covalent bonds in about 5% of the KIX (M + nH)(n+) ions with n = 7-9, only partial unfolding was observed, consistent with our previous hypothesis that salt bridges play an important role in stabilizing the native solution fold after transfer into the gas phase. Folding of the partially unfolded ions on a timescale of up to 10 s was observed only for (M + nH)(n+) ions with n = 9, but not n = 7 and n = 8, which we attribute to differences in the distribution of charges within the (M + nH)(n+) ions. Graphical Abstract ᅟ.
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Affiliation(s)
- Moritz Schennach
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria
| | - Eva-Maria Schneeberger
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria
| | - Kathrin Breuker
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80/82, 6020, Innsbruck, Austria.
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16
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Compton PD, Fornelli L, Kelleher NL, Skinner OS. Probing Asymmetric Charge Partitioning of Protein Oligomers during Tandem Mass Spectrometry. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2015; 390:132-136. [PMID: 26692813 PMCID: PMC4673687 DOI: 10.1016/j.ijms.2015.08.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Dissociation of gaseous protein complexes produced by native electrospray often induces an asymmetric partitioning of charge between ejected subunits. We present a simple asymmetric charge partitioning factor (ACPF) to quantify the magnitude of asymmetry in this effect. When applied to monomer ejection from the cytochrome c dimer and β-amylase tetramer, we found that the ~60-70% of precursor charge ending up in the ejected monomers corresponds to ACPFs of 1.38 and 2.51, respectively. Further, we used site-specific fragmentation from electron transfer dissociation (ETD) to identify differences in fragmentation and characterize domains of secondary-structure present in the dimer, ejected monomers, and monomers obtained directly from electrospray ionization (ESI). We found evidence of structural changes between the dimer and ejected monomer, but also that the ejected monomer had a nearly identical set of fragment ions produced by ETD as the ESI monomer with the same charge state. Surprisingly, APCF values for ETD fragment ions generated directly from the dimer revealed that the fragments undergo asymmetric charge partitioning at over twice the magnitude of that observed for ejection of the monomer.
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Affiliation(s)
- Philip D. Compton
- Departments of Chemistry and Molecular Biosciences and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois 60208, USA
| | - Luca Fornelli
- Departments of Chemistry and Molecular Biosciences and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois 60208, USA
| | - Neil L. Kelleher
- Departments of Chemistry and Molecular Biosciences and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois 60208, USA
| | - Owen S. Skinner
- Departments of Chemistry and Molecular Biosciences and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois 60208, USA
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17
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Characterization of top-down ETD in a travelling-wave ion guide. Methods 2015; 89:22-9. [DOI: 10.1016/j.ymeth.2015.05.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 04/30/2015] [Accepted: 05/19/2015] [Indexed: 11/20/2022] Open
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18
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Lermyte F, Sobott F. Electron transfer dissociation provides higher-order structural information of native and partially unfolded protein complexes. Proteomics 2015; 15:2813-22. [DOI: 10.1002/pmic.201400516] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 03/13/2015] [Accepted: 06/15/2015] [Indexed: 12/31/2022]
Affiliation(s)
- Frederik Lermyte
- UA-VITO Center for Proteomics; University of Antwerp; Antwerp Belgium
- Biomolecular & Analytical Mass Spectrometry group; Department of Chemistry; University of Antwerp; Antwerp Belgium
| | - Frank Sobott
- UA-VITO Center for Proteomics; University of Antwerp; Antwerp Belgium
- Biomolecular & Analytical Mass Spectrometry group; Department of Chemistry; University of Antwerp; Antwerp Belgium
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19
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Zhang J, Ogorzalek Loo RR, Loo JA. Increasing Fragmentation of Disulfide-Bonded Proteins for Top-Down Mass Spectrometry by Supercharging. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2015; 377:546-556. [PMID: 26028988 PMCID: PMC4448141 DOI: 10.1016/j.ijms.2014.07.047] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The disulfide bond is an important post-translational modification to form and maintain the native structure and biological functions of proteins. Characterization of disulfide bond linkages is therefore of essential interest in the structural elucidation of proteins. Top-down mass spectrometry (MS) of disulfide-bonded proteins has been hindered by relatively low sequence coverage due to disulfide cross-linking. In this study, we employed top-down ESI-MS with Fourier-transform ion cyclotron resonance (FT-ICR) MS with electron capture dissociation (ECD) and collisionally activated dissociation (CAD) to study the fragmentation of supercharged proteins with multiple intramolecular disulfide bonds. With charge enhancement upon the addition of sulfolane to the analyte solution, improved protein fragmentation and disulfide bond cleavage efficiency was observed for proteins including bovine β-lactoglobulin, soybean trypsin inhibitor, human proinsulin, and chicken lysozyme. Both the number and relative abundances of product ions representing disulfide cleavage increase with increasing charge states for the proteins studied. Our studies suggest supercharging ESI-MS is a promising tool to aid in the top-down MS analysis of disulfide-bonded proteins, providing potentially useful information for the determination of disulfide bond linkages.
