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Ghosh D, Rosu F, Gabelica V. Negative Electrospray Supercharging Mechanisms of Nucleic Acid Structures. Anal Chem 2022; 94:15386-15394. [DOI: 10.1021/acs.analchem.2c03187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Debasmita Ghosh
- INSERM, CNRS, Acides Nucléiques: Régulations Naturelle et Artificielle (ARNA, U1212, UMR5320), IECB, Univ. Bordeaux, 33600Pessac, France
| | - Frédéric Rosu
- CNRS, INSERM, Institut Européen de Chimie et Biologie (IECB, UAR3033, US001), Univ. Bordeaux, 33600Pessac, France
| | - Valérie Gabelica
- INSERM, CNRS, Acides Nucléiques: Régulations Naturelle et Artificielle (ARNA, U1212, UMR5320), IECB, Univ. Bordeaux, 33600Pessac, France
- CNRS, INSERM, Institut Européen de Chimie et Biologie (IECB, UAR3033, US001), Univ. Bordeaux, 33600Pessac, France
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2
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de Kleijne VH, Heijboer AC, de Jonge R, Ackermans MT. Supercharging reagents in LC-MS/MS hormone analyses: Enhancing ionization, not limit of quantification. J Chromatogr B Analyt Technol Biomed Life Sci 2022; 1204:123337. [PMID: 35709668 DOI: 10.1016/j.jchromb.2022.123337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 10/18/2022]
Abstract
One of the critical steps during LC-MS/MS hormone analyses that affects the sensitivity of the assay is the ionization process. Enhancing ionization efficiencies by the addition of supercharging reagents might be one way to improve sensitivity and reduce the limit of quantification (LOQ). Therefore, we investigated whether the addition of the supercharging reagents m-nitrobenzyl alcohol (m-NBA), sulfolane, propylene carbonate, and o-nitroanisole (o-NA) increased ionization efficiency and improved assay LOQ of insulin, oxytocin, sex steroids, and corticosteroids in test solutions. Additionally, the influence of the supercharging reagents was tested in serum samples after sample pretreatment to determine whether ionization would be enhanced similarly in routine analyses and, subsequently, lead to improved sensitivity. The screening experiments showed that the impact of the supercharging reagents varied for each hormone; although the addition of m-NBA increased the signal of all hormones, the other reagents only enhanced ionization efficiencies for some hormones. While the addition of 0.05 v/v% m-NBA and 0.05 v/v% o-NA did result in an increase in peak area in both test solutions and serum samples, it did not significantly improve the signal-to-noise ratio, as a simultaneous increase in noise was observed. In conclusion, even though supercharging reagents can enhance ionization efficiencies of hormones significantly, the addition of these reagents does not result in an improved LOQ for hormone measurements with LC-MS/MS.
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Affiliation(s)
- Vera H de Kleijne
- Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Meibergdreef 9, Amsterdam, The Netherlands; Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Boelelaan 1117, Amsterdam, The Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands.
| | - Annemieke C Heijboer
- Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Meibergdreef 9, Amsterdam, The Netherlands; Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Boelelaan 1117, Amsterdam, The Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
| | - Robert de Jonge
- Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Meibergdreef 9, Amsterdam, The Netherlands; Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Boelelaan 1117, Amsterdam, The Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
| | - Mariëtte T Ackermans
- Amsterdam UMC location University of Amsterdam, Department of Clinical Chemistry, Endocrine Laboratory, Meibergdreef 9, Amsterdam, The Netherlands; Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
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3
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Källsten M, Visanu D, Pijnappel M, Lehmann F, Bergquist J, Lind SB, Kovac L. Potential Use of Supercharging Agents for Improved Mass Spectrometric Analysis of Monoclonal Antibodies and Antibody-Drug Conjugates. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1161-1167. [PMID: 35704800 DOI: 10.1021/jasms.2c00008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The addition of supercharging (SC) reagents in electrospray ionization coupled mass spectrometry (ESI-MS) has demonstrated several advantages for protein analysis such as reduced required mass range of the instrument, narrowed charge-state distribution, increased sensitivity, and adduct suppression. The potential use of SC reagents to improve analyses of larger and complex protein molecules such as monoclonal antibodies and antibody-drug conjugates (ADCs) has not been previously reported. In this study, the effect of seven SC reagents (meta-nitrobenzyl alcohol (m-NBA), dimethyl sulfoxide (DMSO), ortho-nitroanisole (o-NA), propane sultone (PS), ethylene carbonate (EC), propylene carbonate (PC), and sulfolane) on ESI-MS acquired spectra of deglycosylated, intact, and reduced trastuzumab and a vcMMAE-trastuzumab ADC was investigated under denaturing conditions. The addition of any of the SC reagents resulted in a higher average charge state observed for all tested reagents for both trastuzumab and the ADC and a narrower charge-state envelope for o-NA and 1% sulfolane for trastuzumab. However, improved peak shapes or increased sensitivity was observed for several reagents, overall increasing the spectra quality. Finally, it was shown that SC reagents can be safely used for ADC analysis without impacting the obtained drug-to-antibody (DAR) values, as all DAR values were within 0.1 from the control sample.
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Affiliation(s)
- Malin Källsten
- Analytical Chemistry, Department of Chemistry-BMC, Uppsala University, S75237 Uppsala, Sweden
- Recipharm OT Chemistry AB, S75450 Uppsala, Sweden
| | - Diana Visanu
- Recipharm OT Chemistry AB, S75450 Uppsala, Sweden
| | | | | | - Jonas Bergquist
- Analytical Chemistry, Department of Chemistry-BMC, Uppsala University, S75237 Uppsala, Sweden
| | - Sara Bergström Lind
- Analytical Chemistry, Department of Chemistry-BMC, Uppsala University, S75237 Uppsala, Sweden
| | - Lucia Kovac
- Recipharm OT Chemistry AB, S75450 Uppsala, Sweden
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4
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Microfluidic ion stripper for removal of trifluoroacetic acid from mobile phases used in HILIC-MS of intact proteins. Anal Bioanal Chem 2021; 413:4379-4386. [PMID: 34050389 PMCID: PMC8245364 DOI: 10.1007/s00216-021-03414-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 05/02/2021] [Accepted: 05/18/2021] [Indexed: 11/01/2022]
Abstract
Trifluoroacetic acid (TFA) is commonly used as mobile phase additive to improve retention and peak shape characteristics in hydrophilic interaction liquid chromatography (HILIC) of intact proteins. However, when using electrospray ionization-mass spectrometry (ESI-MS) detection, TFA may cause ionization suppression and adduct formation, leading to reduced analyte sensitivity. To address this, we describe a membrane-based microfluidic chip with multiple parallel channels for the selective post-column removal of TFA anions from HILIC. An anion-exchange membrane was used to physically separate the column effluent from a stripper flow solution comprising acetonitrile, formic acid, and propionic acid. The exchange of ions allowed the post-column removal of TFA used during HILIC separation of model proteins. The multichannel design of the device allows the use of flow rates of 0.2 mL/min without the need for a flow splitter, using mobile phases containing 0.1% TFA (13 mM). Separation selectivity and efficiency were maintained (with minor band broadening effects) while increasing the signal intensity and peak areas by improving ionization and reducing TFA adduct formation.
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Martin LM, Konermann L. Sulfolane-Induced Supercharging of Electrosprayed Salt Clusters: An Experimental/Computational Perspective. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:486-496. [PMID: 33334096 DOI: 10.1021/jasms.0c00377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
It is well-known that supercharging agents (SCAs) such as sulfolane enhance the electrospray ionization (ESI) charge states of proteins, although the mechanistic origins of this effect remain contentious. Only very few studies have explored SCA effects on analytes other than proteins or peptides. This work examines how sulfolane affects electrosprayed NaI salt clusters. Such alkali metal halide clusters have played a key role for earlier ESI mechanistic studies, making them interesting targets for supercharging investigations. ESI of aqueous NaI solutions predominantly generated singly charged [NanI(n-1)]+ clusters. The addition of sulfolane resulted in abundant doubly charged [NanI(n-2)Sulfolanes]2+ species. These experimental data for the first time demonstrate that electrosprayed salt clusters can undergo supercharging. Molecular dynamics (MD) simulations of aqueous ESI nanodroplets containing Na+/I- with and without sulfolane were conducted to obtain atomistic insights into the supercharging mechanism. The simulations produced [NanIi]z+ and [NanIiSulfolanes]z+ clusters similar to those observed experimentally. The MD trajectories demonstrated that these clusters were released into the gas phase upon droplet evaporation to dryness, in line with the charged residue model. Sulfolane was found to evaporate much more slowly than water. This slow evaporation, in conjunction with the large dipole moment of sulfolane, resulted in electrostatic stabilization of the shrinking ESI droplets and the final clusters. Hence, charge-dipole stabilization causes the sulfolane-containing droplets and clusters to retain more charge, thereby providing the mechanistic foundation of salt cluster supercharging.
