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Bashyal A, Hui JO, Flick T, Dykstra AB, Zhang Q, Campuzano IDG, Brodbelt JS. Differentiation of Aspartic and Isoaspartic Acid Using 193 nm Ultraviolet Photodissociation Mass Spectrometry. Anal Chem 2023; 95:11510-11517. [PMID: 37458293 PMCID: PMC10588209 DOI: 10.1021/acs.analchem.3c02025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Spontaneous conversion of aspartic acid (Asp) to isoaspartic acid (isoAsp) is a ubiquitous modification that influences the structure and function of proteins. This modification of Asp impacts the stability of biotherapeutics and has been linked to the development of neurodegenerative diseases. We explored the use of 193 nm ultraviolet photodissociation (UVPD) to distinguish Asp and isoAsp in the protonated and deprotonated peptides. The differences in the relative abundances of several fragment ions uniquely generated by UVPD were used to differentiate isomeric peptide standards containing Asp or isoAsp. These fragment ions result from the cleavage of bonds N-terminal to Asp/isoAsp residues in addition to the side-chain losses from Asp/isoAsp or the losses of COOH, CO2, CO, or H2O from y-ions. Fragmentation of Asp-containing tryptic peptides using UVPD resulted in more enhanced w/w + 1/y - 1/x ions, while isoAsp-containing peptides yielded more enhanced y - 18/y - 45/y - 46 ions. UVPD was also used to identify an isomerized peptide from a tryptic digest of a monoclonal antibody. Moreover, UVPD of a protonated nontryptic peptide resulted in more enhanced y ions N- and C-terminal to isoAsp and differences in b/y ion ratios that were used to identify the isoAsp peptide.
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Affiliation(s)
- Aarti Bashyal
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - John O Hui
- Amgen Research, Molecular Analytics, Amgen Inc., Thousand Oaks, California 91320, United States
| | - Tawnya Flick
- Process Development, Attribute Sciences, Amgen Inc., Thousand Oaks, California 91320, United States
| | - Andrew B Dykstra
- Process Development, Attribute Sciences, Amgen Inc., Thousand Oaks, California 91320, United States
| | - Qingchun Zhang
- Process Development, Attribute Sciences, Amgen Inc., Thousand Oaks, California 91320, United States
| | - Iain D G Campuzano
- Amgen Research, Molecular Analytics, Amgen Inc., Thousand Oaks, California 91320, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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2
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Lefebvre D, Fenaille F, Merda D, Blanco-Valle K, Feraudet-Tarisse C, Simon S, Hennekinne JA, Nia Y, Becher F. Top-Down Mass Spectrometry for Trace Level Quantification of Staphylococcal Enterotoxin A Variants. J Proteome Res 2021; 21:547-556. [PMID: 34968056 DOI: 10.1021/acs.jproteome.1c00886] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We addressed here the need for improved sensitivity of top-down mass spectrometry for identification, differentiation, and absolute quantification of sequence variants of SEA, a bacterial toxin produced by Staphylococcus aureus and regularly involved in food poisoning outbreaks (FPO). We combined immunoaffinity enrichment, a protein internal standard, and optimized acquisition conditions, either by full-scan high-resolution mass spectrometry (HRMS) or multiplex parallel reaction monitoring (PRM) mode. Deconvolution of full-scan HRMS signal and PRM detection of variant-specific fragment ions allowed confident identification of each SEA variant. Summing the PRM signal of variant-common fragment ions was most efficient for absolute quantification, illustrated by a sensitivity down to 2.5 ng/mL and an assay variability below 15%. Additionally, we showed that relative PRM fragment ion abundances constituted a supplementary specificity criterion in top-down quantification. The top-down method was successfully evaluated on a panel of enterotoxin-producing strains isolated during FPO, in parallel to the conventional whole genome sequencing, ELISA, and bottom-up mass spectrometry methods. Top-down provided at the same time correct identification of the SEA variants produced and precise determination of the toxin level. The raw files generated in this study can be found on PASSEL (Peptide Atlas) under data set identifier PASS01710.