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Affiliation(s)
- Jiang Zhang
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California, 90095, United States
| | - Rachel R. Ogorzalek Loo
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, University of California-Los Angeles, Los Angeles, California, 90095, United States
- UCLA/DOE Institute for Genomics and Proteomics, 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
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, University of California-Los Angeles, Los Angeles, California, 90095, United States
- UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, California, 90095, United States
- Corresponding author. Tel.: +1 310 794 7023; fax: +1 310 206 4038. (J.A. Loo)
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20
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Rajabi K. Microsecond pulsed hydrogen/deuterium exchange of electrosprayed ubiquitin ions stored in a linear ion trap. Phys Chem Chem Phys 2015; 17:3607-16. [DOI: 10.1039/c4cp04716h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The pulsed HDX MS method is sampling a population of ubiquitin ions with a similar backbone fold as solution.
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Affiliation(s)
- Khadijeh Rajabi
- Department of Chemistry
- University of British Columbia (UBC)
- Vancouver
- Canada
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21
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Zhang Z, Browne SJ, Vachet RW. Exploring salt bridge structures of gas-phase protein ions using multiple stages of electron transfer and collision induced dissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:604-13. [PMID: 24496600 PMCID: PMC3963490 DOI: 10.1007/s13361-013-0821-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/23/2013] [Accepted: 12/23/2013] [Indexed: 05/07/2023]
Abstract
The gas-phase structures of protein ions have been studied by electron transfer dissociation (ETD) and collision-induced dissociation (CID) after electrospraying these proteins from native-like solutions into a quadrupole ion trap mass spectrometer. Because ETD can break covalent bonds while minimally disrupting noncovalent interactions, we have investigated the ability of this dissociation technique together with CID to probe the sites of electrostatic interactions in gas-phase protein ions. By comparing spectra from ETD with spectra from ETD followed by CID, we find that several proteins, including ubiquitin, CRABP I, azurin, and β-2-microglobulin, appear to maintain many of the salt bridge contacts known to exist in solution. To support this conclusion, we also performed calculations to consider all possible salt bridge patterns for each protein, and we find that the native salt bridge pattern explains the experimental ETD data better than nearly all other possible salt bridge patterns. Overall, our data suggest that ETD and ETD/CID of native protein ions can provide some insight into approximate location of salt bridges in the gas phase.
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22
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Liu J, Konermann L. Cation-induced stabilization of protein complexes in the gas phase: mechanistic insights from hemoglobin dissociation studies. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:595-603. [PMID: 24452299 DOI: 10.1007/s13361-013-0814-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 12/13/2013] [Accepted: 12/14/2013] [Indexed: 06/03/2023]
Abstract
Collision-induced dissociation (CID) of electrosprayed protein complexes usually involves asymmetric charge partitioning, where a single unfolded chain gets ejected that carries a disproportionately large fraction of charge. Using hemoglobin (Hb) tetramers as model system, we confirm earlier reports that bound metal ions can stabilize protein complexes under CID conditions. We examine the mechanism underlying this effect. Nonvolatile salts cause extensive adduct formation. Significant stabilization was observed for Mg(2+) and Ca(2+), whereas K(+), Rb(+), and Cs(+) had no effect. Precursor ion selection was used to examine Hb subpopulations with well-defined metal binding levels. K(+), Rb(+), and Cs(+)-adducted tetramers eject monomers that carry roughly one-quarter of the metal ions that were bound to the precursor. This demonstrates that charge migration during CID is exclusively due to proton transfer, not metal ion transfer. Also, replacement of highly mobile charge carriers (protons) with less mobile species (metal ions) does not exert a stabilizing influence under the conditions used here. Interestingly, Hb carrying stabilizing ions (Mg(2+) and Ca(2+)) generates monomeric CID products that are metal depleted. This effect is attributed to a combination of two factors: (1) Me(2+) binding stabilizes Hb via formation of chelation bridges (e.g., R-COO(-) Me(2+) (-)OOC-R); the more Me(2+) a subunit contains the more stable it is. (2) More than ~90% of the tetramers contain at least one subunit with a below-average number of Me(2+). The prevalence of monomeric CID products with depleted Me(2+) levels is caused by the tendency of these low metal-containing subunits to undergo preferential unfolding/ejection.