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Affiliation(s)
- Leanne M Martin
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Abaye DA, Agbo IA, Nielsen BV. Current perspectives on supercharging reagents in electrospray ionization mass spectrometry. RSC Adv 2021; 11:20355-20369. [PMID: 35479879 PMCID: PMC9033978 DOI: 10.1039/d1ra00745a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Accepted: 06/02/2021] [Indexed: 11/21/2022] Open
Abstract
In electrospray ionization mass spectrometry (ESI-MS), analytes are introduced into the mass spectrometer in typically aqueous-organic solvent mixtures, including pH modifiers. One mechanism for improving the signal intensity and simultaneously increasing the generation of higher charge-state ions is the inclusion of small amounts (approx. <0.5% v/v mobile phase solution) of charge-inducing or supercharging reagents, such as m-nitrobenzyl alcohol, o-nitrobenzyl alcohol, m-nitrobenzonitrile, m-(trifluoromethyl)-benzyl alcohol and sulfolane. We explore the direct and indirect (colligative properties) that have been proposed as responsible for their modes of action during ESI. Of the many theorized mechanisms of ESI, we re-visit the three most popular and highlight how they are impacted by supercharging observations on small ions to large molecules including proteins. We then provide a comprehensive list of 34 supercharging reagents that have been demonstrated in ESI experiments. We include an additional 19 potential candidate isomers as supercharging reagents and comment on their broad physico-chemical properties. It is becoming increasingly obvious that advances in technology and improved ion source design, analyzers e.g. the use of ion mobility, ion trap, circular dichroism (CD) spectroscopy, together with computer modeling are increasing the knowledge base and, together with the untested isomers and yet-to-be unearthed ones, offer opportunities for further research and application in other areas of polymer research. A simple illustration of the positive electrospray ionization (ESI) environment.![]()
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Affiliation(s)
- Daniel A. Abaye
- Department of Basic Sciences
- School of Basic and Biomedical Sciences
- University of Health and Allied Sciences
- Ho
- Ghana
| | - Irene A. Agbo
- Department of Basic Sciences
- School of Basic and Biomedical Sciences
- University of Health and Allied Sciences
- Ho
- Ghana
| | - Birthe V. Nielsen
- School of Science
- Faculty of Engineering and Science
- University of Greenwich
- Kent
- UK
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Bongaerts J, Segers K, Van Oudenhove L, Van Wanseele Y, Van Hulle M, De Bundel D, Mangelings D, Smolders I, Vander Heyden Y, Van Eeckhaut A. A comparative study of UniSpray and electrospray sources for the ionization of neuropeptides in liquid chromatography tandem mass spectrometry. J Chromatogr A 2020; 1628:461462. [PMID: 32822992 DOI: 10.1016/j.chroma.2020.461462] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/17/2020] [Accepted: 08/05/2020] [Indexed: 01/21/2023]
Abstract
Despite the extensive use of electrospray ionization (ESI) for the quantification of neuropeptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS), poor ionization and transmission efficiency are described for this ionization interface. A new atmospheric pressure ionization source, named UniSpray, was recently developed and commercialized. In this study, the LC-MS performance of this new ionization interface is evaluated and compared with ESI for the quantification of seven neuropeptides. Besides comparison of signal intensities and charge state distributions, also signal-to-noise (S/N) ratios and accuracy and precision were assessed. Additionally, matrix effects of human precipitated plasma and rat microdialysate were evaluated as well as the effect of three supercharging agents on the ionization of the seven neuropeptides. UniSpray ionization resulted in signal intensities four to eight times higher at the optimal capillary/impactor voltage for all seven neuropeptides. S/N values at the other hand only increased by not more than a twofold when the UniSpray source was used. Moreover, UniSpray ionization resulted in a shift towards lower charge states for some neuropeptides. Evaluation of the matrix effects by a post-column infusion set-up resulted in different infusion profiles between ESI and UniSpray. The charge state distributions of the neuropeptides obtained with UniSpray are highly comparable with ESI. Finally, the effect of the supercharging agents on the ionization of the neuropeptides tends to be peptide-dependent with both ionization sources.
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Affiliation(s)
- Jana Bongaerts
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium; Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling (FABI), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Karen Segers
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium; Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling (FABI), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | | | - Yannick Van Wanseele
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | | | - Dimitri De Bundel
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Debby Mangelings
- Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling (FABI), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Ilse Smolders
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Yvan Vander Heyden
- Department of Analytical Chemistry, Applied Chemometrics and Molecular Modelling (FABI), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Ann Van Eeckhaut
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information (FASC), Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium.
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8
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Thinius M, Polaczek C, Langner M, Bräkling S, Haack A, Kersten H, Benter T. Charge Retention/Charge Depletion in ESI-MS: Experimental Evidence. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:773-784. [PMID: 32150403 DOI: 10.1021/jasms.9b00044] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The effects of liquid and gas phase additives (chemical modifiers) on the ion signal distribution for Substance P (SP), recorded with a nanoelectrospray setup, are evaluated. Depletion of the higher charge state of Substance P ([SP+3H]3+) is observed with polar protic gas phase modifiers. This is attributed to their ability to form larger hydrogen-bonded clusters, whose proton affinity increases with cluster size. These clusters are able to deprotonate the higher charge state. "Supercharging agents" (SCAs) as well as aprotic polar gas phase modifiers, which promote the retention of the higher charge state of Substance P, do not form such large clusters under the given conditions and are therefore not able to deprotonate Substance P. Both SCAs and aprotic modifiers form clusters with the higher charge state, leading to stabilization of the charge. Whereas supercharging agents have low vapor pressures and are therefore enriched in late-stage electrospray droplets, the gas phase modifiers are volatile organic solvents. Collision induced dissociation experiments revealed that the addition of a modifier significantly delays the droplet evaporation and ion release process. This indicates that the droplet takes up the gas phase modifier to a certain extent (accommodation). Depending on the modifier's properties either charge depletion or retention may eventually be promoted.
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Affiliation(s)
- Marco Thinius
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Christine Polaczek
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Markus Langner
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Steffen Bräkling
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Alexander Haack
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Hendrik Kersten
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
| | - Thorsten Benter
- Department of Physical and Theoretical Chemistry, University of Wuppertal, Gauss Str. 20, 42119 Wuppertal, Germany
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9
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Persaud RR, Dieke NE, Jing X, Lambert S, Parsa N, Hartmann E, Vincent JB, Cassady CJ, Dixon DA. Mechanistic Study of Enhanced Protonation by Chromium(III) in Electrospray Ionization: A Superacid Bound to a Peptide. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:308-318. [PMID: 32031389 DOI: 10.1021/jasms.9b00078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Addition of trivalent chromium, Cr(III), to solutions undergoing electrospray ionization (ESI) enhances protonation and leads to formation of [M + 2H]2+ for peptides that normally produce [M + H]+. This effect is explored using electronic structure calculations at the density functional theory (DFT) level to predict the energetics of various species that are potentially important to the mechanism. Gas- and solution-phase reaction free energies for glycine and its anion reacting with [Cr(III)(H2O)6]3+ and for dehydration of these species have been predicted, where glycine is used as a simple model for a peptide. For comparison, calculations were also performed with Fe(III), Al(III), Sc(III), Y(III), and La(III). Removal of water from these complexes, as would occur during the ESI desolvation process, results in species that are highly acidic. The calculated pKa of Cr(III) with a single solvation shell is -10.8, making [Cr(III)(H2O)6]3+ a superacid that is more acidic than sulfuric acid (pKa = -8.8). Binding to glycine requires removal of two aqua ligands, which gives [Cr(III)(H2O)4]3+ that has an extremely acidic pKa of -28.8. Removal of additional water further enhances acidity, reaching a pKa of -84.7 for [Cr(III)(H2O)]3+. A mechanism for enhanced protonation is proposed that incorporates computational and experiment results, as well as information on the known chemistry of Cr(III), which is substitutionally inert. The initial step involves binding of [Cr(III)(H2O)4]3+ to the deprotonated C-terminus of a peptide. As the drying process during ESI strips water from the complex, the resulting superacid transfers protons to the bound peptide, eventually leading to formation of [M + 2H]2+.
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Affiliation(s)
- Rudradatt R Persaud
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Nnenna E Dieke
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Xinyao Jing
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Skyler Lambert
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Nicholas Parsa
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Elizabeth Hartmann
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - John B Vincent
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - Carolyn J Cassady
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
| | - David A Dixon
- Department of Chemistry & Biochemistry , The University of Alabama , Tuscaloosa , Alabama 35487-0336 , United States
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10
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Feng L, Gong X, Song J, Zhai R, Huang Z, Jiang Y, Fang X, Dai X. Strong Acid Anions Significantly Increasing the Charge State of Proteins during Electrospray Ionization. Anal Chem 2020; 92:1770-1779. [PMID: 31769658 DOI: 10.1021/acs.analchem.9b03416] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulation of protein's charge state in electrospray is of great importance to the analysis of proteins. Different methods have been developed so far to increase the charge state of proteins. In this work, we investigated the influence of different anions on the charge state of proteins. Both strong acid anions and weak acid anions were taken into consideration. The results showed that the presence of 5 mM strong acid anions in acidic solutions could significantly increase the charge state of proteins. In comparison, weak acid anions with the same concentration in solution had little impact on the charge state of proteins. The species of the cations in the samples had very limited influence on the charge state. The presence of a certain amount of acid in sample solution was critical to the effect of strong acid anions. Almost no increase of the charge state was observed when no acid was added to the samples. However, remarkable increase of the charge state of myoglobin (Mb) was observed when 0.001% (v/v) acetic acid (HAc) was added to the sample together with 5 mM sodium chloride (NaCl). A higher concentration of acid in samples would further enhance the effect of strong acid anions on the increase of the charge state. Further investigations into the mechanism revealed that the effect of the strong acid anions on the charge state of proteins was based on the unfolding of the protein molecules during electrospray ionization (ESI). The interactions among H+, anions, and protein molecules were so strong that it caused the unfolding of protein molecules and resulted in the increasing of proteins' charge states. The key factor that made strong acid anions and weak acid anions different in the results was the hydrolysis of the weak acid anions in acidic solutions. The present work furthers our understanding about electrospray, as well as the regulation of protein charge state. The presence of strong acid anions in acidic solutions can significantly influence the charge state of proteins in electrospray. Attention should be paid to this when regulating the charge state of proteins.
