1
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Penanes P, Gorshkov V, Ivanov MV, Gorshkov MV, Kjeldsen F. Potential of Negative-Ion-Mode Proteomics: An MS1-Only Approach. J Proteome Res 2023; 22:2734-2742. [PMID: 37395192 PMCID: PMC10407931 DOI: 10.1021/acs.jproteome.3c00307] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Indexed: 07/04/2023]
Abstract
Current proteomics approaches rely almost exclusively on using the positive ionization mode, resulting in inefficient ionization of many acidic peptides. This study investigates protein identification efficiency in the negative ionization mode using the DirectMS1 method. DirectMS1 is an ultrafast data acquisition method based on accurate peptide mass measurements and predicted retention times. Our method achieves the highest rate of protein identification in the negative ion mode to date, identifying over 1000 proteins in a human cell line at a 1% false discovery rate. This is accomplished using a single-shot 10 min separation gradient, comparable to lengthy MS/MS-based analyses. Optimizing separation and experimental conditions was achieved by utilizing mobile buffers containing 2.5 mM imidazole and 3% isopropanol. The study emphasized the complementary nature of data obtained in positive and negative ion modes. Combining the results from all replicates in both polarities increased the number of identified proteins to 1774. Additionally, we analyzed the method's efficiency using different proteases for protein digestion. Among the four studied proteases (LysC, GluC, AspN, and trypsin), trypsin and LysC demonstrated the highest protein identification yield. This suggests that digestion procedures utilized in positive-mode proteomics can be effectively applied in the negative ion mode. Data are deposited to ProteomeXchange: PXD040583.
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Affiliation(s)
- Pelayo
A. Penanes
- Department
of Biochemistry and Molecular Biology, University
of Southern Denmark, DK-5230 Odense M, Denmark
| | - Vladimir Gorshkov
- Department
of Biochemistry and Molecular Biology, University
of Southern Denmark, DK-5230 Odense M, Denmark
| | - Mark V. Ivanov
- V.
L. Talrose Institute for Energy Problems of Chemical Physics, N. N. Semenov Federal Research Center for Chemical
Physics, Russian Academy of Sciences, 38 Leninsky Pr., Bld. 2, Moscow 119334, Russia
| | - Mikhail V. Gorshkov
- V.
L. Talrose Institute for Energy Problems of Chemical Physics, N. N. Semenov Federal Research Center for Chemical
Physics, Russian Academy of Sciences, 38 Leninsky Pr., Bld. 2, Moscow 119334, Russia
| | - Frank Kjeldsen
- Department
of Biochemistry and Molecular Biology, University
of Southern Denmark, DK-5230 Odense M, Denmark
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2
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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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3
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LeBlanc BM, Moreno RY, Escobar EE, Venkat Ramani MK, Brodbelt JS, Zhang Y. What's all the phos about? Insights into the phosphorylation state of the RNA polymerase II C-terminal domain via mass spectrometry. RSC Chem Biol 2021; 2:1084-1095. [PMID: 34458825 PMCID: PMC8341212 DOI: 10.1039/d1cb00083g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 06/03/2021] [Indexed: 12/31/2022] Open
Abstract
RNA polymerase II (RNAP II) is one of the primary enzymes responsible for expressing protein-encoding genes and some small nuclear RNAs. The enigmatic carboxy-terminal domain (CTD) of RNAP II and its phosphorylation state are critically important in regulating transcription in vivo. Early methods of identifying phosphorylation on the CTD heptad were plagued by issues of low specificity and ambiguous signals. However, advancements in the field of mass spectrometry (MS) have presented the opportunity to gain new insights into well-studied processes as well as explore new frontiers in transcription. By using MS, residues which are modified within the CTD heptad and across repeats are now able to be pinpointed. Likewise, identification of kinase and phosphatase specificity towards residues of the CTD has reached a new level of accuracy. Now, MS is being used to investigate the crosstalk between modified residues of the CTD and may be a critical technique for understanding how phosphorylation plays a role in the new LLPS model of transcription. Herein, we discuss the development of various MS techniques and evaluate their capabilities. By highlighting the pros and cons of each technique, we aim to provide future investigators with a comprehensive overview of how MS can be used to investigate the complexities of RNAP-II mediated transcription.