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Affiliation(s)
- JiangJiang Liu
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
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23
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Kalapothakis JMD, Berezovskaya Y, Zampronio CG, Faull PA, Barran PE, Cooper HJ. Unusual ECD fragmentation attributed to gas-phase helix formation in a conformationally dynamic peptide. Chem Commun (Camb) 2014; 50:198-200. [DOI: 10.1039/c3cc46356g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Schennach M, Breuker K. Proteins with Highly Similar Native Folds Can Show Vastly Dissimilar Folding Behavior When Desolvated. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201306838] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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25
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Schennach M, Breuker K. Proteins with highly similar native folds can show vastly dissimilar folding behavior when desolvated. Angew Chem Int Ed Engl 2013; 53:164-8. [PMID: 24259450 PMCID: PMC4065370 DOI: 10.1002/anie.201306838] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/07/2013] [Indexed: 01/08/2023]
Abstract
Proteins can be exposed to vastly different environments such as the cytosol or membranes, but the delicate balance between external factors and intrinsic determinants of protein structure, stability, and folding is only poorly understood. Here we used electron capture dissociation to study horse and tuna heart Cytochromes c in the complete absence of solvent. The significantly different stability of their highly similar native folds after transfer into the gas phase, and their strikingly different folding behavior in the gas phase, can be rationalized on the basis of electrostatic interactions such as salt bridges. In the absence of hydrophobic bonding, protein folding is far slower and more complex than in solution.
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Affiliation(s)
- Moritz Schennach
- Institut für Organische Chemie and Center for Molecular Biosciences Innsbruck (CMBI), Universität Innsbruck, Innrain 80-82, 6020 Innsbruck (Austria) http://www.bioms-breuker.at
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26
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Zhang H, Cui W, Gross ML. Native electrospray ionization and electron-capture dissociation for comparison of protein structure in solution and the gas phase. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2013; 354-355:10.1016/j.ijms.2013.06.019. [PMID: 24363606 PMCID: PMC3867139 DOI: 10.1016/j.ijms.2013.06.019] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The importance of protein and protein-complex structure motivates improvements in speed and sensitivity of structure determination in the gas phase and comparison with that in solution or solid state. An opportunity for the gas phase measurement is mass spectrometry (MS) combined with native electrospray ionization (ESI), which delivers large proteins and protein complexes in their near-native states to the gas phase. In this communication, we describe the combination of native ESI, electron-capture dissociation (ECD), and top-down MS for exploring the structures of ubiquitin and cytochrome c in the gas phase and their relation to those in the solid-state and solution. We probe structure by comparing the protein's flexible regions, as predicted by the B-factor in X-ray crystallography, with the ECD fragments. The underlying hypothesis is that maintenance of structure gives fragments that can be predicted from B-factors. This strategy may be applicable in general when X-ray structures are available and extendable to the study of intrinsically disordered proteins.
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Affiliation(s)
- Hao Zhang
- Department of Chemistry, Washington University, St. Louis, Missouri, 63130 USA
| | - Weidong Cui
- Department of Chemistry, Washington University, St. Louis, Missouri, 63130 USA
| | - Michael L Gross
- Department of Chemistry, Washington University, St. Louis, Missouri, 63130 USA
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27
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Vahidi S, Stocks BB, Konermann L. Partially Disordered Proteins Studied by Ion Mobility-Mass Spectrometry: Implications for the Preservation of Solution Phase Structure in the Gas Phase. Anal Chem 2013; 85:10471-8. [DOI: 10.1021/ac402490r] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Siavash Vahidi
- Departments
of Chemistry
and Biochemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Bradley B. Stocks
- Departments
of Chemistry
and Biochemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Lars Konermann
- Departments
of Chemistry
and Biochemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
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28
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Fully automated chip-based nanoelectrospray combined with electron transfer dissociation for high throughput top-down proteomics. OPEN CHEM 2013. [DOI: 10.2478/s11532-012-0130-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
AbstractThe conventional protocol for protein identification by electrospray ionization mass spectrometry (MS) is based on enzymatic digestion which renders peptides to be analyzed by liquid chromatography-MS and collision-induced dissociation (CID) multistage MS, in the so-called bottom-up approach. Though this method has brought a significant progress to the field, many limitations, among which, the low throughput and impossibility to characterize in detail posttranslational modifications in terms of site(s) and structure, were reported. Therefore, the research is presently focused on the development of procedures for efficient top-down fragmentation of intact protein ions. In this context, we developed here an approach combining fully automated chip-based-nanoelectrospray ionisation (nanoESI), performed on a NanoMate robot, with electron transfer dissociation (ETD) for peptide and top-down protein sequencing and identification. This advanced analytical platform, integrating robotics, microfluidics technology, ETD and alternate ETD/CID, was tested and found ideally suitable for structural investigation of peptides and modified/functionalized peptides as well as for top-down analysis of medium size proteins by tandem MS experiments of significantly increased throughput and sensitivity. The obtained results indicate that NanoMate-ETD and ETD/CID may represent a viable alternative to the current MS strategies, with potential to develop into a method of routine use for high throughput top-down proteomics.
