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Khalikova M, Jireš J, Horáček O, Douša M, Kučera R, Nováková L. What is the role of current mass spectrometry in pharmaceutical analysis? MASS SPECTROMETRY REVIEWS 2024; 43:560-609. [PMID: 37503656 DOI: 10.1002/mas.21858] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 06/02/2023] [Accepted: 06/25/2023] [Indexed: 07/29/2023]
Abstract
The role of mass spectrometry (MS) has become more important in most application domains in recent years. Pharmaceutical analysis is specific due to its stringent regulation procedures, the need for good laboratory/manufacturing practices, and a large number of routine quality control analyses to be carried out. The role of MS is, therefore, very different throughout the whole drug development cycle. While it dominates within the drug discovery and development phase, in routine quality control, the role of MS is minor and indispensable only for selected applications. Moreover, its role is very different in the case of analysis of small molecule pharmaceuticals and biopharmaceuticals. Our review explains the role of current MS in the analysis of both small-molecule chemical drugs and biopharmaceuticals. Important features of MS-based technologies being implemented, method requirements, and related challenges are discussed. The differences in analytical procedures for small molecule pharmaceuticals and biopharmaceuticals are pointed out. While a single method or a small set of methods is usually sufficient for quality control in the case of small molecule pharmaceuticals and MS is often not indispensable, a large panel of methods including extensive use of MS must be used for quality control of biopharmaceuticals. Finally, expected development and future trends are outlined.
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Affiliation(s)
- Maria Khalikova
- Department of Analytical Chemistry, Faculty of Pharmacy in Hradec Králové, Charles University, Hradec Králové, Czech Republic
- Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové, Czech Republic
| | - Jakub Jireš
- Department of Analytical Chemistry, Faculty of Chemical Engineering, UCT Prague, Prague, Czech Republic
- Department of Development, Zentiva, k. s., Praha, Praha, Czech Republic
| | - Ondřej Horáček
- Department of Pharmaceutical Chemistry and Pharmaceutical Analysis, Faculty of Pharmacy in Hradec Králové, Charles University, Hradec Králové, Czech Republic
| | - Michal Douša
- Department of Development, Zentiva, k. s., Praha, Praha, Czech Republic
| | - Radim Kučera
- Department of Pharmaceutical Chemistry and Pharmaceutical Analysis, Faculty of Pharmacy in Hradec Králové, Charles University, Hradec Králové, Czech Republic
| | - Lucie Nováková
- Department of Analytical Chemistry, Faculty of Pharmacy in Hradec Králové, Charles University, Hradec Králové, Czech Republic
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2
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Shi J, Phipps WS, Owusu BY, Henderson CM, Laha TJ, Becker JO, Razavi M, Emrick MA, Hoofnagle AN. A distributable LC-MS/MS method for the measurement of serum thyroglobulin. J Mass Spectrom Adv Clin Lab 2022; 26:28-33. [PMID: 36388059 PMCID: PMC9641599 DOI: 10.1016/j.jmsacl.2022.09.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 09/11/2022] [Accepted: 09/14/2022] [Indexed: 11/19/2022] Open
Abstract
Background Despite its clear advantages over immunoassay-based testing, the measurement of serum thyroglobulin by mass spectrometry remains limited to a handful of institutions. Slow adoption by clinical laboratories could reflect limited accessibility to existing methods that have sensitivity comparable to modern immunoassays, as well as a lack of tools for calibration and assay harmonization. Methods We developed and validated a liquid chromatography-tandem mass spectrometry-based assay for the quantification of serum thyroglobulin. The protocol combined peptide immunoaffinity purification using a commercially available, well-characterized monoclonal antibody and mobile phase modification with dimethylsulfoxide (DMSO) for enhanced sensitivity. To facilitate harmonization with other laboratories, we developed a novel, serum-based 5-point distributable reference material (Husky Ref). Results The assay demonstrated a lower limit of quantification of 0.15 ng/mL (<20 %CV). Mobile phase DMSO increased signal intensity of the target peptide at least 3-fold, improving quantification at low concentrations. Calibration traceable to Husky Ref enabled harmonization between laboratories in an interlaboratory study. Conclusions Sensitive mass spectrometry-based thyroglobulin measurement can be achieved using a monoclonal antibody during peptide immunoaffinity purification and the addition of mobile phase DMSO. Laboratories interested in deploying this assay can utilize the provided standard operating procedure and freely-available Husky Ref reference material.
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Affiliation(s)
- Junyan Shi
- Departments of Laboratory Medicine and Pathology, USA
| | | | | | | | | | | | | | | | - Andrew N. Hoofnagle
- Departments of Laboratory Medicine and Pathology, USA
- Medicine, University of Washington School of Medicine, Seattle, WA, USA
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3
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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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4
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Evaluation of strategies for overcoming trifluoroacetic acid ionization suppression resulted in single-column intact level, middle-up, and bottom-up reversed-phase LC-MS analyses of antibody biopharmaceuticals. Talanta 2021; 233:122512. [PMID: 34215127 DOI: 10.1016/j.talanta.2021.122512] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 05/07/2021] [Accepted: 05/08/2021] [Indexed: 11/22/2022]
Abstract
A wide range of strategies for efficient chromatography and high MS sensitivity in reversed-phase LC-MS analysis of antibody biopharmaceuticals and their large derivates has been evaluated. They included replacing trifluoroacetic acid with alternative acidifiers, relevancy of elevated column temperature, use of dedicated stationary phases, and counteraction of the suppression effect of trifluoroacetic acid in electrospray ionization. At the column temperature of 60 °C, which significantly reduces in-column protein degradation, the BioResolve RP mAb Polyphenyl, BioShell IgG C4 columns performed best using mobile phases with full or partial replacement of trifluoroacetic acid with difluoroacetic acid in the analysis of intact antibodies. Similarly, 0.03% trifluoroacetic acid in combination with 0.07% formic acid is a good alternative in analyzing antibody chains at 60 °C. Collectively, the addition of 3% 1-butanol to the mobile phase acidified with 0.1% formic acid was the most efficient approach to simultaneously achieving good chromatographic separation and MS sensitivity for intact and reduced antibody biopharmaceuticals. Moreover, this mobile phase combined with the BioResolve RP mAb Polyphenyl column was subsequently demonstrated to provide excellent results for peptide mapping of antibody biopharmaceuticals fully comparable with those obtained using a state-of-the-art column for peptide separation, thus opening an avenue for a single-column multilevel analysis of these biotherapeutics.