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Affiliation(s)
- Donatien Lefebvre
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 91191 Gif-sur-Yvette, France.,Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France
| | - François Fenaille
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 91191 Gif-sur-Yvette, France
| | - Déborah Merda
- Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France
| | - Kevin Blanco-Valle
- Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France
| | - Cécile Feraudet-Tarisse
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 91191 Gif-sur-Yvette, France
| | - Stéphanie Simon
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 91191 Gif-sur-Yvette, France
| | - Jacques-Antoine Hennekinne
- Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France
| | - Yacine Nia
- Laboratory for Food Safety, French Agency for Food, Environmental and Occupational Health & Safety (ANSES), Université Paris-Est, 94700 Maisons-Alfort, France
| | - François Becher
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, 91191 Gif-sur-Yvette, France
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3
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Zhang Y, Tang Y, Tan C, Xu W. Toward Nanopore Electrospray Mass Spectrometry: Nanopore Effects in the Analysis of Bacteria. ACS CENTRAL SCIENCE 2020; 6:1001-1008. [PMID: 32607447 PMCID: PMC7318062 DOI: 10.1021/acscentsci.0c00622] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Indexed: 05/13/2023]
Abstract
The shape and structure analyses capability of nanopore is powerful and complementary to mass spectrometry analysis. It is extremely attractive but challenging to integrate these two techniques. The feasibility of combining nanopore electrospray with mass spectrometry was explored in this study. A nanopore effect was observed during the nano-electrospray of single bacterium, through which the shape and dimension of a single bacterium could be obtained. Molecular information on these bacteria was then acquired by analyzing these bacteria deposited on the counter electrode through laser spray ionization mass spectrometry experiments. Proof-of-concept experiments were carried out for four types of bacteria. Results show that the combination of nanopore results with mass spectrum data could effectively improve the identification accuracy of these bacteria from 72.5% to 100%. Although initial experiments were demonstrated in this work, results showed that it is feasible and promising to integrate nanopore technology with mass spectrometry for large biomolecule studies in the near future.
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Affiliation(s)
| | | | | | - Wei Xu
- . Web: http://www.escience.cn/people/weixu
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4
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Brodbelt JS, Morrison LJ, Santos I. Ultraviolet Photodissociation Mass Spectrometry for Analysis of Biological Molecules. Chem Rev 2020; 120:3328-3380. [PMID: 31851501 PMCID: PMC7145764 DOI: 10.1021/acs.chemrev.9b00440] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The development of new ion-activation/dissociation methods continues to be one of the most active areas of mass spectrometry owing to the broad applications of tandem mass spectrometry in the identification and structural characterization of molecules. This Review will showcase the impact of ultraviolet photodissociation (UVPD) as a frontier strategy for generating informative fragmentation patterns of ions, especially for biological molecules whose complicated structures, subtle modifications, and large sizes often impede molecular characterization. UVPD energizes ions via absorption of high-energy photons, which allows access to new dissociation pathways relative to more conventional ion-activation methods. Applications of UVPD for the analysis of peptides, proteins, lipids, and other classes of biologically relevant molecules are emphasized in this Review.
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Affiliation(s)
- Jennifer S. Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Lindsay J. Morrison
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Inês Santos
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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5
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Peters-Clarke TM, Quan Q, Brademan DR, Hebert AS, Westphall MS, Coon JJ. Ribonucleic Acid Sequence Characterization by Negative Electron Transfer Dissociation Mass Spectrometry. Anal Chem 2020; 92:4436-4444. [PMID: 32091202 PMCID: PMC7161943 DOI: 10.1021/acs.analchem.9b05388] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Modified oligonucleotides represent a promising avenue for drug development, with small interfering RNAs (siRNA) and microRNAs gaining traction in the therapeutic market. Mass spectrometry (MS)-based analysis offers many benefits for characterizing modified nucleic acids. Negative electron transfer dissociation (NETD) has proven valuable in sequencing oligonucleotide anions, particularly because it can retain modifications while generating sequence-informative fragments. We show that NETD can be successfully implemented on a widely available quadrupole-Orbitrap-linear ion trap mass spectrometer that uses a front-end glow discharge source to generate radical fluoranthene reagent cations. We characterize both unmodified and modified ribonucleic acids and present the first application of activated-ion negative electron transfer dissociation (AI-NETD) to nucleic acids. AI-NETD achieved 100% sequence coverage for both a 6-mer (5'-rGmUrArCmUrG-3') with 2'-O-methyl modifications and a 21-mer (5'-rCrArUrCrCrUrCrUrArGrArGrGrArUrArGrArArUrG-3'), the luciferase antisense siRNA. Both NETD and AI-NETD afforded complete sequence coverage of these molecules while maintaining a relatively low degree of undesired base-loss products and internal products relative to collision-based methods.