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Affiliation(s)
- Blase M LeBlanc
- Department of Molecular Biosciences, University of Texas Austin USA
| | - R Yvette Moreno
- Department of Molecular Biosciences, University of Texas Austin USA
| | | | | | | | - Yan Zhang
- Department of Molecular Biosciences, University of Texas Austin USA
- Institute of Cellular and Molecular Biology, University of Texas Austin USA
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4
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Venkat Ramani MK, Yang W, Irani S, Zhang Y. Simplicity is the Ultimate Sophistication-Crosstalk of Post-translational Modifications on the RNA Polymerase II. J Mol Biol 2021; 433:166912. [PMID: 33676925 PMCID: PMC8184622 DOI: 10.1016/j.jmb.2021.166912] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/23/2021] [Accepted: 02/26/2021] [Indexed: 12/19/2022]
Abstract
The highly conserved C-terminal domain (CTD) of the largest subunit of RNA polymerase II comprises a consensus heptad (Y1S2P3T4S5P6S7) repeated multiple times. Despite the simplicity of its sequence, the essential CTD domain orchestrates eukaryotic transcription and co-transcriptional processes, including transcription initiation, elongation, and termination, and mRNA processing. These distinct facets of the transcription cycle rely on specific post-translational modifications (PTM) of the CTD, in which five out of the seven residues in the heptad repeat are subject to phosphorylation. A hypothesis termed the "CTD code" has been proposed in which these PTMs and their combinations generate a sophisticated landscape for spatiotemporal recruitment of transcription regulators to Pol II. In this review, we summarize the recent experimental evidence understanding the biological role of the CTD, implicating a context-dependent theme that significantly enhances the ability of accurate transcription by RNA polymerase II. Furthermore, feedback communication between the CTD and histone modifications coordinates chromatin states with RNA polymerase II-mediated transcription, ensuring the effective and accurate conversion of information into cellular responses.
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Affiliation(s)
| | - Wanjie Yang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, United States
| | - Seema Irani
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, United States
| | - Yan Zhang
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, United States; The Institute for Cellular and Molecular Biology. University of Texas at Austin, Austin, TX 78712, United States.
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5
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Majuta SN, DeBastiani A, Li P, Valentine SJ. Combining Field-Enabled Capillary Vibrating Sharp-Edge Spray Ionization with Microflow Liquid Chromatography and Mass Spectrometry to Enhance 'Omics Analyses. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:473-485. [PMID: 33417454 PMCID: PMC8132193 DOI: 10.1021/jasms.0c00376] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Field-enabled capillary vibrating sharp-edge spray ionization (cVSSI) has been combined with high-flow liquid chromatography (LC) and mass spectrometry (MS) to establish current ionization capabilities for metabolomics and proteomics investigations. Comparisons are made between experiments employing cVSSI and a heated electrospray ionization probe representing the state-of-the-art in microflow LC-MS methods for 'omics studies. For metabolomics standards, cVSSI is shown to provide an ionization enhancement by factors of 4 ± 2 for both negative and positive ion mode analyses. For chymotryptic peptides, cVSSI is shown to provide an ionization enhancement by factors of 5 ± 2 and 2 ± 1 for negative and positive ion mode analyses, respectively. Slightly broader high-performance liquid chromatography peaks are observed in the cVSSI datasets, and several studies suggest that this results from a slightly decreased post-split flow rate. This may result from partial obstruction of the pulled-tip emitter over time. Such a challenge can be remedied with the use of LC pumps that operate in the 10 to 100 μL·min-1 flow regime. At this early stage, the proof-of-principle studies already show ion signal advantages over state-of-the-art electrospray ionization (ESI) for a wide variety of analytes in both positive and negative ion mode. Overall, this represents a ∼20-50-fold improvement over the first demonstration of LC-MS analyses by voltage-free cVSSI. Separate comparisons of the ion abundances of compounds eluting under identical solvent conditions reveal ionization efficiency differences between cVSSI and ESI and may suggest varied contributions to ionization from different physicochemical properties of the compounds. Future investigations of parameters that could further increase ionization gains in negative and positive ion mode analyses with the use of cVSSI are briefly presented.