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5
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Lermyte F, Theisen A, O'Connor PB. Solution Condition-Dependent Formation of Gas-Phase Protomers of Alpha-Synuclein in Electrospray Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:364-372. [PMID: 33237779 DOI: 10.1021/jasms.0c00373] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
One of the main characteristics of biomolecular ions in mass spectrometry is their net charge, and a range of approaches exist to either increase or decrease this quantity in the gas phase. In the context of small molecules, it is well known that, in addition to the charge state, the charge site also has a profound effect on an ion's gas-phase behavior; however, this effect has been far less explored for peptides and intact proteins. Methods exist to determine charge sites of protein ions, and others have observed that the interplay of electrostatic repulsion and inherent basicity leads to different sites gaining or losing a charge depending on the total net charge. Here, we report two distinct protonation site isomers ("protomers") of α-synuclein occurring at the same charge state. The protomers showed important differences in their gas-phase fragmentation behavior and were furthermore distinguishable by ion mobility spectrometry. One protomer was produced under standard electrospray conditions, while the other was observed after addition of 10% dimethyl sulfoxide to the protein solution. Charge sites for both protomers were determined using ultraviolet photodissociation.
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Affiliation(s)
- Frederik Lermyte
- Department of Chemistry, Technical University of Darmstadt, 64287 Darmstadt, Germany
- School of Engineering, University of Warwick, Coventry CV4 7AL, U.K
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Alina Theisen
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
| | - Peter B O'Connor
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K
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6
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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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7
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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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8
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Assessing mixtures of supercharging agents to increase the abundance of a specific charge state of Neuromedin U. Talanta 2019; 198:206-214. [PMID: 30876551 DOI: 10.1016/j.talanta.2019.01.098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 11/24/2022]
Abstract
With increasing evidence of the important role of peptides in pathophysiological processes, a trend towards the development of highly sensitive bioanalytical methods is ongoing. Inherent to the electrospray ionization process of peptides and proteins is the production of multiple charge states which may hamper proper and sensitive method development. Supercharging agents allow modifying the maximal charge state and the corresponding distribution of charges, thereby potentially increasing the number of ions reaching the detector in selected reaction monitoring mode. In this study, the use of mixtures of charge state modifying additives, i.e. m-nitrobenzylalcohol (mNBA), sulfolane and dimethyl sulfoxide (DMSO), to specifically increase the abundance of one charge state of interest has been investigated. Screening experiments were performed to define an experimental domain, which was then further investigated via a response surface design to predict the optimal combination and concentration of superchargers. Using a combination of mNBA and DMSO (0.008% and 0.5% m/v respectively), we were able to increase the abundance of the +4 charge state of the investigated peptide neuromedin U from 64% to 87%. Unfortunately, charge state coalescence did not result in repeatable sensitivity improvements in this case study. However, it remains an attractive approach during method development of peptide bioanalytical methods, as coalescence to a particular intermediate charge state is difficult to obtain by using only one supercharging agent.
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9
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Asare SO, Lynn BC. A comparative study of the electrospray ionization response of β-O-4' lignin model compounds. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:540-548. [PMID: 31009548 DOI: 10.1002/jms.4365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 03/14/2019] [Accepted: 04/11/2019] [Indexed: 06/09/2023]
Abstract
Electrospray ionization mass spectrometry has recently become the technique of choice for rapid characterization of lignin degradation products. However, the fundamental question of the relationship between lignin structure and ionization efficiency has not been explored. In this work, we studied the electrospray ionization response of five structurally similar β-O-4' model lignin compounds using lithium cationization in the positive electrospray ionization mode. The studied compounds have the same β-O-4' backbone structure but differ at the α-position by increasing nonpolar side chains. Our results show a correlation between the ionization response and the length of the nonpolar side chain, with analytes having the longest side chain recording the highest ESI response in the full scan mode. Factors affecting the formation of analyte ions and analyte cluster ions were also studied. We have shown for the first time in this work that the introduction of a nonpolar group onto a β-O-4' lignin compound can increase the lithium cationization ESI response in the positive ion mode.
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Affiliation(s)
- Shardrack O Asare
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
| | - Bert C Lynn
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
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10
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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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11
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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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12
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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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13
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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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14
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Judák P, Van Eenoo P, Deventer K. Urinary matrix effects in electrospray ionization mass spectrometry in the presence of DMSO. JOURNAL OF MASS SPECTROMETRY : JMS 2018; 53:1018-1021. [PMID: 29952038 DOI: 10.1002/jms.4255] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/13/2018] [Accepted: 06/19/2018] [Indexed: 06/08/2023]
Affiliation(s)
- Péter Judák
- Department of Clinical Chemistry, Microbiology and Immunology, Doping Control Laboratory, Ghent University, Zwijnaarde, Belgium
| | - Peter Van Eenoo
- Department of Clinical Chemistry, Microbiology and Immunology, Doping Control Laboratory, Ghent University, Zwijnaarde, Belgium
| | - Koen Deventer
- Department of Clinical Chemistry, Microbiology and Immunology, Doping Control Laboratory, Ghent University, Zwijnaarde, Belgium
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15
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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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16
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Qu M, An B, Shen S, Zhang M, Shen X, Duan X, Balthasar JP, Qu J. Qualitative and quantitative characterization of protein biotherapeutics with liquid chromatography mass spectrometry. MASS SPECTROMETRY REVIEWS 2017; 36:734-754. [PMID: 27097288 DOI: 10.1002/mas.21500] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 03/02/2016] [Indexed: 06/05/2023]
Abstract
In the last decade, the advancement of liquid chromatography mass spectrometry (LC/MS) techniques has enabled their broad application in protein characterization, both quantitatively and qualitatively. Owing to certain important merits of LC/MS techniques (e.g., high selectivity, flexibility, and rapid method development), LC/MS assays are often deemed as preferable alternatives to conventional methods (e.g., ligand-binding assays) for the analysis of protein biotherapeutics. At the discovery and development stages, LC/MS is generally employed for two purposes absolute quantification of protein biotherapeutics in biological samples and qualitative characterization of proteins. For absolute quantification of a target protein in bio-matrices, recent work has led to improvements in the efficiency of LC/MS method development, sample treatment, enrichment and digestion, and high-performance low-flow-LC separation. These advances have enhanced analytical sensitivity, specificity, and robustness. As to qualitative analysis, a range of techniques have been developed to characterize intramolecular disulfide bonds, glycosylation, charge variants, primary sequence heterogeneity, and the drug-to-antibody ratio of antibody drug conjugate (ADC), which has enabled a refined ability to assess product quality. In this review, we will focus on the discussion of technical challenges and strategies of LC/MS-based quantification and characterization of biotherapeutics, with the emphasis on the analysis of antibody-based biotherapeutics such as monoclonal antibodies (mAbs) and ADCs. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 36:734-754, 2017.