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29
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Cassou CA, Sterling HJ, Susa AC, Williams ER. Electrothermal supercharging in mass spectrometry and tandem mass spectrometry of native proteins. Anal Chem 2012. [PMID: 23194134 DOI: 10.1021/ac302256d] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Electrothermal supercharging of protein ions formed by electrospray ionization from buffered aqueous solutions results in significant increases to both the maximum and average charge states compared to native mass spectrometry in which ions are formed from the same solutions but with lower spray potentials. For eight of the nine proteins investigated, the maximum charge states of protonated ions formed from native solutions with electrothermal supercharging is greater than those obtained from conventional denaturing solutions consisting of water/methanol/acid, although the average charging is slightly lower owing to contributions of small populations of more folded low charge-state structures. Under these conditions, electrothermal supercharging is slightly less effective for anions than for cations. Equivalent sequence coverage (80%) is obtained with electron transfer dissociation of the same high charge-state ion of cytochrome c formed by electrothermal supercharging from native solutions and from denaturing solutions. Electrothermal supercharging should be advantageous for combining structural studies of proteins in native environments with mass spectrometers that have limited high m/z capabilities and for significantly improving tandem mass spectrometry performance for protein ions formed from solutions in which the molecules have native structures and activities.
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Affiliation(s)
- Catherine A Cassou
- Department of Chemistry, University of California, Berkeley, 94720-1460, United States
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30
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Meyer T, Gabelica V, Grubmüller H, Orozco M. Proteins in the gas phase. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2012. [DOI: 10.1002/wcms.1130] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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31
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Hyung SJ, Ruotolo BT. Integrating mass spectrometry of intact protein complexes into structural proteomics. Proteomics 2012; 12:1547-64. [PMID: 22611037 DOI: 10.1002/pmic.201100520] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
MS analysis of intact protein complexes has emerged as an established technology for assessing the composition and connectivity within dynamic, heterogeneous multiprotein complexes at low concentrations and in the context of mixtures. As this technology continues to move forward, one of the main challenges is to integrate the information content of such intact protein complex measurements with other MS approaches in structural biology. Methods such as H/D exchange, oxidative foot-printing, chemical cross-linking, affinity purification, and ion mobility separation add complementary information that allows access to every level of protein structure and organization. Here, we survey the structural information that can be retrieved by such experiments, demonstrate the applicability of integrative MS approaches in structural proteomics, and look to the future to explore upcoming innovations in this rapidly advancing area.
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Affiliation(s)
- Suk-Joon Hyung
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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32
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Hall Z, Robinson CV. Do charge state signatures guarantee protein conformations? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1161-8. [PMID: 22562394 DOI: 10.1007/s13361-012-0393-z] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 05/11/2023]
Abstract
The extent to which proteins in the gas phase retain their condensed-phase structure is a hotly debated issue. Closely related to this is the degree to which the observed charge state reflects protein conformation. Evidence from electron capture dissociation, hydrogen/deuterium exchange, ion mobility, and molecular dynamics shows clearly that there is often a strong correlation between the degree of folding and charge state, with the most compact conformations observed for the lowest charge states. In this article, we address recent controversies surrounding the relationship between charge states and folding, focussing also on the manipulation of charge in solution and its effect on conformation. 'Supercharging' reagents that have been used to effect change in charge state can promote unfolding in the electrospray droplet. However for several protein complexes, supercharging does not appear to perturb the structure in that unfolding is not detected. Consequently, a higher charge state does not necessarily imply unfolding. Whilst the effect of charge manipulation on conformation remains controversial, there is strong evidence that a folded, compact state of a protein can survive in the gas phase, at least on a millisecond timescale. The exact nature of the side-chain packing and secondary structural elements in these compact states, however, remains elusive and prompts further research.
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Affiliation(s)
- Zoe Hall
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK
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33
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Skinner OS, McLafferty FW, Breuker K. How ubiquitin unfolds after transfer into the gas phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1011-4. [PMID: 22476890 PMCID: PMC3345118 DOI: 10.1007/s13361-012-0370-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Revised: 02/29/2012] [Accepted: 03/02/2012] [Indexed: 05/11/2023]
Abstract
The structural evolution of ubiquitin after transfer into the gas phase was studied by electron capture dissociation. Site-specific fragment yields show that ubiquitin's solution fold is overall unstable in the gas phase, but unfolding caused by loss of solvent is slowest in regions stabilized by salt bridges.