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Affiliation(s)
- Sandra N. Majuta
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown WV 26501
| | - Anthony DeBastiani
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown WV 26501
| | - Peng Li
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown WV 26501
| | - Stephen J. Valentine
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown WV 26501
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6
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Ferreira JA, Relvas-Santos M, Peixoto A, M N Silva A, Lara Santos L. Glycoproteogenomics: Setting the Course for Next-generation Cancer Neoantigen Discovery for Cancer Vaccines. GENOMICS, PROTEOMICS & BIOINFORMATICS 2021; 19:25-43. [PMID: 34118464 PMCID: PMC8498922 DOI: 10.1016/j.gpb.2021.03.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 01/25/2021] [Accepted: 03/01/2021] [Indexed: 12/24/2022]
Abstract
Molecular-assisted precision oncology gained tremendous ground with high-throughput next-generation sequencing (NGS), supported by robust bioinformatics. The quest for genomics-based cancer medicine set the foundations for improved patient stratification, while unveiling a wide array of neoantigens for immunotherapy. Upfront pre-clinical and clinical studies have successfully used tumor-specific peptides in vaccines with minimal off-target effects. However, the low mutational burden presented by many lesions challenges the generalization of these solutions, requiring the diversification of neoantigen sources. Oncoproteogenomics utilizing customized databases for protein annotation by mass spectrometry (MS) is a powerful tool toward this end. Expanding the concept toward exploring proteoforms originated from post-translational modifications (PTMs) will be decisive to improve molecular subtyping and provide potentially targetable functional nodes with increased cancer specificity. Walking through the path of systems biology, we highlight that alterations in protein glycosylation at the cell surface not only have functional impact on cancer progression and dissemination but also originate unique molecular fingerprints for targeted therapeutics. Moreover, we discuss the outstanding challenges required to accommodate glycoproteomics in oncoproteogenomics platforms. We envisage that such rationale may flag a rather neglected research field, generating novel paradigms for precision oncology and immunotherapy.
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Affiliation(s)
- José Alexandre Ferreira
- Experimental Pathology and Therapeutics Group, Portuguese Institute of Oncology, Porto 4200-072, Portugal; Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto 4050-313, Portugal; Porto Comprehensive Cancer Center (P.ccc), Porto 4200-072, Portugal.