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Affiliation(s)
- Miao Qu
- Beijing University of Chinese Medicine, Beijing, 100029, China
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
| | - Bo An
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
| | - Shichen Shen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
| | - Ming Zhang
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
| | - Xiaomeng Shen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
| | - Xiaotao Duan
- State Key Laboratory of Toxicology and Medical Countermeasures, Beijing Institute of Pharmacology and Toxicology, Beijing, 100850, China
| | - Joseph P Balthasar
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
| | - Jun Qu
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, State University of New York, Buffalo, NY, 14214
- New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY, 14203
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17
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Dada OO, Zhao Y, Jaya N, Salas-Solano O. High-Resolution Capillary Zone Electrophoresis with Mass Spectrometry Peptide Mapping of Therapeutic Proteins: Improved Separation with Mixed Aqueous–Aprotic Dipolar Solvents (N,N-Dimethylacetamide and N,N-Dimethylformamide) as the Background Electrolyte. Anal Chem 2017; 89:11227-11235. [DOI: 10.1021/acs.analchem.7b03405] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Oluwatosin O. Dada
- Department of Analytical
Sciences, Seattle Genetics, Inc., 21823 30th Drive SE, Bothell, Washington 98021, United States
| | - Yimeng Zhao
- Department of Analytical
Sciences, Seattle Genetics, Inc., 21823 30th Drive SE, Bothell, Washington 98021, United States
| | - Nomalie Jaya
- Department of Analytical
Sciences, Seattle Genetics, Inc., 21823 30th Drive SE, Bothell, Washington 98021, United States
| | - Oscar Salas-Solano
- Department of Analytical
Sciences, Seattle Genetics, Inc., 21823 30th Drive SE, Bothell, Washington 98021, United States
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18
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Wang L, Rubadue KJ, Alberts J, Bedwell DW, Ruterbories KJ. Development of a rapid and sensitive multiple reaction monitoring proteomic approach for quantification of transporters in human liver tissue. J Chromatogr B Analyt Technol Biomed Life Sci 2017; 1061-1062:356-363. [PMID: 28800539 DOI: 10.1016/j.jchromb.2017.07.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/09/2017] [Accepted: 07/28/2017] [Indexed: 01/23/2023]
Abstract
With increasing knowledge on the role of hepatic transporters in drug disposition, numerous efforts have been described to quantify the expression of human hepatic transporters. However, reported quantitative proteomic approaches often require long analysis times. Additionally, greater assay sensitivity is still necessary for less abundant transporters or limited quantity of samples (e.g. hepatocytes and liver tissue). In the present study, an LC-MS/MS method for rapid and simultaneous quantification of 12 hepatic transporters (BCRP, BSEP, MATE1, MRP2, MRP3, MRP4, NTCP, OATP1B1, 1B3, 2B1, OCT1, and P-gp) was developed. Using a high LC flow rate (1.5mL/min) and fast LC gradient (4min total cycle time), the run time was markedly reduced to 4min, which was much shorter than most previously published assays. Chromatographic separation was achieved using ACE UltraCore SuperC18 50mm×2.1mm 5-μm HPLC column. In addition, greater analytical sensitivity was achieved with both high LC flow rate/fast LC gradient and post-column infusion of ethylene glycol. The on-column LLOQ for signature peptides in this method ranged from 0.194 to 0.846 femtomoles. The impact of five protein solubilizers, including extraction buffer II of ProteoExtract Native Membrane Protein Extraction Kit, 3% (w/v) sodium deoxycholate, 20% (v/v) Invitrosol, 0.2% (w/v) RapiGest SF, and 10% (w/v) formamide on total membrane protein extraction and trypsin digestion was investigated. Sodium deoxycholate was chosen because of good total membrane protein extraction and trypsin digestion efficiency, as well as no significant MS interference. Good precision (within 15% coefficient of variation) and accuracy (within ±15% bias), and inter-day trypsin digestion efficiency (within 28% coefficient of variation) was observed for quality controls. This method can quantify human hepatic transporter expression in a high-throughput manner and due to the increased sensitivity can be used to investigate the down-regulation of hepatic transporter protein (e.g., different ethnic groups and liver disease patients).
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Affiliation(s)
- Li Wang
- Drug Disposition, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States.