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Affiliation(s)
| | - Qiuwen Quan
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Dain R. Brademan
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | | | | | - Joshua J. Coon
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
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6
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Greer SM, Bern M, Becker C, Brodbelt JS. Extending Proteome Coverage by Combining MS/MS Methods and a Modified Bioinformatics Platform Adapted for Database Searching of Positive and Negative Polarity 193 nm Ultraviolet Photodissociation Mass Spectra. J Proteome Res 2018; 17:1340-1347. [DOI: 10.1021/acs.jproteome.7b00673] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Sylvester M. Greer
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Marshall Bern
- Protein
Metrics,
Inc., San Carlos, California 94070, United States
| | | | - Jennifer S. Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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7
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Affiliation(s)
- Nicholas
M. Riley
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Genome
Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Joshua J. Coon
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Genome
Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department
of Biomolecular Chemistry, University of
Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Morgridge
Institute for Research, Madison, Wisconsin 53715, United States
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8
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Rush MJP, Riley NM, Westphall MS, Syka JEP, Coon JJ. Sulfur Pentafluoride is a Preferred Reagent Cation for Negative Electron Transfer Dissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1324-1332. [PMID: 28349437 PMCID: PMC5483201 DOI: 10.1007/s13361-017-1600-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 05/10/2023]
Abstract
Negative mode proteome analysis offers access to unique portions of the proteome and several acidic post-translational modifications; however, traditional collision-based fragmentation methods fail to reliably provide sequence information for peptide anions. Negative electron transfer dissociation (NETD), on the other hand, can sequence precursor anions in a high-throughput manner. Similar to other ion-ion methods, NETD is most efficient with peptides of higher charge state because of the increased electrostatic interaction between reacting molecules. Here we demonstrate that NETD performance for lower charge state precursors can be improved by altering the reagent cation. Specifically, the recombination energy of the NETD reaction-largely dictated by the ionization energy (IE) of the reagent cation-can affect the extent of fragmentation. We compare the NETD reagent cations of C16H10●+ (IE = 7.9 eV) and SF5●+ (IE = 9.6 eV) on a set of standard peptides, concluding that SF5●+ yields greater sequence ion generation. Subsequent proteome-scale nLC-MS/MS experiments comparing C16H10●+ and SF5●+ further supported this outcome: analyses using SF5●+ yielded 4637 peptide spectral matches (PSMs) and 2900 unique peptides, whereas C16H10●+ produced 3563 PSMs and 2231 peptides. The substantive gain in identification power with SF5●+ was largely driven by improved identification of doubly deprotonated precursors, indicating that increased NETD recombination energy can increase product ion yield for low charge density precursors. This work demonstrates that SF5●+ is a viable, if not favorable, reagent cation for NETD, and provides improved fragmentation over the commonly used fluoranthene reagent. Graphical Abstract ᅟ.
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Affiliation(s)
- Matthew J P Rush
- Department of Chemistry, University of Wisconsin, Madison, WI, 53706, USA
- Department of Genome Center, University of Wisconsin, Madison, WI, 53706, USA
| | - Nicholas M Riley
- Department of Chemistry, University of Wisconsin, Madison, WI, 53706, USA
- Department of Genome Center, University of Wisconsin, Madison, WI, 53706, USA
| | - Michael S Westphall
- Department of Genome Center, University of Wisconsin, Madison, WI, 53706, USA
| | | | - Joshua J Coon
- Department of Chemistry, University of Wisconsin, Madison, WI, 53706, USA.
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI, 53706, USA.
- Department of Genome Center, University of Wisconsin, Madison, WI, 53706, USA.
- Mordgridge Institute for Research, Madison, WI, 53705, USA.
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9
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Riley NM, Hebert AS, Dürnberger G, Stanek F, Mechtler K, Westphall MS, Coon JJ. Phosphoproteomics with Activated Ion Electron Transfer Dissociation. Anal Chem 2017; 89:6367-6376. [PMID: 28383256 PMCID: PMC5555596 DOI: 10.1021/acs.analchem.7b00212] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability to localize phosphosites to specific amino acid residues is crucial to translating phosphoproteomic data into biological meaningful contexts. In a companion manuscript ( Anal. Chem. 2017 , DOI: 10.1021/acs.analchem.7b00213 ), we described a new implementation of activated ion electron transfer dissociation (AI-ETD) on a quadrupole-Orbitrap-linear ion trap hybrid MS system (Orbitrap Fusion Lumos), which greatly improved peptide fragmentation and identification over ETD and other supplemental activation methods. Here we present the performance of AI-ETD for identifying and localizing sites of phosphorylation in both phosphopeptides and intact phosphoproteins. Using 90 min analyses we show that AI-ETD can identify 24,503 localized phosphopeptide spectral matches enriched from mouse brain lysates, which more than triples identifications from standard ETD experiments and outperforms ETcaD and EThcD as well. AI-ETD achieves these gains through improved quality of fragmentation and MS/MS success rates for all precursor charge states, especially for doubly protonated species. We also evaluate the degree to which phosphate neutral loss occurs from phosphopeptide product ions due to the infrared photoactivation of AI-ETD and show that modifying phosphoRS (a phosphosite localization algorithm) to include phosphate neutral losses can significantly improve localization in AI-ETD spectra. Finally, we demonstrate the utility of AI-ETD in localizing phosphosites in α-casein, an ∼23.5 kDa phosphoprotein that showed eight of nine known phosphorylation sites occupied upon intact mass analysis. AI-ETD provided the greatest sequence coverage for all five charge states investigated and was the only fragmentation method to localize all eight phosphosites for each precursor. Overall, this work highlights the analytical value AI-ETD can bring to both bottom-up and top-down phosphoproteomics.