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Affiliation(s)
- Owen S. Skinner
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 USA
| | - Fred W. McLafferty
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 USA
| | - Kathrin Breuker
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
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34
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Zhang Y, Cui W, Zhang H, Dewald HD, Chen H. Electrochemistry-assisted top-down characterization of disulfide-containing proteins. Anal Chem 2012; 84:3838-42. [PMID: 22448817 DOI: 10.1021/ac300106y] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Covalent disulfide bond linkage in a protein represents an important challenge for mass spectrometry (MS)-based top-down protein structure analysis as it reduces the backbone cleavage efficiency for MS/MS dissociation. This study presents a strategy for solving this critical issue via integrating electrochemistry (EC) online with a top-down MS approach. In this approach, proteins undergo electrolytic reduction in an electrochemical cell to break disulfide bonds and then undergo online ionization into gaseous ions for analysis by electron-capture dissociation (ECD) and collision-induced dissociation (CID). The electrochemical reduction of proteins allows one to remove disulfide bond constraints and also leads to increased charge numbers of the resulting protein ions. As a result, sequence coverage was significantly enhanced, as exemplified by β-lactoglobulin A (24 vs 75 backbone cleavages before and after electrolytic reduction, respectively) and lysozyme (5 vs 66 backbone cleavages before and after electrolytic reduction, respectively). This methodology is fast and does not need chemical reductants, which would have an important impact in high-throughput proteomics research.
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Affiliation(s)
- Yun Zhang
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
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35
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Brunet C, Antoine R, Lemoine J, Dugourd P. Soret Band of the Gas-Phase Ferri-Cytochrome c. J Phys Chem Lett 2012; 3:698-702. [PMID: 26286275 DOI: 10.1021/jz300070r] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report the first visible spectrum of a heme-protein in the gas phase. The aim of this work was to provide a reference for the optical absorption of an isolated heme-protein to better understand the influence of protein conformation and fluctuation and of solvent on its optical properties. After laser irradiation of gas-phase cytochrome c (cyt c), electron emission is observed. Electron photodetachment yield of cyt c 6- was recorded in the region of the Soret band of the porphyrin group, showing a maximum at 410 nm. Our results are compared with optical spectra of gas-phase heme and of cyt c in solution. We discuss the influence of the polypeptide chain and of the solvent on both the position and the broadening of the Soret band. Action spectrum of gas-phase cyt c is close to the absorption of native cyt c in solution, suggesting an efficient protection of the heme group from solvent accessibility by the polypeptide chain and similar interactions between the two moieties in solution and the gas phase.
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Affiliation(s)
- Claire Brunet
- †Université Lyon 1, Lyon, France
- ‡CNRS, LASIM UMR 5579, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France
- §CNRS, Institut des Sciences Analytique UMR 5180, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France
| | - Rodolphe Antoine
- †Université Lyon 1, Lyon, France
- ‡CNRS, LASIM UMR 5579, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France
| | - Jérôme Lemoine
- †Université Lyon 1, Lyon, France
- §CNRS, Institut des Sciences Analytique UMR 5180, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France
| | - Philippe Dugourd
- †Université Lyon 1, Lyon, France
- ‡CNRS, LASIM UMR 5579, 43 bd du 11 novembre 1918, 69622 Villeurbanne Cedex, France
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36
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Rand KD, Pringle SD, Morris M, Brown JM. Site-Specific Analysis of Gas-Phase Hydrogen/Deuterium Exchange of Peptides and Proteins by Electron Transfer Dissociation. Anal Chem 2012; 84:1931-40. [DOI: 10.1021/ac202918j] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Kasper D. Rand
- The Department of
Pharmaceutics
and Analytical Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Steven D. Pringle
- Waters
MS Technologies Centre, Micromass U.K. Ltd., Floats Rd, Wythenshawe, Manchester
M23 9LZ, U.K
| | - Michael Morris
- Waters
MS Technologies Centre, Micromass U.K. Ltd., Floats Rd, Wythenshawe, Manchester
M23 9LZ, U.K
| | - Jeffery M. Brown
- Waters
MS Technologies Centre, Micromass U.K. Ltd., Floats Rd, Wythenshawe, Manchester
M23 9LZ, U.K
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37
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Cui W, Rohrs HW, Gross ML. Top-down mass spectrometry: recent developments, applications and perspectives. Analyst 2011; 136:3854-64. [PMID: 21826297 PMCID: PMC3505190 DOI: 10.1039/c1an15286f] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Top-down mass spectrometry is an emerging approach for the analysis of intact proteins. The term was coined as a contrast with the better-established, bottom-up strategy for analysis of peptide fragments derived from digestion, either enzymatically or chemically, of intact proteins. Although the term top-down originates from proteomics, it can also be applied to mass spectrometric analysis of intact large biomolecules that are constituents of protein assemblies or complexes. Traditionally, mass spectrometry has usually started with intact molecules, and in this regard, top-down approaches reflect the spirit of mass spectrometry. This article provides an overview of the methodologies in top-down mass spectrometry and then reviews applications covering protein posttranslational modifications, protein biophysics, DNAs/RNAs, and protein assemblies. Finally, challenges and future directions are discussed.
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Affiliation(s)
- Weidong Cui
- NIH NCRR Center for Biomedical and Bio-Organic Mass Spectrometry, Department of Chemistry, Washington University, St. Louis, MO 63130, USA.