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Affiliation(s)
- Lulu Feng
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Xiaoyun Gong
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Jiafeng Song
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Rui Zhai
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Zejian Huang
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - You Jiang
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Xiang Fang
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Xinhua Dai
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
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11
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Martin LM, Konermann L. Enhancing Protein Electrospray Charge States by Multivalent Metal Ions: Mechanistic Insights from MD Simulations and Mass Spectrometry Experiments. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:25-33. [PMID: 32881517 DOI: 10.1021/jasms.9b00027] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The structure and reactivity of electrosprayed protein ions is governed by their net charge. Native proteins in non-denaturing aqueous solutions produce low charge states. More highly charged ions are formed when electrospraying proteins that are unfolded and/or exposed to organic supercharging agents. Numerous studies have explored the electrospray process under these various conditions. One phenomenon that has received surprisingly little attention is the charge enhancement caused by multivalent metal ions such as La3+ when electrospraying proteins out of non-denaturing solutions. Here, we conducted mass spectrometry and ion mobility spectrometry experiments, in combination with molecular dynamics (MD) simulations, to uncover the mechanistic basis of this charge enhancement. MD simulations of aqueous ESI droplets reproduced the experimental observation that La3+ boosts protein charge states relative to monovalent metals (e.g., Na+). The simulations showed that gaseous proteins were released by solvent evaporation to dryness, consistent with the charged residue model. Metal ion ejection kept the shrinking droplets close to the Rayleigh limit until ∼99% of the solvent had left. For droplets charged with Na+, metal adduction during the final stage of solvent evaporation produced low protein charge states. Droplets containing La3+ showed a very different behavior. The trivalent nature of La3+ favored adduction to the protein at a very early stage, when most of the solvent had not evaporated yet. This irreversible binding via multidentate contacts suppressed La3+ ejection from the vanishing droplets, such that the resulting gaseous proteins carried significantly more charge. Our results illustrate that MD simulations are suitable for uncovering intricate aspects of electrospray mechanisms, paving the way toward an atomistic understanding of mass spectrometry based analytical workflows.
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Affiliation(s)
- Leanne M Martin
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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12
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Khanal DD, Baghdady YZ, Figard BJ, Schug KA. Supercharging and multiple reaction monitoring of high-molecular-weight intact proteins using triple quadrupole mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:821-830. [PMID: 30791152 DOI: 10.1002/rcm.8418] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 02/16/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
RATIONALE Different supercharging agents were tested to study their effect on the intensity and charge state distributions of high-molecular-weight intact proteins. The goal of this work was to increase chargeability and ionization efficiency for proteins ranging from 66 to 150 kDa, to enable subsequent optimization of multiple reaction monitoring (MRM) mode transitions with a triple quadrupole mass spectrometer for potential top-down quantitative analysis. METHODS Supercharging agents, such as meta-nitrobenzyl alcohol (m-NBA), dimethylsulfoxide, trifluoroethanol (TFE), and sulfolane were tested in different concentrations in 50/50 acetonitrile/water with 0.5% formic acid to examine the electrospray ionization response for three model proteins: bovine serum albumin (66 kDa), holo-transferrin (78 kDa), and immunoglobulin G (150 kDa). The settings of ionization source temperature and mobile phase flow rate were also examined. MRM transitions were developed for a wide range of precursor ions for each protein, and limits of detection were determined for the proteins in the presence of favorable additive combinations. RESULTS For most of the proteins, m-NBA (1%) and TFE (5%) worked most effectively, both to shift the charge state and increase intensity. This is the first report of the use of TFE as an effective agent for both increasing protein chargeability and ionization response. TFE increased ionization efficiency between 3- and 14-fold for the model proteins studied. Increases in both source temperature and flow rate reduced the magnitude of the average charge state observed. The MRM transitions of six to eight different precursor ions of the proteins were optimized and limits of detection in the nanogram quantity on column were determined. CONCLUSIONS The feasibility for top-down quantitative analysis of high-molecular-weight proteins with a triple quadrupole mass spectrometer was demonstrated. Further, additives such as TFE can be highly beneficial for increased chargeability and response of the proteins.
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Affiliation(s)
- Durga D Khanal
- Department of Chemistry and Biochemistry, The University of Texas Arlington, Arlington, TX, USA
| | - Yehia Z Baghdady
- Department of Chemistry and Biochemistry, The University of Texas Arlington, Arlington, TX, USA
| | - Benjamin J Figard
- Shimadzu Scientific Instruments, Inc., South Central Region (SCN), Houston, TX, USA
| | - Kevin A Schug
- Department of Chemistry and Biochemistry, The University of Texas Arlington, Arlington, TX, USA
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13
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Peters I, Metwally H, Konermann L. Mechanism of Electrospray Supercharging for Unfolded Proteins: Solvent-Mediated Stabilization of Protonated Sites During Chain Ejection. Anal Chem 2019; 91:6943-6952. [DOI: 10.1021/acs.analchem.9b01470] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Insa Peters
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Haidy Metwally
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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14
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Ke M, Zhang H, Ding J, Xiong X, Li F, Chingin K, Kou W, Liu A, Zhu T, Fang X, Chen H. Generating Supercharged Protein Ions for Breath Analysis by Extractive Electrospray Ionization Mass Spectrometry. Anal Chem 2019; 91:3215-3220. [DOI: 10.1021/acs.analchem.8b03114] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mufang Ke
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People’s Republic of China
| | - Hua Zhang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People’s Republic of China
| | - Jianhua Ding
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, People’s Republic of China
| | - Xingchuang Xiong
- National Institute of Metrology, Beijing 100029, People’s Republic of China
| | - Fenglei Li
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, People’s Republic of China
| | - Konstantin Chingin
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, People’s Republic of China
| | - Wei Kou
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People’s Republic of China
| | - Aiying Liu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People’s Republic of China
| | - Tenggao Zhu
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, People’s Republic of China
| | - Xiang Fang
- National Institute of Metrology, Beijing 100029, People’s Republic of China
| | - Huanwen Chen
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, People’s Republic of China
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15
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Gong X, Li C, Zhai R, Xie J, Jiang Y, Fang X. Supercharging of Proteins by Salts during Polarity Reversed Nano-Electrospray Ionization. Anal Chem 2019; 91:1826-1837. [PMID: 30620564 DOI: 10.1021/acs.analchem.8b02759] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Supercharging is beneficial in many ways to the analysis of proteins by mass spectrometry (MS). In this work, a novel supercharging method was developed. It made use of our previously developed ionization technique: namely, polarity reversed nanoelectrospray ionization (PR-nESI) for the ionization of proteins. Supercharging of proteins was achieved by just adding 1-10 mM of a salt to the sample, such as sodium chloride (NaCl). The charge state of proteins obtained by our method was significantly higher than that by nano-ESI with 1% (v/v) acetic acid (HAc). Different kinds of salts were investigated. Salts with strong acid anions were capable of supercharging proteins, including chlorides, bromides, iodides, and nitrates. The signal intensity and signal to noise ratio ( S/ N) of proteins were increased at the same time. Phosphates were also found to have a supercharging effect, due to the fact that phosphoric acid was a medium-strong acid. In comparison, salts with weak acid anions had no supercharging effect, such as carbonates, sulfides, acetates, and formates. The species of the salt anion was critical to the supercharging effect, while the species of the salt cation showed little influence on the supercharging effect. Investigations were made into the mechanism of our method. The supercharging effect was caused by interactions between protein molecules and salt anions, as well as the influence of protons. The present work offered us an alternative way for the supercharging of proteins. The use of common salts for supercharging made the procedure more convenient. The concentration of salts needed for supercharging was much lower than those conventionally used for supercharging reagents. Taking into consideration the fact that many biological samples are buffered with phosphates and chlorides, these samples could be directly supercharged by our method without any additional additives. Furthermore, as many salts are nontoxic and can easily be found in a chemical laboratory, the use of salts for supercharging would be a much more practical and economical choice. In addition, the present work also furthered our understandings about the mechanism of supercharging, as well as electrospray.