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Affiliation(s)
- Nicholas M. Riley
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Alexander S. Hebert
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Gerhard Dürnberger
- Institute of Molecular Pathology (IMP), Campus-Vienna-Biocenter 1, A-1030 Vienna, Austria
- GMI, Gregor Mendel Institute of Molecular Plant Biology, Dr. Bohr Gasse 3, A-1030 Vienna, Austria
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr Gasse 3, A-1030 Vienna, Austria
| | - Florian Stanek
- Institute of Molecular Pathology (IMP), Campus-Vienna-Biocenter 1, A-1030 Vienna, Austria
| | - Karl Mechtler
- Institute of Molecular Pathology (IMP), Campus-Vienna-Biocenter 1, A-1030 Vienna, Austria
- IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr Gasse 3, A-1030 Vienna, Austria
| | - Michael S. Westphall
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Joshua J. Coon
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA
- Morgridge Institute for Research, Madison, Wisconsin, USA
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10
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Cleland TP, DeHart CJ, Fellers RT, VanNispen AJ, Greer JB, LeDuc RD, Parker WR, Thomas PM, Kelleher NL, Brodbelt JS. High-Throughput Analysis of Intact Human Proteins Using UVPD and HCD on an Orbitrap Mass Spectrometer. J Proteome Res 2017; 16:2072-2079. [PMID: 28412815 DOI: 10.1021/acs.jproteome.7b00043] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The analysis of intact proteins (top-down strategy) by mass spectrometry has great potential to elucidate proteoform variation, including patterns of post-translational modifications (PTMs), which may not be discernible by analysis of peptides alone (bottom-up approach). To maximize sequence coverage and localization of PTMs, various fragmentation modes have been developed to produce fragment ions from deep within intact proteins. Ultraviolet photodissociation (UVPD) has recently been shown to produce high sequence coverage and PTM retention on a variety of proteins, with increasing evidence of efficacy on a chromatographic time scale. However, utilization of UVPD for high-throughput top-down analysis to date has been limited by bioinformatics. Here we detected 153 proteins and 489 proteoforms using UVPD and 271 proteins and 982 proteoforms using higher energy collisional dissociation (HCD) in a comparative analysis of HeLa whole-cell lysate by qualitative top-down proteomics. Of the total detected proteoforms, 286 overlapped between the UVPD and HCD data sets, with 68% of proteoforms having C scores greater than 40 for UVPD and 63% for HCD. The average sequence coverage (28 ± 20% for UVPD versus 17 ± 8% for HCD, p < 0.0001) was found to be higher for UVPD than HCD and with a trend toward improvement in q value for the UVPD data set. This study demonstrates the complementarity of UVPD and HCD for more extensive protein profiling and proteoform characterization.
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Affiliation(s)
- Timothy P Cleland
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Caroline J DeHart
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States
| | - Ryan T Fellers
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States
| | - Alexandra J VanNispen
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States
| | - Joseph B Greer
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States
| | - Richard D LeDuc
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States
| | - W Ryan Parker
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
| | - Paul M Thomas
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States.,Departments of Chemistry, Molecular Biosciences, and the Feinberg School of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Neil L Kelleher
- National Resource for Translational and Developmental Proteomics, Northwestern University , Evanston, Illinois 60208, United States.,Departments of Chemistry, Molecular Biosciences, and the Feinberg School of Medicine, Northwestern University , Evanston, Illinois 60208, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
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11
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Mayfield JE, Robinson MR, Cotham VC, Irani S, Matthews WL, Ram A, Gilmour DS, Cannon JR, Zhang YJ, Brodbelt JS. Mapping the Phosphorylation Pattern of Drosophila melanogaster RNA Polymerase II Carboxyl-Terminal Domain Using Ultraviolet Photodissociation Mass Spectrometry. ACS Chem Biol 2017; 12:153-162. [PMID: 28103682 DOI: 10.1021/acschembio.6b00729] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Phosphorylation of the C-terminal domain of RNA polymerase II (CTD) plays an essential role in eukaryotic transcription by recruiting transcriptional regulatory factors to the active polymerase. However, the scarcity of basic residues and repetitive nature of the CTD sequence impose a huge challenge for site-specific characterization of phosphorylation, hindering our understanding of this crucial biological process. Herein, we apply LC-UVPD-MS methods to analyze post-translational modification along native sequence CTDs. Application of our method to the Drosophila melanogaster CTD reveals the phosphorylation pattern of this model organism for the first time. The divergent nature of fly CTD allows us to derive rules defining how flanking residues affect phosphorylation choice by CTD kinases. Our data support the use of LC-UVPD-MS to decipher the CTD code and determine rules that program its function.