| | - Marta Relvas-Santos
- Experimental Pathology and Therapeutics Group, Portuguese Institute of Oncology, Porto 4200-072, Portugal; Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto 4050-313, Portugal; REQUIMTE-LAQV, Department of Chemistry and Biochemistry, Faculty of Sciences of the University of Porto, Porto 4169-007, Portugal
| | - Andreia Peixoto
- Experimental Pathology and Therapeutics Group, Portuguese Institute of Oncology, Porto 4200-072, Portugal; Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto 4050-313, Portugal
| | - André M N Silva
- REQUIMTE-LAQV, Department of Chemistry and Biochemistry, Faculty of Sciences of the University of Porto, Porto 4169-007, Portugal
| | - Lúcio Lara Santos
- Experimental Pathology and Therapeutics Group, Portuguese Institute of Oncology, Porto 4200-072, Portugal; Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto 4050-313, Portugal; Porto Comprehensive Cancer Center (P.ccc), Porto 4200-072, Portugal
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7
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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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8
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Li C, Attanayake K, Valentine SJ, Li P. Facile Improvement of Negative Ion Mode Electrospray Ionization Using Capillary Vibrating Sharp-Edge Spray Ionization. Anal Chem 2020; 92:2492-2502. [PMID: 31940176 PMCID: PMC7318871 DOI: 10.1021/acs.analchem.9b03983] [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: 12/11/2022]
Abstract
Electrospray ionization (ESI) is often affected by corona discharge when spraying 100% aqueous solutions as the voltage that induces discharge can be well below the onset voltage of ESI. As a result, it is especially challenging to perform native mass spectrometry in negative ion mode where 100% aqueous solution is preferred. Here we report a simple instrumentation method to improve the performance of ESI in negative ion mode based on capillary vibrating sharp-edge spray ionization. By attaching a fused silica capillary emitter to a vibrating glass slide, improved signal quality is achieved for various analytes in aqueous solutions over applying ESI alone. Compared to commercial ESI sources using nebulization gas to reduce discharge, 10-100-fold enhancement in signal intensity and 3-10-fold improvement in S/N are achieved for various kinds of molecules including DNA, peptides, proteins, and oligosaccharides. Finally, the new method demonstrates utility for native mass spectrometry analysis of proteins and G-quadruplex DNA. The present method is expected to have great potential to be adopted by the scientific community because of its improved analytical performance, simplicity, and low cost.
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Affiliation(s)
- Chong Li
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
| | - Kushani Attanayake
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
| | - Stephen J. Valentine
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
| | - Peng Li
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, USA
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9
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Bashyal A, Sanders JD, Holden DD, Brodbelt JS. Top-Down Analysis of Proteins in Low Charge States. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:704-717. [PMID: 30796622 PMCID: PMC6447437 DOI: 10.1007/s13361-019-02146-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 01/30/2019] [Accepted: 01/30/2019] [Indexed: 05/08/2023]
Abstract
The impact of charging methods on the dissociation behavior of intact proteins in low charge states is investigated using HCD and 193 nm UVPD. Low charge states are produced for seven different proteins using the following four different methods: (1) proton transfer reactions of ions in high charge states generated from conventional denaturing solutions; (2) ESI of proteins in solutions of high ionic strength to enhance retention of folded native-like conformations; (3) ESI of proteins in high pH solutions to limit protonation; and (4) ESI of carbamylated proteins. Comparison of sequence coverages, degree of preferential cleavages, and types and distribution of fragment ions reveals a number of differences in the fragmentation patterns depending on the method used to generate the ions. More notable differences in these metrics are observed upon HCD than upon UVPD. The fragmentation caused by HCD is influenced more significantly by the presence/absence of mobile protons, a factor that modulates the degree of preferential cleavages and net sequence coverages. Carbamylation of the lysines and the N-terminus of the proteins alters the proton mobility by reducing the number of proton-sequestering, highly basic sites as evidenced by decreased preferential fragmentation C-terminal to Asp or N-terminal to Pro upon HCD. UVPD is less dependent on the method used to generate the low charge states and favors non-specific fragmentation, an outcome which is important for obtaining high sequence coverage of intact proteins.
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Affiliation(s)
- Aarti Bashyal
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - James D Sanders
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Dustin D Holden
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Jennifer S Brodbelt
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA.
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10
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Guo C, Guo X, Zhao L, Chen D, Wang J, Sun J. Optimization of carbamylation conditions and study on the effects on the product ions of carbamylation and dual modification of the peptide by Q-TOF MS. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2018; 24:384-396. [PMID: 30041545 DOI: 10.1177/1469066718788665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Modified peptides fragmented by collision-induced dissociation can offer additional sequence information, which is beneficial for the de novo sequencing of peptides. Here, the model peptide VQGESNDLK was carbamylated. The optimal conditions were as follows: temperature of 90℃, pH of 7, and the time of 60 min. Then, we studied the b- and y-series ions of the native, carbamylated, and dual-modified peptides. The results were as follows. The short carbamylated peptides (≤10 amino acid residues) produced more b-series ions (including b1 ion). The long carbamylated peptides (>10 amino acid residues) produced additional b1 ion but fewer y-series ions (especially in the high-mass region). The short dual-modified peptides produced more b-series ions (including b1 ion) and more y-series ions, and their peptide sequence coverage was almost 100%. The long dual-modified peptides produce b1 ion and more y-series ions, and their peptide sequence coverage was nearly above 90%. Therefore, both carbamylation and the dual modification method could be used to identify the N-terminal amino acid, and the dual modification method was also excellent for the de novo sequencing of the tryptic peptides.