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Affiliation(s)
- Xiaoyun Gong
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Chang Li
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Rui Zhai
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Jie Xie
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - You Jiang
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
| | - Xiang Fang
- Mass Spectrometry Engineering Technology Research Center, Center for Advanced Measurement Science , National Institute of Metrology , Beijing 100029 , People's Republic of China
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16
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Konermann L, Metwally H, Duez Q, Peters I. Charging and supercharging of proteins for mass spectrometry: recent insights into the mechanisms of electrospray ionization. Analyst 2019; 144:6157-6171. [DOI: 10.1039/c9an01201j] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Molecular dynamics simulations have uncovered mechanistic details of the protein ESI process under various experimental conditions.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry
- The University of Western Ontario
- London
- Canada
| | - Haidy Metwally
- Department of Chemistry
- The University of Western Ontario
- London
- Canada
| | - Quentin Duez
- Department of Chemistry
- The University of Western Ontario
- London
- Canada
| | - Insa Peters
- Department of Chemistry
- The University of Western Ontario
- London
- Canada
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17
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Foley EDB, Zenaidee MA, Tabor RF, Ho J, Beves JE, Donald WA. On the mechanism of protein supercharging in electrospray ionisation mass spectrometry: Effects on charging of additives with short- and long-chain alkyl constituents with carbonate and sulphite terminal groups. Anal Chim Acta X 2018; 1:100004. [PMID: 33186415 PMCID: PMC7587038 DOI: 10.1016/j.acax.2018.100004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 11/16/2018] [Accepted: 12/21/2018] [Indexed: 01/26/2023] Open
Abstract
Small organic molecules are used as solution additives in electrospray ionisation mass spectrometry (ESI-MS) to increase the charge states of protein ions and improve the performance of intact protein analysis by tandem mass spectrometry. The properties of the additives that are responsible for their charge-enhancing effects (e.g. dipole moment, gas-phase basicity, Brønsted basicity, and surface tension) have been debated in the literature. We report a series of solution additives for ESI-MS based on cyclic alkyl carbonates and sulphites that have alkyl chains that are from two to ten methylene units long. The extent of charging of [Val [5]]-angiotensin II, cytochrome c, carbonic anhydrase II, and bovine serum albumin in ESI-MS using the additives was measured. For both the alkyl carbonate and sulphite additives with up to four methylene units, ion charging increased as the side chain lengths of the additives increased. At a critical alkyl chain length of four methylene units, protein ion charge states decreased as the chain length increased. The dipole moments, gas-phase basicity values, and Brønsted basicities (i.e. the pK a of the conjugate acids) of the additives were obtained using electronic structure calculations, and the surface tensions were measured by pendant drop tensiometry. Because the dipole moments, gas-phase basicities, and pK a values of the additives did not depend significantly on the alkyl chain lengths of the additives and the extent of charging depended strongly on the chain lengths, these data indicate that these three additive properties do not correlate with protein charging under these conditions. For the additives with alkyl chains at or above the critical length, the surface tension of the additives decreased as the length of the side chain decreased, which correlated well with the decrease in protein charging. These data are consistent with protein charging being limited by droplet surface tension below a threshold surface tension for these additives. For additives with relatively high surface tensions, protein ion charging increased as the amphiphilicity of the additives increased (and surface tension decreased) which is consistent with protein charging being limited by the emission of charge carriers from highly charged ESI generated droplets.
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Affiliation(s)
- Eric D B Foley
- School of Chemistry, University of New South Wales, Sydney, NSW, Australia, 2052
| | - Muhammad A Zenaidee
- School of Chemistry, University of New South Wales, Sydney, NSW, Australia, 2052
| | - Rico F Tabor
- School of Chemistry, Monash University, Melbourne, VIC, Australia, 3800
| | - Junming Ho
- School of Chemistry, University of New South Wales, Sydney, NSW, Australia, 2052
| | - Jonathon E Beves
- School of Chemistry, University of New South Wales, Sydney, NSW, Australia, 2052
| | - William A Donald
- School of Chemistry, University of New South Wales, Sydney, NSW, Australia, 2052
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18
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Jing X, Edwards KC, Vincent JB, Cassady CJ. The use of chromium(III) complexes to enhance peptide protonation by electrospray ionization mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:1198-1206. [PMID: 30281192 DOI: 10.1002/jms.4297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/27/2018] [Accepted: 09/26/2018] [Indexed: 06/08/2023]
Abstract
The addition of trivalent chromium, Cr(III), reagents to peptide solutions can increase the intensity of doubly protonated peptides, [M + 2H]2+ , through electrospray ionization (ESI). Three model heptapeptides were studied: neutral (AAAAAAA), acidic (AAEEEAA), and basic (AAAKAAA). The neutral and acidic peptides form almost no 2+ ions in the absence of Cr(III). Twenty Cr(III) complexes were used as potential enhanced protonation reagents, including 11 complexes with nonlabile ligands and nine with labile ligands. The complexes that provide the most abundant [M + 2H]2+ , the greatest [M + 2H]2+ to [M + H]+ ratio, and the cleanest mass spectra are [Cr(H2 O)6 ](NO3 )3 ·3H2 O and [Cr(THF)3 ]Cl3 . Anions in Cr(III) reagents can also affect the intensity of [M + 2H]2+ and the [M + 2H]2+ to [M + H]+ ratio through cation-anion interactions. The influence of anions on the extent of peptide protonation follows the trend ClO4 - ˃ SO4 2- ˃ Br- ˃ Cl- ˃ F- ≈ NO3 - . Solvent effects and complexes with varying number of water ligands were investigated to study the importance of water in enhanced protonation. Aqueous solvent systems and Cr(III) complexes that have at least one bound water ligand in solution must be used for successful increase in the intensity of [M + 2H]2+ , which indicates that water is involved in the mechanism of Cr(III)-induced enhanced protonation. The ESI source design is also important because no enhanced protonation was observed using a Z-spray source. The current results suggest that this Cr(III)-induced effect occurs during the ESI desolvation process.
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Affiliation(s)
- Xinyao Jing
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama
| | - Kyle C Edwards
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama
| | - John B Vincent
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama
| | - Carolyn J Cassady
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, Alabama
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19
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Nshanian M, Lakshmanan R, Chen H, Ogorzalek Loo RR, Loo JA. Enhancing Sensitivity of Liquid Chromatography-Mass Spectrometry of Peptides and Proteins Using Supercharging Agents. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2018; 427:157-164. [PMID: 29750076 PMCID: PMC5937529 DOI: 10.1016/j.ijms.2017.12.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Trifluoroacetic acid (TFA) is often used as a mobile phase modifier to enhance reversed phase chromatographic performance. TFA adjusts solution pH and is an ion-pairing agent, but it is not typically suitable for electrospray ionization-mass spectrometry (ESI-MS) and liquid chromatography/MS (LC/MS) because of its significant signal suppression. Supercharging agents elevate peptide and protein charge states in ESI, increasing tandem MS (MS/MS) efficiency. Here, LC/MS protein supercharging was effected by adding agents to LC mobile phase solvents. Significantly, the ionization suppression generally observed with TFA was, for the most part, rescued by supercharging agents, with improved separation efficiency (higher number of theoretical plates) and lowered detection limits.
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Affiliation(s)
- Michael Nshanian
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095
| | - Rajeswari Lakshmanan
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095
| | - Hao Chen
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Edison Biotechnology Institute, Ohio University, Athens, OH 45701
| | - Rachel R. Ogorzalek Loo
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Molecular Biology Institute, and UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, CA 90095
| | - Joseph A. Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Molecular Biology Institute, and UCLA/DOE Institute for Genomics and Proteomics, University of California-Los Angeles, Los Angeles, CA 90095
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20
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Wang H, Yong G, Brown SL, Lee HE, Zenaidee MA, Supuran CT, Donald WA. Supercharging protein ions in native mass spectrometry using theta capillary nanoelectrospray ionization mass spectrometry and cyclic alkylcarbonates. Anal Chim Acta 2018; 1003:1-9. [DOI: 10.1016/j.aca.2017.11.075] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/22/2017] [Accepted: 11/25/2017] [Indexed: 12/27/2022]
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21
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Metwally H, Konermann L. Crown Ether Effects on the Location of Charge Carriers in Electrospray Droplets: Implications for the Mechanism of Protein Charging and Supercharging. Anal Chem 2018; 90:4126-4134. [DOI: 10.1021/acs.analchem.8b00099] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Haidy Metwally
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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22
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Steinkoenig J, Cecchini MM, Reale S, Goldmann AS, Barner-Kowollik C. Supercharging Synthetic Polymers: Mass Spectrometric Access to Nonpolar Synthetic Polymers. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b02018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Jan Steinkoenig
- School
of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George St., QLD
4000, Brisbane, Australia
- Macromolecular
Architectures, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128 Eggenstein-Leopoldshafen, Germany
- Institut für Biologische
Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Martina M. Cecchini
- Dipartimento
di Scienze Fisiche e Chimiche, Università degli Studi dell’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
| | - Samantha Reale
- Dipartimento
di Scienze Fisiche e Chimiche, Università degli Studi dell’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, Italy
| | - Anja S. Goldmann
- School
of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George St., QLD
4000, Brisbane, Australia
- Macromolecular
Architectures, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128 Eggenstein-Leopoldshafen, Germany
- Institut für Biologische
Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Christopher Barner-Kowollik
- School
of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology (QUT), 2 George St., QLD
4000, Brisbane, Australia
- Macromolecular
Architectures, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76128 Eggenstein-Leopoldshafen, Germany
- Institut für Biologische
Grenzflächen, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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23
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Honarvar E, Venter AR. Ammonium Bicarbonate Addition Improves the Detection of Proteins by Desorption Electrospray Ionization Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:1109-1117. [PMID: 28315234 DOI: 10.1007/s13361-017-1628-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Revised: 01/26/2017] [Accepted: 02/09/2017] [Indexed: 05/11/2023]
Abstract
The analysis of protein by desorption electrospray ionization mass spectrometry (DESI-MS) is considered impractical due to a mass-dependent loss in sensitivity with increase in protein molecular weights. With the addition of ammonium bicarbonate to the DESI-MS analysis the sensitivity towards proteins by DESI was improved. The signal to noise ratio (S/N) improvement for a variety of proteins increased between 2- to 3-fold relative to solvent systems containing formic acid and more than seven times relative to aqueous methanol spray solvents. Three methods for ammonium bicarbonate addition during DESI-MS were investigated. The additive delivered improvements in S/N whether it was mixed with the analyte prior to sample deposition, applied over pre-prepared samples, or simply added to the desorption spray solvent. The improvement correlated well with protein pI but not with protein size. Other ammonium or bicarbonate salts did not produce similar improvements in S/N, nor was this improvement in S/N observed for ESI of the same samples. As was previously described for ESI, DESI also caused extensive protein unfolding upon the addition of ammonium bicarbonate. Graphical Abstract ᅟ.