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Affiliation(s)
| | | | | | | | | | | | - David S. Gilmour
- Department
of Biochemistry and Molecular Biology, Penn State University, University Park, Pennsylvania 16802, United States
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12
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Cleland TP, Thomas CJ, Gundberg CM, Vashishth D. Influence of carboxylation on osteocalcin detection by mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:2109-15. [PMID: 27470908 PMCID: PMC5014568 DOI: 10.1002/rcm.7692] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 07/15/2016] [Accepted: 07/15/2016] [Indexed: 06/06/2023]
Abstract
RATIONALE Osteocalcin is a small, abundant bone protein that is difficult to detect using high-throughput tandem mass spectrometry (MS/MS) proteomic approaches from bone protein extracts, and is predominantly detected by non-MS immunological methods. Here, we analyze bovine osteocalcin and its post-translational modifications to determine why a protein of this size goes undetected. METHODS Osteocalcin was purified from cow bone using well-established methods. Intact osteocalcin or trypsin-digested osteocalcin were separated using an Agilent 1200 series high-performance liquid chromatography (HPLC) system and analyzed using a ThermoScientific LTQ-Orbitrap XL after fragmentation with higher-energy collision dissociation. Data were analyzed using Mascot or Prosight Lite. RESULTS Our results support previous findings that the cow osteocalcin has up to three carboxylations using both intact osteocalcin and digested forms. Using Mascot, we were able to detect osteocalcin peptides, but no fragments that localized the carboxylations. Full annotation using Prosight Lite of the intact (three carboxylations), N-terminal peptide (one carboxylation), and middle peptide (two carboxylations) showed complete fragmentation was present, but complete neutral loss was observed. CONCLUSIONS Osteocalcin carboxylation, and its associated neutral losses, makes high-throughput detection of this protein challenging; however, alternative fragmentation or limited purification can overcome these challenges. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Timothy P Cleland
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12182, USA
| | - Corinne J Thomas
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12182, USA
| | - Caren M Gundberg
- Department of Orthopedics and Rehabilitation, Yale University, New Haven, CT, 06520, USA
| | - Deepak Vashishth
- Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12182, USA.
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13
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Robinson MR, Taliaferro JM, Dalby KN, Brodbelt JS. 193 nm Ultraviolet Photodissociation Mass Spectrometry for Phosphopeptide Characterization in the Positive and Negative Ion Modes. J Proteome Res 2016; 15:2739-48. [PMID: 27425180 DOI: 10.1021/acs.jproteome.6b00289] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Advances in liquid chromatography tandem mass spectrometry (LC-MS/MS) have permitted phosphoproteomic analysis on a grand scale, but ongoing challenges specifically associated with confident phosphate localization continue to motivate the development of new fragmentation techniques. In the present study, ultraviolet photodissociation (UVPD) at 193 nm is evaluated for the characterization of phosphopeptides in both positive and negative ion modes. Compared to the more standard higher energy collisional dissociation (HCD), UVPD provided more extensive fragmentation with improved phosphate retention on product ions. Negative mode UVPD showed particular merit for detecting and sequencing highly acidic phosphopeptides from alpha and beta casein, but was not as robust for larger scale analysis because of lower ionization efficiencies in the negative mode. HeLa and HCC70 cell lysates were analyzed by both UVPD and HCD. While HCD identified more phosphopeptides and proteins compared to UVPD, the unique matches from UVPD analysis could be combined with the HCD data set to improve the overall depth of coverage compared to either method alone.
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Affiliation(s)
- Michelle R Robinson
- Department of Chemistry, and ‡Division of Chemical Biology and Medicinal Chemistry College of Pharmacy, The University of Texas Austin, Texas 78712, United States
| | - Juliana M Taliaferro
- Department of Chemistry, and ‡Division of Chemical Biology and Medicinal Chemistry College of Pharmacy, The University of Texas Austin, Texas 78712, United States
| | - Kevin N Dalby
- Department of Chemistry, and ‡Division of Chemical Biology and Medicinal Chemistry College of Pharmacy, The University of Texas Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, and ‡Division of Chemical Biology and Medicinal Chemistry College of Pharmacy, The University of Texas Austin, Texas 78712, United States
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14
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Riley NM, Bern M, Westphall MS, Coon JJ. Full-Featured Search Algorithm for Negative Electron-Transfer Dissociation. J Proteome Res 2016; 15:2768-76. [PMID: 27402189 DOI: 10.1021/acs.jproteome.6b00319] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Negative electron-transfer dissociation (NETD) has emerged as a premier tool for peptide anion analysis, offering access to acidic post-translational modifications and regions of the proteome that are intractable with traditional positive-mode approaches. Whole-proteome scale characterization is now possible with NETD, but proper informatic tools are needed to capitalize on advances in instrumentation. Currently only one database search algorithm (OMSSA) can process NETD data. Here we implement NETD search capabilities into the Byonic platform to improve the sensitivity of negative-mode data analyses, and we benchmark these improvements using 90 min LC-MS/MS analyses of tryptic peptides from human embryonic stem cells. With this new algorithm for searching NETD data, we improved the number of successfully identified spectra by as much as 80% and identified 8665 unique peptides, 24 639 peptide spectral matches, and 1338 proteins in activated-ion NETD analyses, more than doubling identifications from previous negative-mode characterizations of the human proteome. Furthermore, we reanalyzed our recently published large-scale, multienzyme negative-mode yeast proteome data, improving peptide and peptide spectral match identifications and considerably increasing protein sequence coverage. In all, we show that new informatics tools, in combination with recent advances in data acquisition, can significantly improve proteome characterization in negative-mode approaches.