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Affiliation(s)
- Cheng Guo
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
| | - Xuefeng Guo
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
| | - Lei Zhao
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
| | - Dandan Chen
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
| | - Jin Wang
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
| | - Jia Sun
- State Forestry Administration Key Open Laboratory, International Centre for Bamboo and Rattan, Beijing, China
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11
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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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12
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Sanders JD, Greer SM, Brodbelt JS. Integrating Carbamylation and Ultraviolet Photodissociation Mass Spectrometry for Middle-Down Proteomics. Anal Chem 2017; 89:11772-11778. [DOI: 10.1021/acs.analchem.7b03396] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James D. Sanders
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Sylvester M. Greer
- 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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13
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McClory PJ, Håkansson K. Corona Discharge Suppression in Negative Ion Mode Nanoelectrospray Ionization via Trifluoroethanol Addition. Anal Chem 2017; 89:10188-10193. [PMID: 28841300 PMCID: PMC5642034 DOI: 10.1021/acs.analchem.7b01225] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Negative ion mode nanoelectrospray ionization (nESI) is often utilized to analyze acidic compounds, from small molecules to proteins, with mass spectrometry (MS). Under high aqueous solvent conditions, corona discharge is commonly observed at emitter tips, resulting in low ion abundances and reduced nESI needle lifetimes. We have successfully reduced corona discharge in negative ion mode by trace addition of trifluoroethanol (TFE) to aqueous samples. The addition of as little as 0.2% TFE increases aqueous spray stability not only in nESI direct infusion, but also in nanoflow liquid chromatography (nLC)/MS experiments. Negative ion mode spray stability with 0.2% TFE is approximately 6× higher than for strictly aqueous samples. Upon addition of 0.2% TFE to the mobile phase of nLC/MS experiments, tryptic peptide identifications increased from 93 to 111 peptides, resulting in an average protein sequence coverage increase of 18%.
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Affiliation(s)
- Phillip J. McClory
- Department of Chemistry, University of Michigan, 930 North University Ave., Ann Arbor, MI 48109-1055
| | - Kristina Håkansson
- Department of Chemistry, University of Michigan, 930 North University Ave., Ann Arbor, MI 48109-1055
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14
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Greer SM, Holden DD, Fellers R, Kelleher NL, Brodbelt JS. Modulation of Protein Fragmentation Through Carbamylation of Primary Amines. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1587-1599. [PMID: 28374316 PMCID: PMC5624212 DOI: 10.1007/s13361-017-1648-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 02/28/2017] [Accepted: 03/02/2017] [Indexed: 05/23/2023]
Abstract
We evaluate the impact of carbamylation of the primary amines of the side-chains of Lys and the N-termini on the fragmentation of intact protein ions and the chromatographic properties of a mixture of E. coli ribosomal proteins. The fragmentation patterns of the six unmodified and carbamylated proteins obtained by higher energy collision dissociation (HCD) and ultraviolet photodissociation (UVPD) were compared. Carbamylation significantly reduced the total number of protons retained by the protein owing to the conversion of basic primary amines to non-basic carbamates. Carbamylation caused a significant negative impact on fragmentation of the protein by HCD (i.e., reduced sequence coverage and fewer diagnostic fragment ions) consistent with the mobile proton model, which correlates peptide fragmentation with charge distribution and the opportunity for charge-directed pathways. In addition, fragmentation was enhanced near the N- and C-termini upon HCD of carbamylated proteins. For LCMS/MS analysis of E. coli ribosomal proteins, the retention times increased by 16 min on average upon carbamylation, an outcome attributed to the increased hydrophobicity of the proteins after carbamylation. As noted for both the six model proteins and the ribosomal proteins, carbamylation had relatively little impact on the distribution or types of fragment ions product by UVPD, supporting the proposition that the mechanism of UVPD for intact proteins does not reflect the mobile proton model. Graphical Abstract ᅟ.