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Affiliation(s)
- Elahe Honarvar
- Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA
| | - Andre R Venter
- Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA.
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24
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Roman GT, Murphy JP. Improving sensitivity and linear dynamic range of intact protein analysis using a robust and easy to use microfluidic device. Analyst 2017; 142:1073-1083. [DOI: 10.1039/c6an02518h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate an integrated microfluidic LC device coupled to a QTOF capable of improving sensitivity and linearity for intact protein analysis while also tuning the charge state distributions (CSD) of whole antibodies.
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25
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Cecchini MM, Steinkoenig J, Reale S, Barner L, Yuan J, Goldmann AS, De Angelis F, Barner-Kowollik C. Universal mass spectrometric analysis of poly(ionic liquid)s. Chem Sci 2016; 7:4912-4921. [PMID: 30155139 PMCID: PMC6018439 DOI: 10.1039/c6sc01347c] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 04/19/2016] [Indexed: 01/15/2023] Open
Abstract
We introduce a universal high resolution mass spectrometric method for the analysis of poly(ionic liquid)s (PILs), which belong to the most challenging polyelectrolytes from an analytical perspective, by fusing high resolution collision-induced dissociation (CID)-Orbitrap mass spectrometry (MS) with supercharging agents as well as quadrupole time-of-flight (QToF) MS. The study includes a wide array of hydrophilic halide-containing PILs, which were analyzed in negative mode. The influence of the core structures (based on imidazolium, triazolium, ammonium, phosphonium and pyridinium moieties), and variable styrene-, acrylate- and vinyl-type IL polymers on the ionization behavior is mapped in detail. Variable end group functionalities were introduced via functional chain transfer agents (CTA) in reversible addition-fragmentation chain transfer (RAFT) polymerization to study their behavior during the MS analysis. Furthermore, the demanding class of vinylimidazolium halide IL polymers was investigated. The current contribution thus introduces a new analytical technology platform for an entire polymer class.
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Affiliation(s)
- Martina M Cecchini
- Dipartimento di Scienze Fisiche e Chimiche , Università degli Studi dell'Aquila , Via Vetoio , Coppito , 67100 , L'Aquila , Italy .
| | - Jan Steinkoenig
- Preparative Macromolecular Chemistry , Institut für Technische Chemie und Polymerchemie , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18 , 76128 Karlsruhe , Germany .
- Institut für Biologische Grenzflächen , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
| | - Samantha Reale
- Dipartimento di Scienze Fisiche e Chimiche , Università degli Studi dell'Aquila , Via Vetoio , Coppito , 67100 , L'Aquila , Italy .
| | - Leonie Barner
- Soft Matter Synthesis Laboratory , Institut für Biologische Grenzflächen , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
| | - Jiayin Yuan
- Max-Planck-Institute of Colloids and Interfaces , Research Campus Golm , 14424 Potsdam , Germany
| | - Anja S Goldmann
- Preparative Macromolecular Chemistry , Institut für Technische Chemie und Polymerchemie , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18 , 76128 Karlsruhe , Germany .
- Institut für Biologische Grenzflächen , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
| | - Francesco De Angelis
- Dipartimento di Scienze Fisiche e Chimiche , Università degli Studi dell'Aquila , Via Vetoio , Coppito , 67100 , L'Aquila , Italy .
| | - Christopher Barner-Kowollik
- Preparative Macromolecular Chemistry , Institut für Technische Chemie und Polymerchemie , Karlsruhe Institute of Technology (KIT) , Engesserstr. 18 , 76128 Karlsruhe , Germany .
- Institut für Biologische Grenzflächen , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
- Soft Matter Synthesis Laboratory , Institut für Biologische Grenzflächen , Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1 , 76344 Eggenstein-Leopoldshafen , Germany
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26
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Liigand P, Kaupmees K, Kruve A. Ionization Efficiency of Doubly Charged Ions Formed from Polyprotic Acids in Electrospray Negative Mode. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1211-8. [PMID: 27044024 DOI: 10.1007/s13361-016-1384-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 03/03/2016] [Accepted: 03/14/2016] [Indexed: 05/25/2023]
Abstract
The ability of polyprotic acids to give doubly charged ions in negative mode electrospray was studied and related to physicochemical properties of the acids via linear discriminant analysis (LDA). It was discovered that the compound has to be strongly acidic (low pK a1 and pK a2) and to have high hydrophobicity (logP ow) to become multiply charged. Ability to give multiply charged ions in ESI/MS cannot be directly predicted from the solution phase acidities. Therefore, for the first time, a quantitative model to predict the charge state of the analyte in ESI/MS is proposed and validated for small anions. Also, a model to predict ionization efficiencies of these analytes was developed. Results indicate that acidity of the analyte, its octanol-water partition coefficient, and charge delocalization are important factors that influence ionization efficiencies as well as charge states of the analytes. The pH of the solvent was also found to be an important factor influencing the ionization efficiency of doubly charged ions. Graphical Abstract ᅟ.
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Affiliation(s)
- Piia Liigand
- Institute of Chemistry, Faculty of Science and Technology, University of Tartu, Ravila 14A, 50411, Tartu, Estonia.
| | - Karl Kaupmees
- Institute of Chemistry, Faculty of Science and Technology, University of Tartu, Ravila 14A, 50411, Tartu, Estonia
| | - Anneli Kruve
- Institute of Chemistry, Faculty of Science and Technology, University of Tartu, Ravila 14A, 50411, Tartu, Estonia
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27
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Going CC, Xia Z, Williams ER. Real-time HD Exchange Kinetics of Proteins from Buffered Aqueous Solution with Electrothermal Supercharging and Top-Down Tandem Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:1019-1027. [PMID: 26919868 PMCID: PMC4865425 DOI: 10.1007/s13361-016-1350-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/21/2016] [Accepted: 01/22/2016] [Indexed: 06/05/2023]
Abstract
Electrothermal supercharging (ETS) with electrospray ionization produces highly charged protein ions from buffered aqueous solutions in which proteins have native folded structures. ETS increases the charge of ribonuclease A by 34%, whereas only a 6% increase in charge occurs for a reduced-alkylated form of this protein, which is unfolded and its structure is ~66% random coil in this solution. These results indicate that protein denaturation that occurs in the ESI droplets is the primary mechanism for ETS. ETS does not affect the extent of solution-phase hydrogen-deuterium exchange (HDX) that occurs for four proteins that have significantly different structures in solution, consistent with a droplet lifetime that is considerably shorter than observable rates of HDX. Rate constants for HDX of ubiquitin are obtained with a spatial resolution of ~1.3 residues with ETS and electron transfer dissociation of the 10+ charge-state using a single capillary containing a few μL of protein solution in which HDX continuously occurs. HDX protection at individual residues with ETS HDX is similar to that with reagent supercharging HDX and with solution-phase NMR, indicating that the high spray potentials required to induce ETS do not lead to HD scrambling. Graphical Abstract ᅟ.
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Affiliation(s)
- Catherine C Going
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Zijie Xia
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
| | - Evan R Williams
- Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA.
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28
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Metwally H, McAllister RG, Popa V, Konermann L. Mechanism of Protein Supercharging by Sulfolane and m-Nitrobenzyl Alcohol: Molecular Dynamics Simulations of the Electrospray Process. Anal Chem 2016; 88:5345-54. [DOI: 10.1021/acs.analchem.6b00650] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Haidy Metwally
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Robert G. McAllister
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Vlad Popa
- Department
of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Lars Konermann
- Department
of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
- Department
of Biochemistry, The University of Western Ontario, London, Ontario N6A 5C1, Canada
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29
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Yao Y, Richards MR, Kitova EN, Klassen JS. Influence of Sulfolane on ESI-MS Measurements of Protein-Ligand Affinities. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:498-506. [PMID: 26667179 DOI: 10.1007/s13361-015-1312-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Revised: 11/22/2015] [Accepted: 11/24/2015] [Indexed: 06/05/2023]
Abstract
The results of an investigation into the influence of sulfolane, a commonly used supercharging agent, on electrospray ionization mass spectrometry (ESI-MS) measurements of protein-ligand affinities are described. Binding measurements carried out on four protein-carbohydrate complexes, lysozyme with β-D-GlcNAc-(1→4)-β-D-GlcNAc-(1→4)-β-D-GlcNAc-(1→4)-D-GlcNAc, a single chain variable fragment and α-D-Gal-(1→2)-[α-D-Abe-(1→3)]-α-D-Man-OCH3, cholera toxin B subunit homopentamer with β-D-Gal-(1→3)-β-D-GalNAc-(1→4)[α-D-Neu5Ac-(2→3)]-β-D-Gal-(1→4)-β-D-Glc, and a fragment of galectin 3 and α-L-Fuc-(1→2)-β-D-Gal-(1→3)-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-β-D-Glc, revealed that sulfolane generally reduces the apparent (as measured by ESI-MS) protein-ligand affinities. To establish the origin of this effect, a detailed study was undertaken using the lysozyme-tetrasaccharide interaction as a model system. Measurements carried out using isothermal titration calorimetry (ITC), circular dichroism, and nuclear magnetic resonance spectroscopies reveal that sulfolane reduces the binding affinity in solution but does not cause any significant change in the higher order structure of lysozyme or to the intermolecular interactions. These observations confirm that changes to the structure of lysozyme in bulk solution are not responsible for the supercharging effect induced by sulfolane. Moreover, the agreement between the ESI-MS and ITC-derived affinities indicates that there is no dissociation of the complex during ESI or in the gas phase (i.e., in-source dissociation). This finding suggests that supercharging of lysozyme by sulfolane is not related to protein unfolding during the ESI process. Binding measurements performed using liquid sample desorption ESI-MS revealed that protein supercharging with sulfolane can be achieved without a reduction in affinity.
