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Schwenzer AK, Kruse L, Jooß K, Neusüß C. Capillary electrophoresis-mass spectrometry for protein analyses under native conditions: Current progress and perspectives. Proteomics 2024; 24:e2300135. [PMID: 37312401 DOI: 10.1002/pmic.202300135] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 06/15/2023]
Abstract
Native mass spectrometry is a rapidly emerging technique for fast and sensitive structural analysis of protein constructs, maintaining the protein higher order structure. The coupling with electromigration separation techniques under native conditions enables the characterization of proteoforms and highly complex protein mixtures. In this review, we present an overview of current native CE-MS technology. First, the status of native separation conditions is described for capillary zone electrophoresis (CZE), affinity capillary electrophoresis (ACE), and capillary isoelectric focusing (CIEF), as well as their chip-based formats, including essential parameters such as electrolyte composition and capillary coatings. Further, conditions required for native ESI-MS of (large) protein constructs, including instrumental parameters of QTOF and Orbitrap systems, as well as requirements for native CE-MS interfacing are presented. On this basis, methods and applications of the different modes of native CE-MS are summarized and discussed in the context of biological, medical, and biopharmaceutical questions. Finally, key achievements are highlighted and concluded, while remaining challenges are pointed out.
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Affiliation(s)
| | - Lena Kruse
- Department of Chemistry, Aalen University, Aalen, Germany
| | - Kevin Jooß
- Department of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois, USA
- Division of Bioanalytical Chemistry, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- Centre for Analytical Sciences Amsterdam (CASA), Amsterdam, The Netherlands
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Schlecht J, Stolz A, Hofmann A, Gerstung L, Neusüß C. nanoCEasy: An Easy, Flexible, and Robust Nanoflow Sheath Liquid Capillary Electrophoresis-Mass Spectrometry Interface Based on 3D Printed Parts. Anal Chem 2021; 93:14593-14598. [PMID: 34719920 DOI: 10.1021/acs.analchem.1c03213] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Capillary electrophoresis-mass spectrometry (CE-MS) is a powerful tool in various fields including proteomics, metabolomics, and biopharmaceutical and environmental analysis. Nanoflow sheath liquid (SL) CE-MS interfaces provide sensitive ionization, required in these fields, but are still limited to a few research laboratories as handling is difficult and expertise is necessary. Here, we introduce nanoCEasy, a novel nanoflow SL interface based on 3D printed parts, including our previously reported two capillary approach. The customized plug-and-play design enables the introduction of capillaries and an emitter without any fittings in less than a minute. The transparency of the polymer enables visual inspection of the liquid flow inside the interface. Robust operation was systematically demonstrated regarding the electrospray voltage, the distance between the emitter and MS orifice, the distance between the separation capillary and emitter tip, and different individual emitters of the same type. For the first time, we evaluated the influence of high electroosmotic flow (EOF) separation conditions on a nanoflow SL interface. A high flow from the separation capillary can be outbalanced by increasing the electrospray voltage, leading to an overall increased electrospray flow, which enables stable operation under high-EOF conditions. Overall, the nanoCEasy interface allows easy, sensitive, and robust coupling of CE-MS. We aspire the use of this sensitive, easy-to-use interface in large-scale studies and by nonexperts.
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Affiliation(s)
- Johannes Schlecht
- Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany.,Department of Pharmaceutical and Medicinal Chemistry, Friedrich Schiller University Jena, 07743 Jena, Germany
| | - Alexander Stolz
- Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany.,Department of Pharmaceutical and Medicinal Chemistry, Friedrich Schiller University Jena, 07743 Jena, Germany
| | - Adrian Hofmann
- Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany
| | - Lukas Gerstung
- Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany
| | - Christian Neusüß
- Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany
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Investigating the position of the separation capillary and emitter tube tips in a nanoflow sheath-liquid CE-ESI-MS interface to decouple the ESI potential. Talanta 2021; 228:122212. [PMID: 33773698 DOI: 10.1016/j.talanta.2021.122212] [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: 10/29/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 12/11/2022]
Abstract
Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is very important for the high performance of the CE-ESI-MS devices and their applications for highly sensitive analyses of ionogenic compounds. In this study, we utilize a nanoflow sheath-liquid CE-ESI-MS interface composed of a quartz emitter and a separation fused silica capillary treated by etching, which are threaded to cross coupling for sheath liquid and electrode connection. Specifically, we have tested the ability of the interface to decouple the ESI potential from the separation potential at different positions of the separation capillary and ESI emitter tube tips. The interface with the separation capillary tip protruding the emitter tip by 20 μm did not provide sufficient robustness. The real ESI potential (delivered as 2.0 kV from the independent high voltage power supply HV2) ranged from 2.1 kV to 4.5 kV depending on the applied separation voltage (12.0-20.0 kV, provided by the power supply HV1) and electric conductivity of the background electrolyte (BGE) used. The interface robustness was partially improved when the capillary tip was aligned with the emitter tip. However, the complete decoupling of the spray and separation potentials was achieved only when the capillary tip was retracted 20 μm inside the emitter. In this arrangement, the ESI potential was stable and independent of both the separation potential (voltage) and the BGE conductivity. Moreover, this setting provided better sensitivity for the CE-ESI-MS analysis of selected drugs and benzylpyridinium cations than the setup with the capillary tip aligned with or protruding the emitter tip.