| | - Kasi J Rubadue
- Advanced Testing Laboratory, Cincinnati, OH, United States
| | - Jeffrey Alberts
- Drug Disposition, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - David W Bedwell
- Drug Disposition, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
| | - Kenneth J Ruterbories
- Drug Disposition, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, United States
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19
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Donor MT, Ewing SA, Zenaidee MA, Donald WA, Prell JS. Extended Protein Ions Are Formed by the Chain Ejection Model in Chemical Supercharging Electrospray Ionization. Anal Chem 2017; 89:5107-5114. [DOI: 10.1021/acs.analchem.7b00673] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Micah T. Donor
- Department
of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Simon A. Ewing
- Department
of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Muhammad A. Zenaidee
- 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
| | - James S. Prell
- Department
of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
- Materials
Science Institute, University of Oregon, Eugene, Oregon 97403-1252, United States
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20
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E. Nazari Z, van de Weert M, Bou-Assaf G, Houde D, Weiskopf A, D. Rand K. Rapid Conformational Analysis of Protein Drugs in Formulation by Hydrogen/Deuterium Exchange Mass Spectrometry. J Pharm Sci 2016; 105:3269-3277. [DOI: 10.1016/j.xphs.2016.07.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Revised: 06/29/2016] [Accepted: 07/12/2016] [Indexed: 01/21/2023]
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21
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Mortensen DN, Williams ER. Surface-Induced Protein Unfolding in Submicron Electrospray Emitters. Anal Chem 2016; 88:9662-9668. [PMID: 27615434 DOI: 10.1021/acs.analchem.6b02499] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The charging of protein ions formed by nanoelectrospray ionization (nanoESI) with tips that are between 1.5 μm and 250 nm in outer diameter is compared. More charging is obtained with the smaller tip sizes for proteins that have a net positive charge in solution, and additional high-charge-state distributions are often observed. A single charge-state distribution of holo-myoglobin ions is produced by nanoESI from a slightly acidified aqueous solution with the micron outer diameter tips, but some apo-myoglobin ions are produced with the submicron tips. In contrast, the charge-state distributions for proteins with a net negative charge in solution do not depend on tip size. Both the formation of high charge states and the appearance of higher-charge-state distributions, as well as the loss of the heme group from myoglobin, indicate that a fraction of the protein population is unfolding with the smaller tips. The increased charging with the smaller tip sizes for proteins with a net positive charge but not for proteins with a net negative charge indicates that the unfolding occurs prior to nanoelectrospray ionization as a result of Coulombic attraction between positively charged protein molecules in solution and the glass surfaces of the emitter tips that are negatively charged. These results demonstrate a novel method for producing highly charged protein ions that does not require exposing the proteins to additional chemicals either in solution or in the gas phase.
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Affiliation(s)
- Daniel N Mortensen
- Department of Chemistry, University of California , Berkeley, California 94720-1460, United States
| | - Evan R Williams
- Department of Chemistry, University of California , Berkeley, California 94720-1460, United States
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22
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Comparative studies of peak intensities and chromatographic separation of proteolytic digests, PTMs, and intact proteins obtained by nanoLC-ESI MS analysis at room and elevated temperatures. Anal Bioanal Chem 2016; 408:3953-68. [DOI: 10.1007/s00216-016-9386-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 01/26/2016] [Accepted: 02/01/2016] [Indexed: 12/26/2022]
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23
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Patrie SM. Top-Down Mass Spectrometry: Proteomics to Proteoforms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 919:171-200. [PMID: 27975217 DOI: 10.1007/978-3-319-41448-5_8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This chapter highlights many of the fundamental concepts and technologies in the field of top-down mass spectrometry (TDMS), and provides numerous examples of contributions that TD is making in biology, biophysics, and clinical investigations. TD workflows include variegated steps that may include non-specific or targeted preparative strategies, orthogonal liquid chromatography techniques, analyte ionization, mass analysis, tandem mass spectrometry (MS/MS) and informatics procedures. This diversity of experimental designs has evolved to manage the large dynamic range of protein expression and diverse physiochemical properties of proteins in proteome investigations, tackle proteoform microheterogeneity, as well as determine structure and composition of gas-phase proteins and protein assemblies.
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Affiliation(s)
- Steven M Patrie
- Computational and Systems Biology & Biomedical Engineering Graduate Programs, University of Texas Southwestern Medical Center, Dallas, TX, USA. .,Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX, USA. .,Department of Bioengineering, University of Texas at Dallas, Richardson, TX, USA.
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24
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Sinz A, Arlt C, Chorev D, Sharon M. Chemical cross-linking and native mass spectrometry: A fruitful combination for structural biology. Protein Sci 2015; 24:1193-209. [PMID: 25970732 PMCID: PMC4534171 DOI: 10.1002/pro.2696] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 04/14/2015] [Accepted: 04/29/2015] [Indexed: 12/31/2022]
Abstract
Mass spectrometry (MS) is becoming increasingly popular in the field of structural biology for analyzing protein three-dimensional-structures and for mapping protein-protein interactions. In this review, the specific contributions of chemical crosslinking and native MS are outlined to reveal the structural features of proteins and protein assemblies. Both strategies are illustrated based on the examples of the tetrameric tumor suppressor protein p53 and multisubunit vinculin-Arp2/3 hybrid complexes. We describe the distinct advantages and limitations of each technique and highlight synergistic effects when both techniques are combined. Integrating both methods is especially useful for characterizing large protein assemblies and for capturing transient interactions. We also point out the future directions we foresee for a combination of in vivo crosslinking and native MS for structural investigation of intact protein assemblies.
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Affiliation(s)
- Andrea Sinz
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin-Luther University Halle-WittenbergD-06120, Halle, Germany
| | - Christian Arlt
- Department of Pharmaceutical Chemistry & Bioanalytics, Institute of Pharmacy, Martin-Luther University Halle-WittenbergD-06120, Halle, Germany
| | - Dror Chorev
- Department of Biological Chemistry, Weizmann Institute of ScienceRehovot, 76100, Israel
| | - Michal Sharon
- Department of Biological Chemistry, Weizmann Institute of ScienceRehovot, 76100, Israel
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25
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Targeted LC-MS quantification of intact TAT-fusion therapeutics: a case study. Bioanalysis 2015; 7:981-90. [DOI: 10.4155/bio.15.17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Background: While HIV-1 TAT peptide-conjugation shows great promise on improving intracellular delivery of biotherapeutics in vitro and in vivo, quantification of TAT-fusion therapeutics in biological matrices represents a daunting challenge. Materials & methods: A sensitive MS approach for accurate quantification of intact TAT-fusion protein/polypeptide in plasma was developed. i) A semi-automated 96-well ion-exchange solid phase extraction was developed; ii) a rapid LC separation on C4 was devised; iii) a TAT-fusion analog was constructed as internal standard. Results: We reported that low percentage of supercharging reagents enabled a significant sensitivity improvement of MS for intact TAT-fusion protein/polypeptide analysis. We showed a proof of concept by successfully developing a sensitive LC/MRM-MS method for quantifying GAP161, a TAT-conjugating RasGAP mimics, in rat plasma. Conclusion: This work represents the first quantification of TAT-fusion therapeutics in biological samples by an LC-MS based method.