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Affiliation(s)
- Yuyu Yao
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - Michele R Richards
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - Elena N Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - John S Klassen
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
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30
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Li J, Santambrogio C, Brocca S, Rossetti G, Carloni P, Grandori R. Conformational effects in protein electrospray-ionization mass spectrometry. MASS SPECTROMETRY REVIEWS 2016; 35:111-22. [PMID: 25952139 DOI: 10.1002/mas.21465] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 01/14/2015] [Indexed: 05/11/2023]
Abstract
Electrospray-ionization mass spectrometry (ESI-MS) is a key tool of structural biology, complementing the information delivered by conventional biochemical and biophysical methods. Yet, the mechanism behind the conformational effects in protein ESI-MS is an object of debate. Two parameters-solvent-accessible surface area (As) and apparent gas-phase basicity (GBapp)-are thought to play a role in controlling the extent of protein ionization during ESI-MS experiments. This review focuses on recent experimental and theoretical investigations concerning the influence of these parameters on ESI-MS results and the structural information that can be derived. The available evidence supports a unified model for the ionization mechanism of folded and unfolded proteins. These data indicate that charge-state distribution (CSD) analysis can provide valuable structural information on normally folded, as well as disordered structures.
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Affiliation(s)
- Jinyu Li
- Computational Biophysics, German Research School for Simulation Sciences, and Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany
- Institute of Biochemistry and Molecular Biology, RWTH Aachen University, 52057 Aachen, Germany
| | - Carlo Santambrogio
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy
| | - Stefania Brocca
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy
| | - Giulia Rossetti
- Computational Biophysics, German Research School for Simulation Sciences, and Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany
- Jülich Supercomputing Centre, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Paolo Carloni
- Computational Biophysics, German Research School for Simulation Sciences, and Computational Biomedicine, Institute for Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Rita Grandori
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy
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31
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Going CC, Xia Z, Williams ER. New supercharging reagents produce highly charged protein ions in native mass spectrometry. Analyst 2015; 140:7184-94. [PMID: 26421324 PMCID: PMC4617834 DOI: 10.1039/c5an01710f] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effectiveness of two new supercharging reagents for producing highly charged ions by electrospray ionization (ESI) from aqueous solutions in which proteins have native structures and reactivities were investigated. In aqueous solution, 2-thiophenone and 4-hydroxymethyl-1,3-dioxolan-2-one (HD) at a concentration of 2% by volume can increase the average charge of cytochrome c and myoglobin by up to 163%, resulting in even higher charge states than those that are produced from water/methanol/acid solutions in which these proteins are denatured. The greatest extent of supercharging occurs in pure water, but these supercharging reagents are also highly effective in aqueous solutions containing 200 mM ammonium acetate buffer commonly used in native mass spectrometry (MS). These reagents are less effective supercharging reagents than m-nitrobenzyl alcohol (m-NBA) and propylene carbonate (PC) when ions are formed from water/methanol/acid. The extent to which loss of the heme group from myoglobin occurs is related to the extent of supercharging. Results from guanidine melts of cytochrome c monitored with tryptophan fluorescence show that the supercharging reagents PC, sulfolane and HD are effective chemical denaturants in solution. These results provide additional evidence for the role of protein structural changes in the electrospray droplet as the primary mechanism for supercharging with these reagents in native MS. These results also demonstrate that for at least some proteins, the formation of highly charged ions from native MS is no longer a significant barrier for obtaining structural information using conventional tandem MS methods.
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Affiliation(s)
- Catherine C Going
- Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
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32
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Cassou CA, Williams ER. Desalting protein ions in native mass spectrometry using supercharging reagents. Analyst 2015; 139:4810-9. [PMID: 25133273 DOI: 10.1039/c4an01085j] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Effects of the supercharging reagents m-NBA and sulfolane on sodium ion adduction to protein ions formed using native mass spectrometry were investigated. There is extensive sodium adduction on protein ions formed by electrospray ionization from aqueous solutions containing millimolar concentrations of NaCl, which can lower sensitivity by distributing the signal of a given charge state over multiple adducted ions and can reduce mass measuring accuracy for large proteins and non-covalent complexes for which individual adducts cannot be resolved. The average number of sodium ions adducted to the most abundant ion formed from ten small (8.6-29 kDa) proteins for which adducts can be resolved is reduced by 58% or 80% on average, respectively, when 1.5% m-NBA or 2.5% sulfolane are added to aqueous solutions containing sodium compared to without the supercharging reagent. Sulfolane is more effective than m-NBA at reducing sodium ion adduction and at preserving non-covalent protein-ligand and protein-protein interactions. Desalting with 2.5% sulfolane enables detection of several glycosylated forms of 79.7 kDa holo-transferrin and NADH bound to the 146 kDa homotetramer LDH, which are otherwise unresolved due to peak broadening from extensive sodium adduction. Although sulfolane is more effective than m-NBA at protein ion desalting, m-NBA reduces salt clusters at high m/z and can increase the signal-to-noise ratios of protein ions by reducing chemical noise. Desalting is likely a result of these supercharging reagents binding sodium ions in solution, thereby reducing the sodium available to adduct to protein ions.
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Affiliation(s)
- Catherine A Cassou
- Department of Chemistry, University of California, B42 Hildebrand Hall, Berkeley, California 94720-1460, USA.
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33
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Going CC, Williams ER. Supercharging with m-Nitrobenzyl Alcohol and Propylene Carbonate: Forming Highly Charged Ions with Extended, Near-Linear Conformations. Anal Chem 2015; 87:3973-80. [DOI: 10.1021/acs.analchem.5b00071] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Catherine C. Going
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460, United States
| | - Evan R. Williams
- Department
of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460, United States
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34
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Feng C, Commodore JJ, Cassady CJ. The use of chromium(III) to supercharge peptides by protonation at low basicity sites. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:347-58. [PMID: 25395012 PMCID: PMC4323856 DOI: 10.1007/s13361-014-1020-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 10/09/2014] [Accepted: 10/13/2014] [Indexed: 05/16/2023]
Abstract
The addition of chromium(III) nitrate to solutions of peptides with seven or more residues greatly increases the formation of doubly protonated peptides, [M + 2H](2+), by electrospray ionization. The test compound heptaalanine has only one highly basic site (the N-terminal amino group) and undergoes almost exclusive single protonation using standard solvents. When Cr(III) is added to the solution, abundant [M + 2H](2+) forms, which involves protonation of the peptide backbone or the C-terminus. Salts of Al(III), Mn(II), Fe(III), Fe(II), Cu(II), Zn (II), Rh(III), La(III), Ce(IV), and Eu(III) were also studied. Although several metal ions slightly enhance protonation, Cr(III) has by far the greatest ability to generate [M + 2H](2+). Cr(III) does not supercharge peptide methyl esters, which suggests that the mechanism involves interaction of Cr(III) with a carboxylic acid group. Other factors may include the high acidity of hexa-aquochromium(III) and the resistance of Cr(III) to reduction. Nitrate salts enhance protonation more than chloride salts and a molar ratio of 10:1 Cr(III):peptide produces the most intense [M + 2H](2+). Cr(III) also supercharges numerous other small peptides, including highly acidic species. For basic peptides, Cr(III) increases the charge state (2+ versus 1+) and causes the number of peptide molecules being protonated to double or triple. Chromium(III) does not supercharge the proteins cytochrome c and myoglobin. The ability of Cr(III) to enhance [M + 2H](2+) intensity may prove useful in tandem mass spectrometry because of the resulting overall increase in signal-to-noise ratio, the fact that [M + 2H](2+) generally dissociate more readily than [M + H](+), and the ability to produce [M + 2H](2+) precursors for electron-based dissociation techniques.
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Affiliation(s)
- Changgeng Feng
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL, 35487, USA
| | | | - Carolyn J. Cassady
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL, 35487, USA
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35
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Clarke DJ, Campopiano DJ. Desalting large protein complexes during native electrospray mass spectrometry by addition of amino acids to the working solution. Analyst 2015; 140:2679-86. [DOI: 10.1039/c4an02334j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A simple method for mitigating the adverse effects of salt adduction during native protein mass spectrometry by addition of amino-acids.