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Höcker O, Knierman M, Meixner J, Neusüß C. Two capillary approach for a multifunctional nanoflow sheath liquid interface for capillary electrophoresis-mass spectrometry. Electrophoresis 2020; 42:369-373. [PMID: 32776368 DOI: 10.1002/elps.202000169] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/23/2020] [Accepted: 08/03/2020] [Indexed: 12/18/2022]
Abstract
CE hyphenated to ESI-MS (CE-ESI-MS) is a well-established technique to analyze charged analytes in complex samples. Although various interfaces for CE-MS coupling are commercially available, the development of alternatives which combine sensitivity, simplicity, and robustness remains a topic of research. In this work, a nanoflow sheath liquid CE-MS interface with two movable capillaries inside a glass emitter is described. The setup enables a separation mode and a conditioning mode to guide the separation capillary effluent either into the electrospray or to the waste, respectively. This enables to exclude parts of the analysis from MS detection and unwanted matrix components reaching the mass spectrometer, comparable to divert valves in LC-MS coupling. Also, this function improves the overall robustness of the system by reduction of particles blocking the emitter. Preconditioning with electrospray interfering substances and even the application of coating materials for every analysis is enabled, even while the separation capillary is built into the interface with running electrospray. The functionality is demonstrated by analyses of heavy matrix bioreactor samples. Overall, this innovation offers a more convenient installation of the interface, improved handling with an extended lifetime of the emitter tips and additional functions compared to previous approaches, while keeping the higher sensitivity of nanoflow CE-MS-coupling.
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Affiliation(s)
- Oliver Höcker
- Department of Chemistry, Aalen University, Aalen, Germany
- Instrumental Analytical Chemistry and Centre for Water and Environmental Research (ZWU), Universitätsstraße, University of Duisburg-Essen, Essen, Germany
| | - Mike Knierman
- Laboratory for Experimental Medicine, Lilly Corporate Center, Eli Lilly and Company, Indianapolis, IN, USA
| | - Jens Meixner
- Agilent Technologies R&D and Marketing GmbH & Co. KG, Hewlett-Packard-Straße 8, Waldbronn, Germany
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5
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Characterization of a nanoflow sheath liquid interface and comparison to a sheath liquid and a sheathless porous-tip interface for CE-ESI-MS in positive and negative ionization. Anal Bioanal Chem 2018; 410:5265-5275. [DOI: 10.1007/s00216-018-1179-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/24/2018] [Accepted: 05/30/2018] [Indexed: 01/22/2023]
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Yin Y, Li G, Guan Y, Huang G. Sheathless interface to match flow rate of capillary electrophoresis with electrospray mass spectrometry using regular-sized capillary. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30 Suppl 1:68-72. [PMID: 27539418 DOI: 10.1002/rcm.7621] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
RATIONALE The flow rate match has been a great challenge when coupling capillary electrophoresis (CE) with electrospray ionization mass spectrometry (ESI-MS). Conventional CE-ESI-MS interfaces used liquid sheath flow, narrowed capillary or additional pressure to meet this requirement; sacrifice of either capillary inner diameter (i.d.) or separation efficiency is often inevitable. Thus, a regular-sized capillary-based sheathless interface would be attractive for flow rate match in CE-MS. METHODS The regular-sized capillary-based CE-MS interface was achieved by coupling CE with induced electrospray ionization (iESI) which was stimulated by the fact that the iESI could both achieve flow rate down to 0.2 μL/min and retain ionization efficiency. The CE-iESI-MS interface was completed with an intact separation capillary, outside the outlet end of which a metal electrode was attached for the application of alternating current (ac) high voltage (HV). RESULTS The feasibility of this CE-iESI-MS interface was demonstrated through the stable total ion chromatograms obtained by continuous CE infusion of tripropylamine with regular-sized capillaries. Tripropylamine and atenolol were separated and detected successfully in phosphate buffer solution (PBS) by CE-iESI-MS using a 50 or 75 μm i.d. capillary. Furthermore, this new interface showed a better signal-to-noise (S/N) of 3 to 7 times enhancement compared with another sheathless CE-ESI-MS interface that using one high voltage for both separation and electrospray when analyzing the mixture of tripropylamine and proline in NH4 OAc buffer. In addition, the reproducibility of this interface gave satisfactory results with relative standard deviation (RSD) in retention time in the range between 1% and 3%. CONCLUSIONS The novel sheathless CE-MS interface introduced here could match conventional electroosmotic flow (EOF) with electrospray which could also preserve the separation efficiency and sensitivity of CE-MS. This newly developed CE-iESI-MS interface was also demonstrated to be effective for different buffers, PBS and NH4 OAc, without any additives such as methanol and acetic acid. Hence, we believe that this sheathless CE-MS interface could be operated with other nonvolatile and volatile buffers. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Yue Yin