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Affiliation(s)
- Sylvester M Greer
- Department of Chemistry, University of Texas at Austin, Austin, TX, 78712, USA
| | - Dustin D Holden
- Department of Chemistry, University of Texas at Austin, Austin, TX, 78712, USA
| | - Ryan Fellers
- National Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, IL, 60208, USA
| | - Neil L Kelleher
- National Resource for Translational and Developmental Proteomics, Northwestern University, Evanston, IL, 60208, USA
- Departments of Chemistry, Molecular Biosciences, and the Feinberg School of Medicine, Northwestern University, Evanston, IL, 60208, USA
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, TX, 78712, USA.
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15
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Quick MM, Mehaffey MR, Johns RW, Parker WR, Brodbelt JS. SITS Derivatization of Peptides to Enhance 266 nm Ultraviolet Photodissociation (UVPD). JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1462-1472. [PMID: 28315237 DOI: 10.1007/s13361-017-1650-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/01/2017] [Accepted: 03/03/2017] [Indexed: 06/06/2023]
Abstract
N-terminal derivatization of peptides with the chromogenic reagent 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (SITS) is demonstrated to enhance the efficiency of 266 nm ultraviolet photodissociation (UVPD). Attachment of the chromophore results in a mass shift of 454 Da and provides significant gains in the number and abundances of diagnostic fragment ions upon UVPD. Activation of SITS-tagged peptides with 266 nm UVPD leads to many fragment ions akin to the a/b/y ions commonly produced by CID, along with other sequence ions (c, x, and z) typically accessed through higher energy pathways. Extreme bias towards C-terminal fragment ions is observed upon activation of SITS-tagged peptides using multiple 266 nm laser pulses. Due to the high reaction efficiency of the isothiocyanate coupling to the N-terminus of peptides, we demonstrate the ability to adapt this strategy to a high-throughput LC-MS/MS workflow with 266 nm UVPD. Graphical Abstract ᅟ.
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Affiliation(s)
- M Montana Quick
- Department of Chemistry, University of Texas, Austin, TX, 78712, USA
| | - M Rachel Mehaffey
- Department of Chemistry, University of Texas, Austin, TX, 78712, USA
| | - Robert W Johns
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
- McKetta Department of Chemical Engineering, University of Texas, Austin, TX, 78712, USA
| | - W Ryan Parker
- Department of Chemistry, University of Texas, Austin, TX, 78712, USA
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16
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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: 8] [Impact Index Per Article: 1.1] [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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17
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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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18
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Robinson MR, Brodbelt JS. Integrating Weak Anion Exchange and Ultraviolet Photodissociation Mass Spectrometry with Strategic Modulation of Peptide Basicity for the Enrichment of Sulfopeptides. Anal Chem 2016; 88:11037-11045. [PMID: 27768275 DOI: 10.1021/acs.analchem.6b02899] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Tyrosine sulfation is an important post-translational modification but remains difficult to detect in biological samples owing to its low stoichiometric abundance and the lack of effective enrichment methods. In the present study, weak anion exchange (WAX) is evaluated for the enrichment of sulfopeptides that have been modified via carbamylation to convert all primary amines to less basic carbamates. The decrease in basicity enhanced the binding of carbamylated sulfopeptides to WAX resin relative to nonsulfated peptides. Upon elution and electrospray ionization in the negative mode, ultraviolet photodissociation (UVPD) was applied for peptide sequencing. Application of the method to a tryptic digest of bovine coagulation factor V resulted in identification of sulfation on tyrosine 1513.