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26
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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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27
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Lyon YA, Julian RR. Photolytic determination of charge state for large proteins and fragments in an ion trap mass spectrometer. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2015; 29:322-326. [PMID: 26406343 DOI: 10.1002/rcm.7109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 11/06/2014] [Accepted: 11/29/2014] [Indexed: 06/05/2023]
Abstract
RATIONALE One of the major shortcomings of linear ion trap mass spectrometers is poor resolution. Failure to resolve isotopic peaks makes charge state determination for large proteins very difficult, hindering the ability to perform top-down proteomics. METHODS Peptides, proteins and corresponding fragments modified with para-iodobenzoate were trapped and irradiated with 266 nm light from an Nd:YAG laser. Loss of iodine due to photodissociation was then used to assign charge states by measuring the corresponding m/z shifts. RESULTS Initial experiments on small peptides illustrate the feasibility of the method. Further studies performed on larger proteins in higher charge states yielded similar results, revealing that fragment ions over a significant mass range either remain in or are quickly cooled to the laser overlap region of the ion trap. CONCLUSIONS Rapid charge state assignment for both whole molecules and collision-induced dissociation (CID) fragments can be obtained by photoactivation of chromophores with labile carbon-iodine bonds.
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Affiliation(s)
- Yana A Lyon
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA
| | - Ryan R Julian
- Department of Chemistry, University of California, Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA
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28
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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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29
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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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30
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Zhao X, Kang L, Zhang T, Chen J, Ren X, Bao Y, Cheng Y. Rapid quantification of a chemically synthesized peptide GAP162 in rat plasma by liquid chromatography/triple quadrupole tandem mass spectrometry and application to a pharmacokinetic study. RSC Adv 2015. [DOI: 10.1039/c5ra05188f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Liquid chromatography/tandem mass spectrometry (LC-MS/MS) is a promising analytical platform for the quantification of therapeutic peptide in biological fluids for pharmacokinetics (PK) studies.
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Affiliation(s)
- Xiaoping Zhao
- State Key Laboratory of Pathogen and Biosecurity
- Beijing Institute of Microbiology and Epidemiology
- Beijing
- China
| | - Liping Kang
- State Key Laboratory Breeding Base of Dao-di Herbs
- National Resource Center of Chinese Materia Medica
- China Academy of Chinese Medical Sciences
- Beijing
- China
| | | | | | - Xinyi Ren
- State Key Laboratory of Pathogen and Biosecurity
- Beijing Institute of Microbiology and Epidemiology
- Beijing
- China
| | - Yuanwu Bao
- DMPK Department
- BioDuro (Shanghai) Inc
- Shanghai
- China
| | - Yuanguo Cheng
- State Key Laboratory of Pathogen and Biosecurity
- Beijing Institute of Microbiology and Epidemiology
- Beijing
- China
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31
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Gregorich ZR, Ge Y. Top-down proteomics in health and disease: challenges and opportunities. Proteomics 2014; 14:1195-210. [PMID: 24723472 DOI: 10.1002/pmic.201300432] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 03/10/2014] [Accepted: 03/24/2014] [Indexed: 01/06/2023]
Abstract
Proteomics is essential for deciphering how molecules interact as a system and for understanding the functions of cellular systems in human disease; however, the unique characteristics of the human proteome, which include a high dynamic range of protein expression and extreme complexity due to a plethora of PTMs and sequence variations, make such analyses challenging. An emerging "top-down" MS-based proteomics approach, which provides a "bird's eye" view of all proteoforms, has unique advantages for the assessment of PTMs and sequence variations. Recently, a number of studies have showcased the potential of top-down proteomics for the unraveling of disease mechanisms and discovery of new biomarkers. Nevertheless, the top-down approach still faces significant challenges in terms of protein solubility, separation, and the detection of large intact proteins, as well as underdeveloped data analysis tools. Consequently, new technological developments are urgently needed to advance the field of top-down proteomics. Herein, we intend to provide an overview of the recent applications of top-down proteomics in biomedical research. Moreover, we will outline the challenges and opportunities facing top-down proteomics strategies aimed at understanding and diagnosing human diseases.
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Affiliation(s)
- Zachery R Gregorich
- Molecular and Cellular Pharmacology Training Program, University of Wisconsin-Madison, Madison, WI, USA; Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, USA
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32
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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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33
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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; 25:1675-1693. [PMID: 25135609 DOI: 10.1007/s13361-014-0870-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 06/13/2014] [Accepted: 07/08/2014] [Indexed: 05/25/2023]
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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34
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Xiu L, Valeja SG, Alpert A, Jin S, Ge Y. Effective protein separation by coupling hydrophobic interaction and reverse phase chromatography for top-down proteomics. Anal Chem 2014; 86:7899-906. [PMID: 24968279 PMCID: PMC4144745 DOI: 10.1021/ac501836k] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 06/26/2014] [Indexed: 01/16/2023]
Abstract
One of the challenges in proteomics is the proteome's complexity, which necessitates the fractionation of proteins prior to the mass spectrometry (MS) analysis. Despite recent advances in top-down proteomics, separation of intact proteins remains challenging. Hydrophobic interaction chromatography (HIC) appears to be a promising method that provides high-resolution separation of intact proteins, but unfortunately the salts conventionally used for HIC are incompatible with MS. In this study, we have identified ammonium tartrate as a MS-compatible salt for HIC with comparable separation performance as the conventionally used ammonium sulfate. Furthermore, we found that the selectivity obtained with ammonium tartrate in the HIC mobile phases is orthogonal to that of reverse phase chromatography (RPC). By coupling HIC and RPC as a novel two-dimensional chromatographic method, we have achieved effective high-resolution intact protein separation as demonstrated with standard protein mixtures and a complex cell lysate. Subsequently, the separated intact proteins were identified by high-resolution top-down MS. For the first time, these results have shown the high potential of HIC as a high-resolution protein separation method for top-down proteomics.