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China (USTC), Hefei, 230026, China
| | - Gongyu Li
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China (USTC), Hefei, 230026, China
| | - Yafeng Guan
- Department of Instrumentation and Analytical Chemistry, Key Laboratory of Separation Science for Analytical Chemistry of CAS, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China
| | - Guangming Huang
- Department of Chemistry, School of Chemistry and Materials Science, University of Science and Technology of China (USTC), Hefei, 230026, China
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Bonvin G, Schappler J, Rudaz S. Capillary electrophoresis–electrospray ionization-mass spectrometry interfaces: Fundamental concepts and technical developments. J Chromatogr A 2012; 1267:17-31. [DOI: 10.1016/j.chroma.2012.07.019] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/04/2012] [Accepted: 07/06/2012] [Indexed: 01/24/2023]
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9
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Bonvin G, Veuthey JL, Rudaz S, Schappler J. Evaluation of a sheathless nanospray interface based on a porous tip sprayer for CE-ESI-MS coupling. Electrophoresis 2012; 33:552-62. [DOI: 10.1002/elps.201100461] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Reschke BR, Timperman AT. A study of electrospray ionization emitters with differing geometries with respect to flow rate and electrospray voltage. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:2115-2124. [PMID: 21989703 DOI: 10.1007/s13361-011-0251-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 09/10/2011] [Accepted: 09/13/2011] [Indexed: 05/31/2023]
Abstract
The performance of several electrospray ionization emitters with different orifice inside diameters (i.d.s), geometries, and materials are compared. The sample solution is delivered by pressure driven flow, and the electrospray ionization voltage and flow rate are varied systematically for each emitter investigated, while the signal intensity of a standard is measured. The emitters investigated include a series of emitters with a tapered outside diameters (o.d.) and unaltered i.d.s, a series of emitters with tapered o.d.s and i.d.s, an emitter with a monolithic frit and a tapered o.d., and an emitter fabricated from polypropylene. The results show that for the externally etched emitters, signal was nearly independent of i.d. and better ion utilization was achieved at lower flow rates. Furthermore, emitters with a 50 μm i.d. and an etched o.d. produced about 1.5 times more signal than etched emitters with smaller i.d.s and about 3.5 times more signal than emitters with tapered inner and outer dimensions. Additionally, the work presented here has important implications for applications in which maximizing signal intensity and reducing frictional resistance to flow are necessary. Overall, the work provides an initial assessment of the critical parameters that contribute to maximizing the signal for electrospray ionization sources interfaced with pressure driven flows.
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Affiliation(s)
- Brent R Reschke
- C. Eugene Bennet Department of Chemistry, West Virginia University, Morgantown, WV 26506, USA
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Zhong X, Maxwell EJ, Chen DD. Mass Transport in a Micro Flow-Through Vial of a Junction-at-the-Tip Capillary Electrophoresis-Mass Spectrometry Interface. Anal Chem 2011; 83:4916-23. [DOI: 10.1021/ac200636y] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xuefei Zhong
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada V6T 1Z1
| | - E. Jane Maxwell
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada V6T 1Z1
| | - David D.Y. Chen
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, Canada V6T 1Z1
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12
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Hyphenated Methods. Mass Spectrom (Tokyo) 2011. [DOI: 10.1007/978-3-642-10711-5_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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13
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Wojcik R, Dada OO, Sadilek M, Dovichi NJ. Simplified capillary electrophoresis nanospray sheath-flow interface for high efficiency and sensitive peptide analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:2554-60. [PMID: 20740530 DOI: 10.1002/rcm.4672] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We report a simple nanospray sheath-flow interface for capillary electrophoresis. This interface relies on electrokinetic flow to drive both the separation and the electrospray; no mechanical pump is used for the sheath flow. This system was interfaced with an LCQ mass spectrometer. The best results were observed with a 2-microm diameter emitter tip and a 1-mm spacing between the separation capillary tip and the emitter tip. Under these conditions, mass detection limits (3sigma) of 100 amol were obtained for insulin receptor fragment 1142-1153. The separation efficiency exceeded 200,000 plates for this compound. The relative standard deviation generated during continual infusion of a 50 microM solution of angiotensin II was 2% for the total ion count and 3% for the extracted ion count over a 40-min period. Finally, the interface was also demonstrated for negative ion mode.