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38
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Breuker K, Brüschweiler S, Tollinger M. Electrostatic Stabilization of a Native Protein Structure in the Gas Phase. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201005112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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39
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Breuker K, Brüschweiler S, Tollinger M. Electrostatic stabilization of a native protein structure in the gas phase. Angew Chem Int Ed Engl 2010; 50:873-7. [PMID: 21246681 PMCID: PMC3045662 DOI: 10.1002/anie.201005112] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Indexed: 11/17/2022]
Affiliation(s)
- Kathrin Breuker
- Institut für Organische Chemie and Center for Molecular Biosciences Innsbruck, Universität Innsbruck, Innrain 52a, 6020 Innsbruck, Austria.
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40
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Zhao Q, Schieffer GM, Soyk MW, Anderson TJ, Houk RS, Badman ER. Effects of ion/ion proton transfer reactions on conformation of gas-phase cytochrome c ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1208-1217. [PMID: 20430642 DOI: 10.1016/j.jasms.2010.03.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 03/11/2010] [Accepted: 03/12/2010] [Indexed: 05/29/2023]
Abstract
Positive ions from cytochrome c are studied in a 3-D ion trap/ion mobility (IM)/quadrupole-time-of-flight (TOF) instrument with three independent ion sources. The IM separation allows measurement of the cross section of the ions. Ion/ion reactions in the 3-D ion trap that remove protons cause the cytochrome c ions to refold gently without other degradation of protein structure, i.e., fragmentation or loss of heme group or metal ion. The conformation(s) of the product ions generated by ion/ion reactions in a given charge state are similar regardless of whether the cytochrome c ions are originally in +8 or +9 charge states. In the lower charge states (+1 to +5) cytochrome c ions made by the ion/ion reaction yield a single IM peak with cross section of approximately 1110 to 1180 A(2), even if the original +8 ion started with multiple conformations. The conformation expands slightly when the charge state is reduced from +5 to +1. For product ions in the +6 to +8 charge states, ions created from higher charge states (+9 to +16) by ion/ion reaction produce more compact conformation(s) in somewhat higher abundances compared with those produced directly by the electrospray ionization (ESI) source. For ions in intermediate charge states that have a variety of resolvable conformers, the voltage used to inject the ions into the drift tube, and the voltage and duration of the pulse that extracts ions from the ion trap, can affect the observed abundances of various conformers.
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Affiliation(s)
- Qin Zhao
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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41
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Yin S, Loo JA. Elucidating the site of protein-ATP binding by top-down mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:899-907. [PMID: 20163968 DOI: 10.1016/j.jasms.2010.01.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 01/08/2010] [Accepted: 01/08/2010] [Indexed: 05/11/2023]
Abstract
A Fourier-transform ion cyclotron resonance (FT-ICR) top-down mass spectrometry strategy for determining the adenosine triphosphate (ATP)-binding site on chicken adenylate kinase is described. Noncovalent protein-ligand complexes are readily detected by electrospray ionization mass spectrometry (ESI-MS), but the ability to detect protein-ligand complexes depends on their stability in the gas phase. Previously, we showed that collisionally activated dissociation (CAD) of protein-nucleotide triphosphate complexes yield products from the dissociation of a covalent phosphate bond of the nucleotide with subsequent release of the nucleotide monophosphate (Yin, S. et al., J. Am. Soc. Mass Spectrom. 2008, 19, 1199-1208). The intrinsic stability of electrostatic interactions in the gas phase allows the diphosphate group to remain noncovalently bound to the protein. This feature is exploited to yield positional information on the site of ATP-binding on adenylate kinase. CAD and electron capture dissociation (ECD) of the adenylate kinase-ATP complex generate product ions bearing mono- and diphosphate groups from regions previously suggested as the ATP-binding pocket by NMR and crystallographic techniques. Top-down MS may be a viable tool to determine the ATP-binding sites on protein kinases and identify previously unknown protein kinases in a functional proteomics study.
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Affiliation(s)
- Sheng Yin
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, USA
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42
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Bich C, Baer S, Jecklin MC, Zenobi R. Probing the hydrophobic effect of noncovalent complexes by mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:286-289. [PMID: 19931466 DOI: 10.1016/j.jasms.2009.10.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2009] [Revised: 10/15/2009] [Accepted: 10/15/2009] [Indexed: 05/28/2023]
Abstract
The study of noncovalent interactions by mass spectrometry has become an active field of research in recent years. The role of the different noncovalent intermolecular forces is not yet fully understood since they tend to be modulated upon transfer into the gas phase. The hydrophobic effect, which plays a major role in protein folding, adhesion of lipid bilayers, etc., is absent in the gas phase. Here, noncovalent complexes with different types of interaction forces were investigated by mass spectrometry and compared with the complex present in solution. Creatine kinase (CK), glutathione S-transferase (GST), ribonuclease S (RNase S), and leucine zipper (LZ), which have dissociation constants in the nM range, were studied by native nanoelectrospray mass spectrometry (nanoESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with chemical cross-linking (XL). Complexes interacting with hydrogen bonds survived the transfer into gas phase intact and were observed by nanoESI-MS. Complexes that are bound largely by the hydrophobic effect in solution were not detected or only at very low intensity. Complexes with mixed polar and hydrophobic interactions were detected by nanoESI-MS, most likely due to the contribution from polar interactions. All noncovalent complexes could easily be studied by XL MALDI-MS, which demonstrates that the noncovalently bound complexes are conserved, and a real "snap-shot" of the situation in solution can be obtained.