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Affiliation(s)
- Nicholas M Riley
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Genome Center of Wisconsin, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Marshall Bern
- Protein Metrics, Inc. , San Carlos, California 94070, United States
| | - Michael S Westphall
- Genome Center of Wisconsin, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Joshua J Coon
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Genome Center of Wisconsin, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.,Department of Biomolecular Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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15
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Halim MA, Girod M, MacAleese L, Lemoine J, Antoine R, Dugourd P. 213 nm Ultraviolet Photodissociation on Peptide Anions: Radical-Directed Fragmentation Patterns. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:474-86. [PMID: 26545767 DOI: 10.1007/s13361-015-1297-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 10/13/2015] [Accepted: 10/16/2015] [Indexed: 05/25/2023]
Abstract
Characterization of acidic peptides and proteins is greatly hindered due to lack of suitable analytical techniques. Here we present the implementation of 213 nm ultraviolet photodissociation (UVPD) in high-resolution quadrupole-Orbitrap mass spectrometer in negative polarity for peptide anions. Radical-driven backbone fragmentation provides 22 distinctive fragment ion types, achieving the complete sequence coverage for all reported peptides. Hydrogen-deficient radical anion not only promotes the cleavage of Cα-C bond but also stimulates the breaking of N-Cα and C-N bonds. Radical-directed loss of small molecules and specific side chain of amino acids are detected in these experiments. Radical containing side chain of amino acids (Tyr, Ser, Thr, and Asp) may possibly support the N-Cα backbone fragmentation. Proline comprising peptides exhibit the unusual fragment ions similar to reported earlier. Interestingly, basic amino acids such as Arg and Lys also stimulated the formation of abundant b and y ions of the related peptide anions. Loss of hydrogen atom from the charge-reduced radical anion and fragment ions are rationalized by time-dependent density functional theory (TDDFT) calculation, locating the potential energy surface (PES) of ππ* and repulsive πσ* excited states of a model amide system.
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Affiliation(s)
- Mohammad A Halim
- Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France
| | - Marion Girod
- Institut des Sciences Analytiques, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France
| | - Luke MacAleese
- Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France
| | - Jérôme Lemoine
- Institut des Sciences Analytiques, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France
| | - Rodolphe Antoine
- Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France
| | - Philippe Dugourd
- Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
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16
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Affiliation(s)
- Nicholas M. Riley
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Joshua J. Coon
- Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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17
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Affiliation(s)
- Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin , Austin, Texas 78712, United States
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18
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Iftikhar I, Brajter-Toth A. Solution or Gas Phase? Oxidation and Radical Formation in Electrospray Ionization Mass Spectrometry (ESI MS). ELECTROANAL 2015. [DOI: 10.1002/elan.201500297] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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19
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Riley NM, Rush MJP, Rose CM, Richards AL, Kwiecien NW, Bailey DJ, Hebert AS, Westphall MS, Coon JJ. The Negative Mode Proteome with Activated Ion Negative Electron Transfer Dissociation (AI-NETD). Mol Cell Proteomics 2015; 14:2644-60. [PMID: 26193884 DOI: 10.1074/mcp.m115.049726] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Indexed: 01/15/2023] Open
Abstract
The field of proteomics almost uniformly relies on peptide cation analysis, leading to an underrepresentation of acidic portions of proteomes, including relevant acidic posttranslational modifications. Despite the many benefits negative mode proteomics can offer, peptide anion analysis remains in its infancy due mainly to challenges with high-pH reversed-phase separations and a lack of robust fragmentation methods suitable for peptide anion characterization. Here, we report the first implementation of activated ion negative electron transfer dissociation (AI-NETD) on the chromatographic timescale, generating 7,601 unique peptide identifications from Saccharomyces cerevisiae in single-shot nLC-MS/MS analyses of tryptic peptides-a greater than 5-fold increase over previous results with NETD alone. These improvements translate to identification of 1,106 proteins, making this work the first negative mode study to identify more than 1,000 proteins in any system. We then compare the performance of AI-NETD for analysis of peptides generated by five proteases (trypsin, LysC, GluC, chymotrypsin, and AspN) for negative mode analyses, identifying as many as 5,356 peptides (1,045 proteins) with LysC and 4,213 peptides (857 proteins) with GluC in yeast-characterizing 1,359 proteins in total. Finally, we present the first deep-sequencing approach for negative mode proteomics, leveraging offline low-pH reversed-phase fractionation prior to online high-pH separations and peptide fragmentation with AI-NETD. With this platform, we identified 3,467 proteins in yeast with trypsin alone and characterized a total of 3,730 proteins using multiple proteases, or nearly 83% of the expressed yeast proteome. This work represents the most extensive negative mode proteomics study to date, establishing AI-NETD as a robust tool for large-scale peptide anion characterization and making the negative mode approach a more viable platform for future proteomic studies.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Joshua J Coon
- From the ‡Department of Chemistry, §Genome Center, and ¶Department of Biomolecular Chemistry University of Wisconsin, Madison, Wisconsin, 53706
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Greer S, Cannon JR, Brodbelt JS. Improvement of shotgun proteomics in the negative mode by carbamylation of peptides and ultraviolet photodissociation mass spectrometry. Anal Chem 2014; 86:12285-90. [PMID: 25420043 PMCID: PMC4270407 DOI: 10.1021/ac5035314] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2014] [Accepted: 11/24/2014] [Indexed: 02/08/2023]
Abstract
Although acidic peptides compose a substantial portion of many proteomes, their less efficient ionization during positive polarity electrospray ionization (ESI) impedes their detection in bottom-up mass spectrometry workflows. We have implemented a derivatization strategy based on carbamylation which converts basic amine sites (Lys, N-termini) to less basic amides for enhanced analysis in the negative mode. Ultraviolet photodissociation (UVPD) is used to analyze the resulting peptide anions, as demonstrated for tryptic peptides from bovine serum albumin and Halobacterium salinarum in a high throughput liquid chromatography/tandem mass spectrometry (LC/MS/MS) mode. LC/UVPD-MS of a carbamylated H. salinarum digest resulted in 45% more identified peptides and 25% more proteins compared to the unmodified digest analyzed in the negative mode.