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Affiliation(s)
- Michelle R Robinson
- Department of Chemistry, The University of Texas , Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, The University of Texas , Austin, Texas 78712, United States
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19
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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: 37] [Impact Index Per Article: 4.6] [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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20
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Parker WR, Holden DD, Cotham VC, Xu H, Brodbelt JS. Cysteine-Selective Peptide Identification: Selenium-Based Chromophore for Selective S-Se Bond Cleavage with 266 nm Ultraviolet Photodissociation. Anal Chem 2016; 88:7222-9. [PMID: 27320857 DOI: 10.1021/acs.analchem.6b01465] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The tremendous number of peptides identified in current bottom-up mass spectrometric workflows, although impressive for high-throughput proteomics, results in little selectivity for more targeted applications. We describe a strategy for cysteine-selective proteomics based on a tagging method that installs a S-Se bond in peptides that is cleavable upon 266 nm ultraviolet photodissociation (UVPD). The alkylating reagent, N-(phenylseleno)phthalimide (NPSP), reacts with free thiols in cysteine residues and attaches a chromogenic benzeneselenol (SePh) group. Upon irradiation of tagged peptides with 266 nm photons, the S-Se bond is selectively cleaved, releasing a benzeneselenol moiety corresponding to a neutral loss of 156 Da per cysteine. Herein we demonstrate a new MS/MS scan mode, UVPDnLossCID, which facilitates selective screening of cysteine-containing peptides. A "prescreening" event occurs by activation of the top N peptide ions by 266 nm UVPD. Peptides exhibiting a neutral loss corresponding to one or more SePh groups are reactivated and sequenced by CID. Because of the low frequency of cysteine in the proteome, unique cysteine-containing peptides may serve as surrogates for entire proteins. UVPDnLossCID does not generate as many peptide spectrum matches (PSMs) as conventional bottom-up methods; however, UVPDnLossCID provides far greater selectivity.
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Affiliation(s)
- W Ryan Parker
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | - Dustin D Holden
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | - Victoria C Cotham
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | - Hua Xu
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, University of Texas , Austin, Texas 78712, United States
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21
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Online coupling of high-resolution chromatography with extreme UV photon activation tandem mass spectrometry: Application to the structural investigation of complex glycans by dissociative photoionization. Anal Chim Acta 2016; 933:1-9. [PMID: 27496992 DOI: 10.1016/j.aca.2016.05.036] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/17/2016] [Accepted: 05/22/2016] [Indexed: 01/09/2023]
Abstract
The activation of ions by extreme-energy photons (XUV) produced by a synchrotron radiation beamline is a powerful method for characterizing complex glycans using tandem mass spectrometry (MS). As previously described, this activation method leads to rich fragmentation spectra with many structurally valuable cross-ring cleavages while maintaining labile modifications on the glycan structures. However, until now, the tandem MS event was too long to be compatible with liquid chromatography elution times. In this work, the duty cycle of the activation and detection of fragments was shortened, and the background signal on the spectra was drastically reduced. Both improvements allowed, for the first time, the successful coupling of a UHPLC system to XUV-activated tandem MS. The approach was used to characterize a complex mixture of oligo-porphyrans, which are a class of highly sulfated oligosaccharides, in a fully automated way. Due to an enhanced dynamic range and an increased sensitivity, some hypothetical structures of low abundance have been unequivocally confirmed in this study and others have been revised. Some previously undescribed species of oligo-porphyrans that exhibit lateral branching have been fully resolved. This work contributes to the scarce knowledge of the structure of porphyrans in red algae and pushes the current capacities of XUV-activation tandem MS by demonstrating the possibility of a direct coupling with UHPLC. This study will considerably broaden the applicability and practicality of this method in many fields of analytical biology.
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22
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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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23
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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: 45] [Impact Index Per Article: 5.0] [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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