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Affiliation(s)
- Lichen Xiu
- Department
of Chemistry, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
| | - Santosh G. Valeja
- Department of Cell and Regenerative Biology, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
| | - Andrew
J. Alpert
- Department of Cell and Regenerative Biology, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
- PolyLC Inc., Columbia 21045, Maryland, United States
| | - Song Jin
- Department
of Chemistry, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
| | - Ying Ge
- Department
of Chemistry, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
- Department of Cell and Regenerative Biology, University of Wisconsin—Madison, Madison 53706, Wisconsin, United States
- Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
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35
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Qiao X, Wang R, Li G, Yan H, Zhou Y, Zhang L, Zhang Y. Imidazolium-based iodoacetamide functional tags: design, synthesis, and property study for cysteinyl-peptide analysis by mass spectrometry. Analyst 2014; 139:705-8. [PMID: 24383064 DOI: 10.1039/c3an01907a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
New types of imidazolium-based iodoacetamide tags were designed, synthesized and further exploited for cysteinyl-peptide analysis with superior labeling efficiency, high stability, improved ionization efficiency, and increased charge states by mass spectrometry. For the first time, the effects of these kinds of tags on the mass spectrometry performance of the derivatized peptides were investigated, which is of great importance to help us design more efficient tags for the analysis of peptides or proteins, especially for those with low abundance.
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Affiliation(s)
- Xiaoqiang Qiao
- Key Laboratory of Medicinal Chemistry and Molecular Diagnosis, Ministry of Education & College of Pharmaceutical Sciences, Hebei University, Baoding 071002, China.
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36
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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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37
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Qiao X, Wang R, Yan H, Wang T, Zhao Q, Zhang L, Zhang Y. Development of a novel imidazolium-based aromatic quaternary ammonium tag: synthesis and application to the efficient analysis of cysteinyl-peptides by mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:256-264. [PMID: 24375876 DOI: 10.1002/rcm.6785] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 10/30/2013] [Accepted: 11/12/2013] [Indexed: 06/03/2023]
Abstract
RATIONALE Chemical derivatization is a very promising technique for improving analysis of peptides by mass spectrometry (MS). In this study, a novel kind of imidazolium-based aromatic quaternary ammonium tag, 1-[3-[(2-iodo-1-oxoethyl)amino]propyl]-3-butylimidazolium bromide (IPBI), designed with strong gas-phase basicity and a permanent positive charge, was firstly synthesized and further used for derivatization of cysteinyl-peptides with improved ionization efficiency and higher charge states. METHODS Both the model peptides and tryptic digests of proteins were used to evaluate the effect of IPBI derivatization on the MS performance of the derivatized peptides, and the results were further compared with the commonly used iodoacetamide (IAA) tag. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-MS and electrospray ionization (ESI)-MS were used to evaluate the ionization efficiency and charge states of the derivatized peptides. RESULTS With model peptides as samples, a nearly 100% derivatization efficiency and superior stability were achieved via IPBI derivatization. By further analysis of both standard peptides and tryptic protein digests, the ionization efficiency and charge states of IPBI-derivatized peptides could be remarkably improved. For example, for protein bovine serum albumin, compared with the commercial available IAA tag, the identification efficiency of cysteinyl-peptides was increased about 67% by combining with IPBI derivatization. CONCLUSIONS The results indicated that the novel tag is an effective derivatization reagent for cysteinyl-peptide identification. We hope it could be further used for high-efficiency cysteinyl-peptide identification in proteome research, especially those with low abundance and poor ionization efficiency.
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Affiliation(s)
- Xiaoqiang Qiao
- Key Laboratory of Pharmaceutical Quality Control of Hebei Province & College of Pharmaceutical Sciences, Hebei University, Baoding, 071002, China
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38
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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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39
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Cho YT, Huang MZ, Wu SY, Hou MF, Li J, Shiea J. Using electrospray laser desorption ionization mass spectrometry to rapidly examine the integrity of proteins stored in various solutions. Anal Bioanal Chem 2013; 406:577-86. [PMID: 24343451 DOI: 10.1007/s00216-013-7491-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 11/05/2013] [Accepted: 11/06/2013] [Indexed: 11/30/2022]
Abstract
Electrospray laser desorption ionization mass spectrometry (ELDI/MS) allows the rapid desorption and ionization of proteins from solutions under ambient conditions. In this study, we have demonstrated the use of ELDI/MS to efficiently examine the integrity of the proteins stored in various solutions before they were further used for other biochemical tests. The protein standards were prepared in the solutions containing buffers, organic salts, inorganic salts, strong acid, strong base, and organic solvents, respectively, to simulate those collected from solvent extraction, filtration, dialysis, or chromatographic separation. Other than the deposit of a drop of the sample solution on the metallic sample plate in an ELDI source, no additional sample pretreatment is needed. The sample drop was then irradiated with a pulsed laser; this led to desorption of the analyte molecules, which subsequently entered the ESI plume to undergo post-ionization. Because adjustment of the composition of the sample solution is unnecessary, this technique appears to be useful for rapidly evaluating the integrity of proteins after storage or prior to further biochemical treatment. In addition, when using acid-free and low-organic-solvent ESI solutions for ELDI/MS analysis, the native conformations of the proteins in solution could be detected.
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Affiliation(s)
- Yi-Tzu Cho
- Department of Cosmetic Applications and Management, Yuh-Ing Junior College of Health Care & Management, No.15 Lane 420 Dachang 2nd Rd, Kaohsiung 807, Taiwan,
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40
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Liu P, Zhang J, Ferguson CN, Chen H, Loo JA. Measuring protein-ligand interactions using liquid sample desorption electrospray ionization mass spectrometry. Anal Chem 2013; 85:11966-72. [PMID: 24237005 PMCID: PMC3901310 DOI: 10.1021/ac402906d] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
We have previously shown that liquid sample desorption electrospray ionization-mass spectrometry (DESI-MS) is able to measure large proteins and noncovalently bound protein complexes (to 150 kDa) (Ferguson et al., Anal. Chem. 2011, 83, 6468-6473). In this study, we further investigate the application of liquid sample DESI-MS to probe protein-ligand interactions. Liquid sample DESI allows the direct formation of intact protein-ligand complex ions by spraying ligands toward separate protein sample solutions. This type of "reactive" DESI methodology can provide rapid information on binding stiochiometry, selectivity, and kinetics, as demonstrated by the binding of ribonuclease A (RNaseA, 13.7 kDa) with cytidine nucleotide ligands and the binding of lysozyme (14.3 kDa) with acetyl chitose ligands. A higher throughput method for ligand screening by liquid sample DESI was demonstrated, in which different ligands were sequentially injected as a segmented flow for DESI ionization. Furthermore, supercharging to enhance analyte charge can be integrated with liquid sample DESI-MS, without interfering with the formation of protein-ligand complexes.