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Affiliation(s)
- Sylvester
M. Greer
- Department of Chemistry, University of
Texas at Austin, Austin, Texas 78712, United
States
| | - Joe R. Cannon
- Department of Chemistry, University of
Texas at Austin, Austin, Texas 78712, United
States
| | - Jennifer S. Brodbelt
- Department of Chemistry, University of
Texas at Austin, Austin, Texas 78712, United
States
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21
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Robinson MR, Moore KL, Brodbelt JS. Direct identification of tyrosine sulfation by using ultraviolet photodissociation mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1461-71. [PMID: 24845354 PMCID: PMC4108549 DOI: 10.1007/s13361-014-0910-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Revised: 03/30/2014] [Accepted: 04/05/2014] [Indexed: 05/25/2023]
Abstract
Sulfation is a common post-translational modification of tyrosine residues in eukaryotes; however, detection using traditional liquid chromatography-mass spectrometry (LC-MS) methods is challenging based on poor ionization efficiency in the positive ion mode and facile neutral loss upon collisional activation. In the present study, 193 nm ultraviolet photodissociation (UVPD) is applied to sulfopeptide anions to generate diagnostic sequence ions, which do not undergo appreciable neutral loss of sulfate even using higher energy photoirradiation parameters. At the same time, neutral loss of SO₃ is observed from the precursor and charge-reduced precursor ions, a spectral feature that is useful for differentiating tyrosine sulfation from the nominally isobaric tyrosine phosphorylation. LC-MS detection limits for UVPD analysis in the negative mode were determined to be around 100 fmol for three sulfated peptides, caerulein, cionin, and leu-enkephalin. The LC-UVPD-MS method was applied for analysis of bovine fibrinogen, and its key sulfated peptide was confidently identified.
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Affiliation(s)
- Michelle R Robinson
- Department of Chemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX, 78712, USA
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22
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Brodbelt JS. Photodissociation mass spectrometry: new tools for characterization of biological molecules. Chem Soc Rev 2014; 43:2757-83. [PMID: 24481009 PMCID: PMC3966968 DOI: 10.1039/c3cs60444f] [Citation(s) in RCA: 232] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Photodissociation mass spectrometry combines the ability to activate and fragment ions using photons with the sensitive detection of the resulting product ions by mass spectrometry. This combination affords a versatile tool for characterization of biological molecules. The scope and breadth of photodissociation mass spectrometry have increased substantially over the past decade as new research groups have entered the field and developed a number of innovative applications that illustrate the ability of photodissociation to produce rich fragmentation patterns, to cleave bonds selectively, and to target specific molecules based on incorporation of chromophores. This review focuses on many of the key developments in photodissociation mass spectrometry over the past decade with a particular emphasis on its applications to biological molecules.
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23
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Mathieson JS, Cooper GJT, Symes MD, Cronin L. Quantification of ion binding using electrospray mass spectrometry. Inorg Chem Front 2014. [DOI: 10.1039/c3qi00037k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Smith SA, Kalcic CL, Cui L, Reid GE. Femtosecond laser-induced ionization/dissociation tandem mass spectrometry (fsLID-MS/MS) of deprotonated phosphopeptide anions. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:2807-2817. [PMID: 24214867 DOI: 10.1002/rcm.6750] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 09/24/2013] [Accepted: 09/25/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Radical-directed dissociation techniques provide structural information which is complementary to that from conventional collision-induced dissociation (CID). The analysis of phosphopeptide anions is warranted due to their relatively acidic character. As femtosecond laser-induced ionization/dissociation tandem mass spectrometry (fsLID-MS/MS) is uniquely initiated by field ionization, an investigation is warranted to determine whether fsLID may provide novel analytical utility for phosphopeptide anions. METHODS Twenty-three synthetic deprotonated phosphopeptide anions were introduced into a three-dimensional quadrupole ion trap mass spectrometer via electrospray ionization. The ion trap was interfaced with a near-IR (802 nm) ultrashort-pulsed (35 fs FWHM) ultrahigh-powered (peak power ~10(14) W/cm(2)) laser system. Performance comparisons are made with other techniques applied to phosphopeptide anion analysis, including CID, electron detachment dissociation (EDD), negative electron transfer dissociation (NETD), activated electron photodetachment dissociation (activated-EPD), and ultraviolet photodissociation (UVPD). RESULTS FsLID-MS/MS of multiply deprotonated phosphopeptide anions provides sequence information via phosphorylation-intact a/x ions in addition to other sequence ions, satellite ions, and side-chain losses. Novel fragmentation processes include selective c-ion formation N-terminal to Ser/Thr and a phosphorylation-specific correlation between xn -98 ion abundances and phosphorylation at the n(th) residue. Sequencing-quality data required about 30 s of signal averaging. fsLID-MS/MS of singly deprotonated phosphopeptides did not yield product anions with stable trajectories, despite significant depletion of the precursor. CONCLUSIONS Multiply deprotonated phosphopeptide anions were sequenced via negative-mode fsLID-MS/MS, with phosphosite localization facilitated by a/x ion series in addition to diagnostic x(n)-98 ions. fsLID-MS/MS is qualitatively competitive with other techniques. Further efficiency enhancements (e.g., implementation on a linear trap or/and higher pulse frequencies) may permit sequence analyses on chromatographic timescales.