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Affiliation(s)
- Claudia Bich
- Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland
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43
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Chingin K, Frankevich V, Balabin R, Barylyuk K, Chen H, Wang R, Zenobi R. Direct Access to Isolated Biomolecules under Ambient Conditions. Angew Chem Int Ed Engl 2010; 49:2358-61. [DOI: 10.1002/anie.200906213] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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44
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Chingin K, Frankevich V, Balabin R, Barylyuk K, Chen H, Wang R, Zenobi R. Direct Access to Isolated Biomolecules under Ambient Conditions. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200906213] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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45
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McLafferty FW, Castro S, Breuker K. Multi-step evolution of protein conformation on electrospray into the gas phase. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2010; 16:437-442. [PMID: 20530828 DOI: 10.1255/ejms.1058] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In the gas phase, some properties of native versus denatured protein conformations correspond to those in solution, such as affinity for protons and physical cross section. However, the capacity for hydrogen/deutrerium exchange is the opposite, with ubiquitin 7+ and 13+ ions exchanging >-60 D and approximately 15 D atoms, respectively. A variety of experimental methods now delineate a series of conformational perturbations that can occur in the 10(-12) s to 10(+2) s following electrospray, including side-chain collapse, hydrophobic and electrostatic non-covalent bond unfolding and refolding into a variety of non-native structures.
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Affiliation(s)
- Fred W McLafferty
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301, USA.
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46
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Zhao Q, Soyk MW, Schieffer GM, Fuhrer K, Gonin MM, Houk RS, Badman ER. An ion trap-ion mobility-time of flight mass spectrometer with three ion sources for ion/ion reactions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:1549-1561. [PMID: 19493684 DOI: 10.1016/j.jasms.2009.04.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 04/17/2009] [Accepted: 04/17/2009] [Indexed: 05/27/2023]
Abstract
This instrument combines the capabilities of ion/ion reactions with ion mobility (IM) and time-of-flight (TOF) measurements for conformation studies and top-down analysis of large biomolecules. Ubiquitin ions from either of two electrospray ionization (ESI) sources are stored in a three dimensional (3D) ion trap (IT) and reacted with negative ions from atmospheric sampling glow discharge ionization (ASGDI). The proton transfer reaction products are then separated by IM and analyzed via a TOF mass analyzer. In this way, ubiquitin +7 ions are converted to lower charge states down to +1; the ions in lower charge states tend to be in compact conformations with cross sections down to approximately 880 A(2). The duration and magnitude of the ion ejection pulse on the IT exit and the entrance voltage on the IM drift tube can affect the measured distribution of conformers for ubiquitin +7 and +6. Alternatively, protein ions are fragmented by collision-induced dissociation (CID) in the IT, followed by ion/ion reactions to reduce the charge states of the CID product ions, thus simplifying assignment of charge states and fragments using the mobility-resolved tandem mass spectrum. Instrument characteristics and the use of a new ion trap controller and software modifications to control the entire instrument are described.
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Affiliation(s)
- Qin Zhao
- Department of Chemistry, Iowa State University, Ames, Iowa, USA
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47
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Stepwise evolution of protein native structure with electrospray into the gas phase, 10(-12) to 10(2) s. Proc Natl Acad Sci U S A 2009; 105:18145-52. [PMID: 19033474 DOI: 10.1073/pnas.0807005105] [Citation(s) in RCA: 348] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mass spectrometry (MS) has been revolutionized by electrospray ionization (ESI), which is sufficiently "gentle" to introduce nonvolatile biomolecules such as proteins and nucleic acids (RNA or DNA) into the gas phase without breaking covalent bonds. Although in some cases noncovalent bonding can be maintained sufficiently for ESI/MS characterization of the solution structure of large protein complexes and native enzyme/substrate binding, the new gaseous environment can ultimately cause dramatic structural alterations. The temporal (picoseconds to minutes) evolution of native protein structure during and after transfer into the gas phase, as proposed here based on a variety of studies, can involve side-chain collapse, unfolding, and refolding into new, non-native structures. Control of individual experimental factors allows optimization for specific research objectives.