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Affiliation(s)
- Pengyuan Liu
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
| | - Jiang Zhang
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
| | - Carly N. Ferguson
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
| | - Hao Chen
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio 45701, United States
| | - Joseph A. Loo
- Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095, United States
- Department of Biological Chemistry, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California 90095, United States
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41
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Abstract
The peptide hormone glucagon plays an important role in homeostasis of glucose concentrations in the blood. Its biological importance is evidenced through the conservation of its peptide sequence between species. Reliable assays for glucagon in biological samples are important for gaining a better understanding of the pathology and treatment of diabetes. Numerous assays are available for the analysis of glucagon in biological samples, the majority of which employ an immunochemical approach and have been available for many years. However, recent advances in MS instrumentation and the amenability of glucagon for analysis by LC–MS/MS has brought these new methods to the forefront. Concentrations of glucagon determined from different methods are not always consistent and this review provides suggestions of how to improve the reliability of methods for glucagon analysis.
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42
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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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43
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Cubrilovic D, Zenobi R. Influence of dimehylsulfoxide on protein-ligand binding affinities. Anal Chem 2013; 85:2724-30. [PMID: 23347283 DOI: 10.1021/ac303197p] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Because of its favorable physicochemical properties, DMSO is the standard solvent for sample storage and handling of compounds in drug discovery. To date, little attention was given to how DMSO influences protein-ligand binding strengths. In this study we investigated the effects of DMSO on different noncovalent protein-ligand complexes, in particular in terms of the binding affinities, which we determined using nanoESI-MS. For the investigation, three different protein-ligand complexes were chosen: trypsin-Pefabloc, lysozyme-tri-N-acetylchitotriose (NAG3), and carbonic anhydrase-chlorothiazide. The DMSO content in the nanoESI buffer was increased systematically from 0.5 to 8%. For all three model systems, it was shown that the binding affinity decreases upon addition of DMSO. Even 0.5-1% DMSO alters the KD values, in particular for the tight binding system carbonic anhydrase-chlorothiazide. The determined dissociation constant (KD) is up to 10 times higher than for a DMSO-free sample in the case of carbonic anhydrase-chlorothiazide binding. For the trypsin-Pefabloc and lysozyme-NAG3 complexes, the dissociation constants are 7 and 3 times larger, respectively, in the presence of DMSO. This work emphasizes the importance of effects of DMSO as a co-solvent for quantification of protein-ligand binding strengths in the early stages of drug discovery.
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Affiliation(s)
- Dragana Cubrilovic
- Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
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44
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Abstract
Native state mass spectrometry (MS) has been recognised as a rapid, sensitive, and high throughput method to directly investigate protein-ligand interactions for some time, however there are few examples reporting this approach as a screening method to identify relevant protein–fragment interactions in fragment-based drug discovery (FBDD). In this paper an overview of native state MS will be presented, highlighting the attractive properties of this method within the context of fragment screening applications. A summary of published examples using MS for fragment screening will be described and reflection on the outlook for the future adoption and implementation of native state MS as a complementary fragment screening method will be presented.
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45
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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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Fornelli L, Damoc E, Thomas PM, Kelleher NL, Aizikov K, Denisov E, Makarov A, Tsybin YO. Analysis of intact monoclonal antibody IgG1 by electron transfer dissociation Orbitrap FTMS. Mol Cell Proteomics 2012; 11:1758-67. [PMID: 22964222 DOI: 10.1074/mcp.m112.019620] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The primary structural information of proteins employed as biotherapeutics is essential if one wishes to understand their structure-function relationship, as well as in the rational design of new therapeutics and for quality control. Given both the large size (around 150 kDa) and the structural complexity of intact immunoglobulin G (IgG), which includes a variable number of disulfide bridges, its extensive fragmentation and subsequent sequence determination by means of tandem mass spectrometry (MS) are challenging. Here, we applied electron transfer dissociation (ETD), implemented on a hybrid Orbitrap Fourier transform mass spectrometer (FTMS), to analyze a commercial recombinant IgG in a liquid chromatography (LC)-tandem mass spectrometry (MS/MS) top-down experiment. The lack of sensitivity typically observed during the top-down MS of large proteins was addressed by averaging time-domain transients recorded in different LC-MS/MS experiments before performing Fourier transform signal processing. The results demonstrate that an improved signal-to-noise ratio, along with the higher resolution and mass accuracy provided by Orbitrap FTMS (relative to previous applications of top-down ETD-based proteomics on IgG), is essential for comprehensive analysis. Specifically, ETD on Orbitrap FTMS produced about 33% sequence coverage of an intact IgG, signifying an almost 2-fold increase in IgG sequence coverage relative to prior ETD-based analysis of intact monoclonal antibodies of a similar subclass. These results suggest the potential application of the developed methodology to other classes of large proteins and biomolecules.
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Affiliation(s)
- Luca Fornelli
- Biomolecular Mass Spectrometry Laboratory, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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Meyer JG, A Komives E. Charge state coalescence during electrospray ionization improves peptide identification by tandem mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1390-9. [PMID: 22610994 PMCID: PMC6345509 DOI: 10.1007/s13361-012-0404-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 04/25/2012] [Accepted: 04/25/2012] [Indexed: 05/12/2023]
Abstract
We report the effects of supercharging reagents dimethyl sulphoxide (DMSO) and m-nitrobenzyl alcohol (m-NBA) applied to untargeted peptide identification, with special emphasis on non-tryptic peptides. Peptides generated from a mixture of five standard proteins digested with trypsin, elastase, or pepsin were separated with nanoflow liquid chromatography using mobile phases modified with either 5% DMSO or 0.1%m-NBA. Eluting peptides were ionized by online electrospray and sequenced by both CID and ETD using data-dependent MS/MS. Statistically significant improvements in peptide identifications were observed with DMSO co-solvent. In order to understand this observation, we assessed the effects of supercharging reagents on the chromatographic separation and the electrospray quality. The increase in identifications was not due to supercharging, which was greater for the 0.1%m-NBA co-solvent and not observed for the 5.0% DMSO co-solvent. The improved MS/MS efficiency using the DMSO modified mobile phase appeared to result from charge state coalescence.