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Affiliation(s)
- Roza Wojcik
- Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA
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Maxwell EJ, Zhong X, Zhang H, van Zeijl N, Chen DDY. Decoupling CE and ESI for a more robust interface with MS. Electrophoresis 2010; 31:1130-1137. [DOI: 10.1002/elps.200900517] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Covey TR, Thomson BA, Schneider BB. Atmospheric pressure ion sources. MASS SPECTROMETRY REVIEWS 2009; 28:870-97. [PMID: 19626583 DOI: 10.1002/mas.20246] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This review of atmospheric pressure ion sources discusses major developments that have occurred since 1991. Advances in the instrumentation and understanding of the key physical principles are the primary focus. Developments with electrospray and atmospheric pressure chemical ionization and variations encompassing adaptations for surface analysis, ambient air analysis, high throughput, and modification of the ionization mechanism are covered. An important and limiting consequence of atmospheric pressure chemical ionization, chemical noise, is discussed as is techniques being employed to ameliorate the problem. Ion transfer and transport from atmospheric pressure into deep vacuum is an area undergoing constant improvement and refinement so is given considerable consideration in this review.
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Affiliation(s)
- Thomas R Covey
- MDS Analytical Technologies, Sciex, Concord, Ontario, Canada L4K 4V8.
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Staub A, Schappler J, Rudaz S, Veuthey JL. CE-TOF/MS: Fundamental concepts, instrumental considerations and applications. Electrophoresis 2009; 30:1610-23. [DOI: 10.1002/elps.200800782] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Pantůčková P, Gebauer P, Boček P, Křivánková L. Electrolyte systems for on-line CE-MS: Detection requirements and separation possibilities. Electrophoresis 2009; 30:203-14. [DOI: 10.1002/elps.200800262] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Li HF, Liu J, Cai Z, Lin JM. Coupling a microchip with electrospray ionization quadrupole time-of-flight mass spectrometer for peptide separation and identification. Electrophoresis 2008; 29:1889-94. [DOI: 10.1002/elps.200700477] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Stutz H. Advances in the analysis of proteins and peptides by capillary electrophoresis with matrix-assisted laser desorption/ionization and electrospray-mass spectrometry detection. Electrophoresis 2005; 26:1254-90. [PMID: 15776483 DOI: 10.1002/elps.200410130] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
High throughput, outstanding certainty in peptide/protein identification, exceptional resolution, and quantitative information are essential pillars in proteome research. Capillary electrophoresis (CE) coupled to mass spectrometry (MS) has proven to meet these requirements. Soft ionization techniques, such as matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), have paved the way for the story of success of CE-MS in the analysis of biomolecules and both approaches are subject of discussion in this article. Meanwhile, CE-MS is far away from representing a homogeneous field. Therefore the review will cover a vast area including the coupling of different modes of CE (capillary zone electrophoresis, capillary isoelectric foscusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as on-line preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) applied to compensate for restricted detection sensitivity. Special attention is given to improvements in interfacing, namely addressing nanospray and coaxial sheath liquid design. Peptide mapping, collision-induced dissociation with subsequent tandem MS, and amendments in mass accuracy of instruments improve information validity gained from MS data. With 2-D on-line coupling of liquid chromatography (LC) and CE a further topic will be discussed. A special section is dedicated to recent attempts in establishing CE-ESI-MS in proteomics, in the clinical and diagnostic field, and in the food sector.
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Affiliation(s)
- Hanno Stutz
- University of Salzburg, Department of Molecular Biology, Division of Chemistry, Salzburg, Austria.