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Affiliation(s)
- Scott A Smith
- RTSF Mass Spectrometry & Metabolomics Core, Michigan State University, East Lansing, MI, 48824, USA
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25
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O'Brien JP, Brodbelt JS. Structural characterization of gangliosides and glycolipids via ultraviolet photodissociation mass spectrometry. Anal Chem 2013; 85:10399-407. [PMID: 24083420 DOI: 10.1021/ac402379y] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ultraviolet photodissociation (UVPD) mass spectrometry was used to characterize the structures of amphiphilic glycosphingolipids and gangliosides in comparison to collision induced dissociation (CID) and higher energy collision dissociation (HCD) in a high performance Orbitrap mass spectrometer. UVPD produced the widest array of fragment ions diagnostic for both the ceramide base and oligosaccharide moieties. CID and HCD generated mainly glycosidic B/Y and C/Z cleavages of the oligosaccharides moieties and very few informative fragments related to the hydrophobic ceramide base. Several unique cleavages at the sphingoid base and the fatty acid chain occurred upon UVPD, as well as a wider variety of cross ring cleavages (A/X ions), thus affording differentiation of isobaric gangliosides. An LC-UVPD-MS strategy allowed the elucidation of 27 gangliosides among five different classes.
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Affiliation(s)
- John P O'Brien
- Department of Chemistry, The University of Texas at Austin , 1 University Station A5300, Austin, Texas, United States 78712
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Robotham SA, Kluwe C, Cannon JR, Ellington A, Brodbelt JS. De novo sequencing of peptides using selective 351 nm ultraviolet photodissociation mass spectrometry. Anal Chem 2013; 85:9832-8. [PMID: 24050806 DOI: 10.1021/ac402309h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Although in silico database search methods remain more popular for shotgun proteomics methods, de novo sequencing offers the ability to identify peptides derived from proteins lacking sequenced genomes and ones with subtle splice variants or truncations. Ultraviolet photodissociation (UVPD) of peptides derivatized by selective attachment of a chromophore at the N-terminus generates a characteristic series of y ions. The UVPD spectra of the chromophore-labeled peptides are simplified and thus amenable to de novo sequencing. This method resulted in an observed sequence coverage of 79% for cytochrome C (eight peptides), 47% for β-lactoglobulin (five peptides), 25% for carbonic anhydrase (six peptides), and 51% for bovine serum albumin (33 peptides). This strategy also allowed differentiation of proteins with high sequence homology as evidenced by de novo sequencing of two variants of green fluorescent protein.
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Affiliation(s)
- Scott A Robotham
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
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Abstract
American Society for Mass Spectrometry Sanibel meeting on top-down mass spectrometry St Pete Beach, FL, USA, 24-27 January 2013 Top-down mass spectrometry involves analysis of intact proteins, typically using electrospray ionization, as multiple charging enhances dissociation and thus identification by comparison of precursor and product ion masses with protein sequence databases. Traditionally a low-throughput, precision technology performed on high-resolution Fourier-transform ion cyclotron resonance mass analyzers, top-down proteomics aims to increase throughput for whole proteome analysis while preserving the inherent value of an intact protein mass measurement. This years' American Society for Mass Spectrometry Sanibel meeting brought together established scientists who have demonstrated the viability of the top-down approach and its applicability to virtually all segments of the proteome, mixing them with researchers from diverse areas and with the common interest of advancing top-down into the high-throughput proteomics mainstream. Advances in instrumentation including the orbitrap analyzer, ionization mechanisms, dissociation strategies and informatics, as well as a wide variety of applications, were discussed in depth, leading to the inescapable conclusion that the future for top-down is bright.
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Affiliation(s)
- Julian Whitelegge
- The Pasarow Mass Spectrometry Laboratory, UCLA, Jane and Terry Semel Institute for Neuroscience and Human Behavior, Los Angeles, CA 90095, USA.
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