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Affiliation(s)
- Jesse G Meyer
- Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, CA, 92093-0378, USA
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48
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Halquist MS, Sakagami M, Karnes HT. Determination of oxyntomodulin, an anorectic polypeptide, in rat plasma using 2D-LC-MS/MS coupled with ion pair chromatography. J Chromatogr B Analyt Technol Biomed Life Sci 2012; 903:102-11. [PMID: 22841744 DOI: 10.1016/j.jchromb.2012.06.047] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/18/2012] [Accepted: 06/24/2012] [Indexed: 11/28/2022]
Abstract
Polypeptide therapeutics present a challenge for quantitative analysis when using immunoassays or recently, liquid chromatography-tandem mass spectrometry because of their structural similarities to endogenous proteins and peptides in plasma. In this assay, a Waters Oasis® mixed-mode anion exchange (MAX) microelution modified solid phase extraction (SPE) method coupled with two-dimensional reversed phase ion pair chromatography-tandem mass spectrometry was used for the validation and analysis of oxyntomodulin in rat plasma. Oxyntomodulin (OXM) and its isotope labeled internal standard were extracted from rat plasma and analyzed with a chromatographic run time of 8 min. Modified SPE, two-dimensional liquid chromatography coupled with 3-nitrobenzyl alcohol as a mobile phase additive, and monitoring of multiply charged SRM transitions (+7 charge state) of OXM were necessary to achieve a lower limit of quantification of 1 ng/mL. The method was validated with a linear range of 1-1000 ng/mL, with average R² of 0.992, and reversed calculated residuals between -8.6% and 6.0%. Precision and accuracy for inter- and intra-day were determined to be ±17%. Following a complete validation, the method was applied to show utility using rat plasma samples that were intravenously dosed with oxyntomodulin.
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Affiliation(s)
- Matthew S Halquist
- Department of Pharmaceutics, Virginia Commonwealth University, Richmond, VA 23298, USA
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49
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Liu Y, Miao Z, Lakshmanan R, Ogorzalek Loo RR, Loo JA, Chen H. Signal and Charge Enhancement for Protein Analysis by Liquid Chromatography-Mass Spectrometry with Desorption Electrospray Ionization. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2012; 325-327:161-166. [PMID: 25878557 PMCID: PMC4394628 DOI: 10.1016/j.ijms.2012.06.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We recently reported the use of desorption electrospray ionization (DESI) as a novel interface to couple high-performance liquid chromatography (HPLC) with mass spectrometry (MS) (Chem. Commun. 2011, 47, 4171). One of the benefits of such an interface is that post-column derivatization of separated analytes can be integrated with ionization via a "reactive" DESI approach in which a derivatizing reagent is doped into the spray solvent. The reactive DESI interface allows analyte desorption/ionization from the end of the chromatographic column with prompt MS detection; a short time delay of ~20 ms was demonstrated. In this study, we extended this application by "supercharging" proteins following HPLC separation using a DESI spray solvent containing supercharging reagents, m-nitrobenzyl alcohol (m-NBA) or sulfolane. Proteins (insulin, ubiquitin, lysozyme and α-lactalbumin) eluted out of the LC column can be supercharged with the protein charge state distributions (CSDs) significantly increased (to higher charge), which would be advantageous for subsequent top-down MS analysis of proteins. Interestingly, supercharging combined with reactive DESI enhances tolerance towards trifluoroacetic acid (TFA), which is known to be a superior additive in the mobile phase for premium peptide/protein chromatographic separation but has severe signal suppression effects for conventional electrospray ionization (ESI). In comparison to electrosonic spray ionization (ESSI), a variant form of ESI, the sensitivity of protein analysis using LC/DESI-MS with the mobile phase containing TFA can be improved by up to 70-fold for lysozyme and α-lactalbumin by including m-NBA in the DESI spray solvent. Presumably, by reducing TFA dissociation in the droplet, supercharging agents lower trifluoroacetate anion concentrations and concomitantly reduce ion pairing to analyte cationic sites. The reduced ion pairing therefore decreases the TFA signal suppression effect. The supercharging capability and the reduction of TFA signal suppression suggest that LC/DESI-MS is a valuable method for protein analysis.
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Affiliation(s)
- Yan Liu
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA
| | - Zhixin Miao
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA
| | - Rajeswari Lakshmanan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA
| | - Rachel R Ogorzalek Loo
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, USA ; Department of Biological Chemistry, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA
| | - Hao Chen
- Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Athens, OH, USA
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50
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Miladinović SM, Fornelli L, Lu Y, Piech KM, Girault HH, Tsybin YO. In-spray supercharging of peptides and proteins in electrospray ionization mass spectrometry. Anal Chem 2012; 84:4647-51. [PMID: 22571167 DOI: 10.1021/ac300845n] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Enhanced charging, or supercharging, of analytes in electrospray ionization mass spectrometry (ESI MS) facilitates high resolution MS by reducing an ion mass-to-charge (m/z) ratio, increasing tandem mass spectrometry (MS/MS) efficiency. ESI MS supercharging is usually achieved by adding a supercharging reagent to the electrospray solution. Addition of these supercharging reagents to the mobile phase in liquid chromatography (LC)-MS/MS increases the average charge of enzymatically derived peptides and improves peptide and protein identification in large-scale bottom-up proteomics applications but disrupts chromatographic separation. Here, we demonstrate the average charge state of selected peptides and proteins increases by introducing the supercharging reagents directly into the ESI Taylor cone (in-spray supercharging) using a dual-sprayer ESI microchip. The results are comparable to those obtained by the addition of supercharging reagents directly into the analyte solution or LC mobile phase. Therefore, supercharging reaction can be accomplished on a time-scale of ion liberation from a droplet in the ESI ion source.
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