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Affiliation(s)
- David J. Clarke
- School of Chemistry
- University of Edinburgh
- Joseph Black Building
- Edinburgh
- UK
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36
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Li L, Yang SH, Vidova V, Rice EM, Wijeratne AB, Havlíček V, Schug KA. Reversed phase liquid chromatography hyphenated to continuous flow-extractive desorption electrospray ionization-mass spectrometry for analysis and charge state manipulation of undigested proteins. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2015; 21:361-368. [PMID: 26307717 DOI: 10.1255/ejms.1364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The application of continuous flow-extractive desorption electrospray ionization (CF-EDESI), an ambient ionization source demonstrated previously for use with intact protein analysis, is expanded here for the coupling of reversed phase protein separations to mass spectrometry. This configuration allows the introduction of charging additives to enhance detection without affecting the chromatographic separation mechanism. Two demonstrations of the advantages of CF-EDESI are presented in this work. First, a proof-of- principle is presented to demonstrate the applicability of hyphenation of liquid chromatography (LC) to CF- EDESI. LC-CF-EDESI-MS has good sensitivity compared to LC-electrospray ionization (ESI)-mass spectrometry. Second, the supercharging mechanism investigated in CF-EDESI provides an insight into a highly debated supercharging process in ESI. The results indicate that the mechanism of protein charging seen in HPLC-CF-EDESI is different from supercharging phenomena in conventional ESI. The surface tension mechanism and binding mechanism may both contribute to protein supercharging in ESI.
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Affiliation(s)
- Li Li
- Department of Chemistry & Biochemistry, the University of Texas at Arlington, Arlington, Texas, USA.
| | - Samuel H Yang
- Department of Chemistry & Biochemistry, the University of Texas at Arlington, Arlington, Texas, USA..
| | - Veronika Vidova
- Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Vídeňská 1083, 14220, Prague, Czech Republic..
| | - Elisa M Rice
- Department of Chemistry & Biochemistry, the University of Texas at Arlington, Arlington, Texas, USA..
| | - Aruna B Wijeratne
- Department of Chemistry & Biochemistry, the University of Texas at Arlington, Arlington, Texas, USA..
| | - Vladimír Havlíček
- Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Vídeňská 1083, 14220, Prague, Czech Republic. Regional Centre of Advanced Technologies and Materials, Department of Analytical Chemistry, Faculty of Science, Palacky University, 17.listopadu 12, 771 46 Olomouc, Czech Republic..
| | - Kevin A Schug
- Department of Chemistry & Biochemistry, the University of Texas at Arlington, Arlington, Texas, USA..
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37
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Zenaidee MA, Donald WA. Extremely supercharged proteins in mass spectrometry: profiling the pH of electrospray generated droplets, narrowing charge state distributions, and increasing ion fragmentation. Analyst 2015; 140:1894-905. [DOI: 10.1039/c4an02338b] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-performance solutions for supercharging proteins in electrospray ionization were optimized and the origin of the strong dependence of supercharging on acid strength was investigated.
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38
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Douglass KA, Venter AR. On the role of a direct interaction between protein ions and solvent additives during protein supercharging by electrospray ionization mass spectrometry. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2015; 21:641-647. [PMID: 26307743 DOI: 10.1255/ejms.1360] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The addition of certain reagents during the electrospray ionization mass spectrometry of proteins can shift the protein ion signal charge-state distributions (CSDs) to higher average charge states, a phenomenon known as 'supercharging'. The role of reagent gas-phase basicity (GB) during this process was investigated in both the negative and positive ion modes. Reagents with known or calculated GBs were added individually in equimolar amounts to protein solutions which were subsequently electrosprayed for mass spectrometry analysis. Shifts in the CSDs of the protein ion signals were monitored and related to the reagents' GBs. Trends for this data were evaluated for possible insights into a supercharging mechanism involving the direct interaction between supercharging reagent and protein ion. Reagent GB was confirmed to be directly related to the amount of supercharging observed in the negative ion mode. Supercharging in the positive ion mode, on the other hand, showed a maximal trend. Interestingly, a loss of signal and supercharging efficacy was observed for reagents with GBs intermediate within the investigated range, between ~800 and ~840 kJ mol(-1), at the 100 mM concentration used in the present study. The possibility of a direct interaction model for supercharging in the negative and positive ion modes dependent on the GBs of the protein ions and reagents is discussed. In the positive ion mode, supercharging appears to depend on the stability of a proton bridge formed between the reagent and a highly charged protein ion.
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Affiliation(s)
- Kevin A Douglass
- Department of Chemistry, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5413, United States.
| | - Andre R Venter
- D epartment of Chemistry, Western Michigan University, 1903 W Michigan Ave, Kalamazoo, MI 49008-5413, United States.
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39
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Ogorzalek Loo RR, Lakshmanan R, Loo JA. What protein charging (and supercharging) reveal about the mechanism of electrospray ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1675-93. [PMID: 25135609 PMCID: PMC4163133 DOI: 10.1007/s13361-014-0965-1] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 06/13/2014] [Accepted: 07/08/2014] [Indexed: 05/11/2023]
Abstract
Understanding the charging mechanism of electrospray ionization is central to overcoming shortcomings such as ion suppression or limited dynamic range, and explaining phenomena such as supercharging. Towards that end, we explore what accumulated observations reveal about the mechanism of electrospray. We introduce the idea of an intermediate region for electrospray ionization (and other ionization methods) to account for the facts that solution charge state distributions (CSDs) do not correlate with those observed by ESI-MS (the latter bear more charge) and that gas phase reactions can reduce, but not increase, the extent of charging. This region incorporates properties (e.g., basicities) intermediate between solution and gas phase. Assuming that droplet species polarize within the high electric field leads to equations describing ion emission resembling those from the equilibrium partitioning model. The equations predict many trends successfully, including CSD shifts to higher m/z for concentrated analytes and shifts to lower m/z for sprays employing smaller emitter opening diameters. From this view, a single mechanism can be formulated to explain how reagents that promote analyte charging ("supercharging") such as m-NBA, sulfolane, and 3-nitrobenzonitrile increase analyte charge from "denaturing" and "native" solvent systems. It is suggested that additives' Brønsted basicities are inversely correlated to their ability to shift CSDs to lower m/z in positive ESI, as are Brønsted acidities for negative ESI. Because supercharging agents reduce an analyte's solution ionization, excess spray charge is bestowed on evaporating ions carrying fewer opposing charges. Brønsted basicity (or acidity) determines how much ESI charge is lost to the agent (unavailable to evaporating analyte).
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Affiliation(s)
- Rachel R Ogorzalek Loo
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, University of California-Los Angeles, Los Angeles, CA, 90095, USA,
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40
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Yue X, Vahidi S, Konermann L. Insights into the mechanism of protein electrospray ionization from salt adduction measurements. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1322-1331. [PMID: 24839193 DOI: 10.1007/s13361-014-0905-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 04/03/2014] [Indexed: 06/03/2023]
Abstract
The mechanisms whereby protein ions are liberated from charged droplets during electrospray ionization (ESI) remain under investigation. Compact conformers electrosprayed from aqueous solution in positive ion mode likely follow the charged residue model (CRM), which envisions analyte release after solvent evaporation to dryness. The concentration of nonvolatile salts such as NaCl increases sharply within vanishing CRM droplets, promoting nonspecific pairing of Cl(-) and Na(+) with charged groups on the protein surface. For unfolded proteins, it has been proposed that ion formation occurs via the chain ejection model (CEM). During the CEM proteins are expelled from the droplet long before complete solvent evaporation has taken place. Here we examine whether salt adduction levels support the view that folded and unfolded proteins follow different ESI mechanisms. Solvent evaporation during the CEM is expected to be less extensive and, hence, the salt concentration at the point of protein release should be substantially lower than for the CRM. CEM ions should therefore exhibit lower adduction levels than CRM species. We explore the adduction behavior of several proteins that were chosen to allow comparative studies on folded and unfolded structures in the same solution. In-source activation eliminates chloride adducts via HCl release, generating protein ions that are heterogeneously charged because of sodiation and protonation. Sodiation levels measured under such conditions provide estimates of the salt adduction behavior experienced by the "nascent" analyte ions. Sodiation levels are significantly reduced for unfolded proteins, supporting the view that these species are indeed formed via the CEM.
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Affiliation(s)
- Xuanfeng Yue
- Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
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41
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Chingin K, Xu N, Chen H. Soft supercharging of biomolecular ions in electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:928-934. [PMID: 24733276 DOI: 10.1007/s13361-014-0887-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/08/2014] [Accepted: 03/17/2014] [Indexed: 06/03/2023]
Abstract
The charge states of biomolecular ions in ESI-MS can be significantly increased by the addition of low-vapor supercharging (SC) reagents into the spraying solution. Despite the considerable interest from the community, the mechanistic aspects of SC are not well understood and are hotly debated. Arguments that denaturation accounts for the increased charging observed in proteins sprayed from aqueous solutions containing SC reagent have been published widely, but often with incomplete or ambiguous supporting data. In this work, we explored ESI MS charging and SC behavior of several biopolymers including proteins and DNA oligonucleotides. Analytes were ionized from 100 mM ammonium acetate (NH4Ac) aqueous buffer in both positive (ESI+) and negative (ESI-) ion modes. SC was induced either with m-NBA or by the elevated temperature of ESI capillary. For all the analytes studied we, found striking differences in the ESI MS response to these two modes of activation. The data suggest that activation with m-NBA results in more extensive analyte charging with lower degree of denaturation. When working solution with m-NBA was analyzed at elevated temperatures, the SC effect from m-NBA was neutralized. Instead, the net SC effect was similar to the SC effect achieved by thermal activation only. Overall, our observations indicate that SC reagents enhance ESI charging of biomolecules via distinctly different mechanism compared with the traditional approaches based on analyte denaturation. Instead, the data support the hypothesis that the SC phenomenon involves a direct interaction between a biopolymer and SC reagent occurring in evaporating ESI droplets.