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48
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Steinberg MZ, Elber R, McLafferty FW, Gerber RB, Breuker K. Early structural evolution of native cytochrome c after solvent removal. Chembiochem 2008; 9:2417-23. [PMID: 18785672 DOI: 10.1002/cbic.200800167] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electrospray ionization transfers thermally labile biomolecules, such as proteins, from solution into the gas phase, where they can be studied by mass spectrometry. Covalent bonds are generally preserved during and after the phase transition, but it is less clear to what extent noncovalent interactions are affected by the new gaseous environment. Here, we present atomic-level computational data on the structural rearrangement of native cytochrome c immediately after solvent removal. The first structural changes after desolvation occur surprisingly early, on a timescale of picoseconds. For the time segment of up to 4.2 ns investigated here, we observed no significant breaking of native noncovalent bonds; instead, we found formation of new noncovalent bonds. This generally involves charged residues on the protein surface, resulting in transiently stabilized intermediate structures with a global fold that is essentially the same as that in solution. Comparison with data from native electron capture dissociation experiments corroborates both its mechanistic postulations and our computational predictions, and suggests that global structural changes take place on a millisecond timescale not covered by our simulations.
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Affiliation(s)
- Michal Z Steinberg
- Department of Physical Chemistry, Fritz Haber Research Center, Hebrew University, Jerusalem 91904, Israel
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49
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Breuker K, Jin M, Han X, Jiang H, McLafferty FW. Top-down identification and characterization of biomolecules by mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:1045-53. [PMID: 18571936 PMCID: PMC2538795 DOI: 10.1016/j.jasms.2008.05.013] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2008] [Revised: 05/19/2008] [Accepted: 05/19/2008] [Indexed: 05/08/2023]
Abstract
The most widely used modern mass spectrometers face severe performance limitations with molecules larger than a few kDa. For far larger biomolecules, a common practice has been to break these up chemically or enzymatically into fragments that are sufficiently small for the instrumentation available. With its many sophisticated recent enhancements, this "bottom-up" approach has proved highly valuable, such as for the rapid, routine identification and quantitation of DNA-predicted proteins in complex mixtures. Characterization of smaller molecules, however, has always measured the mass of the molecule and then that of its fragments. This "top-down" approach has been made possible for direct analysis of large biomolecules by the uniquely high (>10(5)) mass resolving power and accuracy ( approximately 1 ppm) of the Fourier-transform mass spectrometer. For complex mixtures, isolation of a single component's molecular ions for MS/MS not only gives biomolecule identifications of far higher reliability, but directly characterizes sequence errors and post-translational modifications. Protein sizes amenable for current MS/MS instrumentation are increased by a "middle-down" approach in which limited proteolysis forms large (e.g., 10 kDa) polypeptides that are then subjected to the top-down approach, or by "prefolding dissociation." The latter, which extends characterization to proteins >200 kDa, was made possible by greater understanding of how molecular ion tertiary structure evolves in the gas phase.
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Affiliation(s)
- Kathrin Breuker
- Institute of Organic Chemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innrain 52a, 6020 Innsbruck, Austria
| | - Mi Jin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301
| | - Xuemei Han
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301
| | - Honghai Jiang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301
| | - Fred W. McLafferty
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301
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50
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Konermann L, Tong X, Pan Y. Protein structure and dynamics studied by mass spectrometry: H/D exchange, hydroxyl radical labeling, and related approaches. JOURNAL OF MASS SPECTROMETRY : JMS 2008; 43:1021-1036. [PMID: 18523973 DOI: 10.1002/jms.1435] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Mass spectrometry (MS) plays a central role in studies on protein structure and dynamics. This review highlights some of the recent developments in this area, with focus on applications involving the use of electrospray ionization (ESI) MS. Although this technique involves the transformation of analytes into highly nonphysiological species (desolvated gas-phase ions in the vacuum), ESI-MS can provide detailed insights into the solution-phase behavior of proteins. Notably, the ionization process itself occurs in a structurally sensitive manner. An increased degree of solution-phase unfolding is correlated with a higher level of protonation. Also, ESI allows the transfer of intact noncovalent complexes into the gas phase, thereby yielding information on binding partners, stoichiometries, and even affinities. A particular focus of this article is the use of hydrogen/deuterium exchange (HDX) methods and hydroxyl radical (.OH) labeling for monitoring dynamic and structural aspect of solution-phase proteins. Conceptual similarities and differences between the two methods are discussed. We describe a simple method for the computational simulation of protein HDX patterns, a tool that can be helpful for the interpretation of isotope exchange data recorded under mixed EX1/EX2 conditions. Important aspects of .OH labeling include a striking dependence on protein concentration, and the tendency of commonly used solvent additives to act as highly effective radical scavengers. If not properly controlled, both of these factors may lead to experimental artifacts.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada.
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