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Affiliation(s)
- Konstantin Chingin
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China Institute of Technology, Nanchang, Jiangxi Province, 330013, China,
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42
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Teo CA, Donald WA. Solution Additives for Supercharging Proteins beyond the Theoretical Maximum Proton-Transfer Limit in Electrospray Ionization Mass Spectrometry. Anal Chem 2014; 86:4455-62. [DOI: 10.1021/ac500304r] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Chen A. Teo
- School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - William A. Donald
- School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
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43
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In-spray supercharging of intact proteins by capillary electrophoresis–electrospray ionization–mass spectrometry using sheath liquid interface. Anal Chim Acta 2014; 813:97-105. [DOI: 10.1016/j.aca.2013.12.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/17/2013] [Accepted: 12/28/2013] [Indexed: 01/10/2023]
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44
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Silveira JA, Fort KL, Kim D, Servage KA, Pierson NA, Clemmer DE, Russell DH. From Solution to the Gas Phase: Stepwise Dehydration and Kinetic Trapping of Substance P Reveals the Origin of Peptide Conformations. J Am Chem Soc 2013; 135:19147-53. [DOI: 10.1021/ja4114193] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Joshua A. Silveira
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Kyle L. Fort
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - DoYong Kim
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Kelly A. Servage
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Nicholas A. Pierson
- Department
of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - David E. Clemmer
- Department
of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - David H. Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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45
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Brahim B, Alves S, Cole RB, Tabet JC. Charge enhancement of single-stranded DNA in negative electrospray ionization using the supercharging reagent meta-nitrobenzyl alcohol. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2013; 24:1988-1996. [PMID: 24030289 DOI: 10.1007/s13361-013-0732-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 07/26/2013] [Accepted: 08/07/2013] [Indexed: 06/02/2023]
Abstract
Charge enhancement of single-stranded oligonucleotide ions in negative ESI mode is investigated. The employed reagent, meta-nitrobenzyl alcohol (m-NBA), was found to improve total signal intensity (Itot), increase the highest observed charge states (zhigh), and raise the average charge states (zavg) of all tested oligonucleotides analyzed in negative ESI. To quantify these increases, signal enhancement ratios (SER1%) and charge enhancement coefficients (CEC1%) were introduced. The SER1%, (defined as the quotient of total oligonucleotide ion abundances with 1% m-NBA divided by total oligonucleotide abundance without m-NBA) was found to be greater than unity for every oligonucleotide tested. The CEC1% values (defined as the average charge state in the presence of 1% m-NBA minus the average charge state in the absence of m-NBA) were found to be uniformly positive. Upon close inspection, the degree of charge enhancement for longer oligonucleotides was found to be dependent upon thymine density (i.e., the number and the location of phospho-thymidine units). A correlation between the charge enhancement induced by the presence of m-NBA and the apparent gas-phase acidity (largely determined by the sequence of thymine units but also by the presence of protons on other nucleobases) of multiply deprotonated oligonucleotide species, was thus established. Ammonium cations appeared to be directly involved in the m-NBA supercharging mechanism, and their role seems to be consistent with previously postulated ESI mechanisms describing desorption/ionization of single-stranded DNA into the gas phase.
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Affiliation(s)
- Bessem Brahim
- Institut Parisien de Chimie Moléculaire, Equipe de Chimie Structurale Organique et Biologique, Université Pierre et Marie Curie, CNRS UMR 7201, 75252, Paris cedex 05, France
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46
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Douglass KA, Venter AR. Predicting the Highest Intensity Ion in Multiple Charging Envelopes Observed for Denatured Proteins during Electrospray Ionization Mass Spectrometry by Inspection of the Amino Acid Sequence. Anal Chem 2013; 85:8212-8. [DOI: 10.1021/ac401245r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Kevin A. Douglass
- Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008-5413, United States
| | - Andre R. Venter
- Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008-5413, United States
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47
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Hall Z, Hernández H, Marsh J, Teichmann S, Robinson C. The role of salt bridges, charge density, and subunit flexibility in determining disassembly routes of protein complexes. Structure 2013; 21:1325-37. [PMID: 23850452 PMCID: PMC3737473 DOI: 10.1016/j.str.2013.06.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 05/16/2013] [Accepted: 06/05/2013] [Indexed: 01/07/2023]
Abstract
Mass spectrometry can be used to characterize multiprotein complexes, defining their subunit stoichiometry and composition following solution disruption and collision-induced dissociation (CID). While CID of protein complexes in the gas phase typically results in the dissociation of unfolded subunits, a second atypical route is possible wherein compact subunits or subcomplexes are ejected without unfolding. Because tertiary structure and subunit interactions may be retained, this is the preferred route for structural investigations. How can we influence which pathway is adopted? By studying properties of a series of homomeric and heteromeric protein complexes and varying their overall charge in solution, we found that low subunit flexibility, higher charge densities, fewer salt bridges, and smaller interfaces are likely to be involved in promoting dissociation routes without unfolding. Manipulating the charge on a protein complex therefore enables us to direct dissociation through structurally informative pathways that mimic those followed in solution.
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Affiliation(s)
- Zoe Hall
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Helena Hernández
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
| | - Joseph A. Marsh
- EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK
| | - Sarah A. Teichmann
- EMBL-European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
| | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, UK
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48
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Yoshimura Y, Habaki H, Egashira R. Separation of Coker Gas Oil by Solvent Extraction. JOURNAL OF CHEMICAL ENGINEERING OF JAPAN 2013. [DOI: 10.1252/jcej.13we048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Yoshihisa Yoshimura
- Department of International Development Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology
| | - Hiroaki Habaki
- Department of International Development Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology
| | - Ryuichi Egashira
- Department of International Development Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology
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49
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Flick TG, Williams ER. Supercharging with trivalent metal ions in native mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1885-95. [PMID: 22948901 PMCID: PMC3474886 DOI: 10.1007/s13361-012-0463-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 07/29/2012] [Accepted: 07/30/2012] [Indexed: 05/11/2023]
Abstract
Addition of 1.0 mM LaCl(3) to aqueous ammonium acetate solutions containing proteins in their folded native forms can result in a significant increase in the molecular ion charging obtained with electrospray ionization as a result of cation adduction. In combination with m-nitrobenzyl alcohol, molecular ion charge states that are greater than the number of basic sites in the protein can be produced from these native solutions, even for lysozyme, which is conformationally constrained by four intramolecular disulfide bonds. Circular dichroism spectroscopy indicates that the conformation of ubiquitin is not measurably affected with up to 1.0 M LaCl(3), but ion mobility data indicate that the high charge states that are formed when 1.0 mM LaCl(3) is present are more unfolded than the low charge states formed without this reagent. These and other results indicate that the increased charging is a result of La(3+) preferentially adducting onto compact or more native-like conformers during ESI and the gas-phase ions subsequently unfolding as a result of increased Coulomb repulsion. Electron capture dissociation of these high charge-state ions formed from these native solutions results in comparable sequence coverage to that obtained for ions formed from denaturing solutions without supercharging reagents, making this method a potentially powerful tool for obtaining structural information in native mass spectrometry.
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Affiliation(s)
- Tawnya G Flick
- Department of Chemistry, University of California-Berkeley, Berkeley, CA 94720-1460, USA
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50
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Li J, Inutan ED, Wang B, Lietz CB, Green DR, Manly CD, Richards AL, Marshall DD, Lingenfelter S, Ren Y, Trimpin S. Matrix assisted ionization: new aromatic and nonaromatic matrix compounds producing multiply charged lipid, peptide, and protein ions in the positive and negative mode observed directly from surfaces. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1625-43. [PMID: 22895857 DOI: 10.1007/s13361-012-0413-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 05/09/2012] [Accepted: 05/11/2012] [Indexed: 05/25/2023]
Abstract
Matrix assisted inlet ionization (MAII) is a method in which a matrix:analyte mixture produces mass spectra nearly identical to electrospray ionization without the application of a voltage or the use of a laser as is required in laserspray ionization (LSI), a subset of MAII. In MAII, the sample is introduced by, for example, tapping particles of dried matrix:analyte into the inlet of the mass spectrometer and, therefore, permits the study of conditions pertinent to the formation of multiply charged ions without the need of absorption at a laser wavelength. Crucial for the production of highly charged ions are desolvation conditions to remove matrix molecules from charged matrix:analyte clusters. Important factors affecting desolvation include heat, vacuum, collisions with gases and surfaces, and even radio frequency fields. Other parameters affecting multiply charged ion production is sample preparation, including pH and solvent composition. Here, findings from over 100 compounds found to produce multiply charged analyte ions using MAII with the inlet tube set at 450 °C are presented. Of the compounds tested, many have -OH or -NH(2) functionality, but several have neither (e.g., anthracene), nor aromaticity or conjugation. Binary matrices are shown to be applicable for LSI and solvent-free sample preparation can be applied to solubility restricted compounds, and matrix compounds too volatile to allow drying from common solvents. Our findings suggest that the physical properties of the matrix such as its morphology after evaporation of the solvent, its propensity to evaporate/sublime, and its acidity are more important than its structure and functional groups.
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Affiliation(s)
- Jing Li
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
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