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Cook HA, Klampfl CW, Buchberger W. Analysis of melamine resins by capillary zone electrophoresis with electrospray ionization-mass spectrometric detection. Electrophoresis 2005; 26:1576-83. [PMID: 15759307 DOI: 10.1002/elps.200410058] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A method for the determination of the major components of (methoxymethyl)melamine resins, with quantitative analysis of unreacted melamine by capillary zone electrophoresis (CZE) using electrospray ionization-mass spectrometry (ESI-MS) is presented. Using a low background electrolyte (BGE) pH, components are separated according to their charge/ionic radius ratio with a distinctly different separation selectivity compared to the HPLC methods commonly employed in melamine-resin analysis. The use of a time-of-flight mass spectrometer (TOF-MS) was concluded to be necessary, as the complex samples studied required maximum sensitivity and resolution, which is clearly superior for TOF-MS detectors over their quadrupole counterparts. A standard curve of free melamine was determined with an R(2) = 0.999 over a concentration range of an order of magnitude. This method offers the unique separation selectivity of CZE as well as a quicker analysis time, especially for dimers compared to the HPLC methods used to date.
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Affiliation(s)
- Helmy A Cook
- Institute of Analytical Chemistry, Johannes Kepler University Linz, Linz, Austria.
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Liu CC, Zhang J, Dovichi NJ. A sheath-flow nanospray interface for capillary electrophoresis/mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2005; 19:187-192. [PMID: 15593250 DOI: 10.1002/rcm.1769] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have developed a novel sheath-flow interface for low-flow electrospray ionization mass spectrometry (ESI-MS) and capillary electrophoresis/electrospray mass spectrometry (CE/ESI-MS). The interface is composed of two capillaries. One is a tapered fused-silica ESI emitter suitable for microliter and nanoliter flow rate electrospray and the other is a tail-end gold-coated CE separation column that is inserted into the emitter. A sheath liquid is supplied between the column and the emitter capillaries. The gold coating and the sheath liquid are used as the conducting media for ESI and the CE circuit. This novel design was initially evaluated by an infusion ESI-MS analysis of the most common antiretroviral dideoxynucleosides, followed by CE/MS coupling analysis of several antidepressant drugs. With infusion studies, the effects of the sheath liquid and the sample flow rates on detection sensitivity and signal stability were investigated. For an emitter with an internal diameter of 30 microm, the optimum flow rates for the sheath and the sample were 200 and 300 nL/min, respectively. The main improvement of this approach in comparison with conventional sheath liquid approaches using an ionspray interface is the gain in sensitivity. Sensitivities were three times better for dideoxynucleosides analyzed by infusion and 12 times higher for antidepressant drugs analyzed by CE/MS with this interface compared with ionspray. The emitter is durable, disposable, and simple to fabricate.
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Kele Z, Ferenc G, Klement E, Tóth GK, Janáky T. Design and performance of a sheathless capillary electrophoresis/mass spectrometry interface by combining fused-silica capillaries with gold-coated nanoelectrospray tips. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2005; 19:881-885. [PMID: 15724233 DOI: 10.1002/rcm.1866] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A simple sheathless capillary electrophoresis (CE)/mass spectrometry (MS) interface was constructed by combining widely used nanospray needles with fused-silica capillaries and it was successfully applied for the separation of peptides. The end of the CE capillary was pulled to a taper, etched and then fitted into the metal-coated nanospray borosilicate capillary. The nanospray needle can be used for several CE runs, but it can be easily and rapidly changed in the case of accidental breakage or evaporation of the coating. A fast capillary electrochromatographic method was also developed for MS analysis of peptides containing numerous basic amino acids.
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Affiliation(s)
- Zoltán Kele
- Department of Medical Chemistry, University of Szeged, 6720 Szeged, Dóm tér 8, Hungary.
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Gross JH. Hyphenated Methods. Mass Spectrom (Tokyo) 2004. [DOI: 10.1007/3-540-36756-x_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Zhu K, Kim J, Yoo C, Miller FR, Lubman DM. High Sequence Coverage of Proteins Isolated from Liquid Separations of Breast Cancer Cells Using Capillary Electrophoresis-Time-of-Flight MS and MALDI-TOF MS Mapping. Anal Chem 2003; 75:6209-17. [PMID: 14616003 DOI: 10.1021/ac0346454] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A method has been developed for high sequence coverage analysis of proteins isolated from breast cancer cell lines. Intact proteins are isolated using multidimensional liquid-phase separations that permit the collection of individual protein fractions. Protein digests are then analyzed by both matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) peptide mass fingerprinting and by capillary electrophoresis-electrospray ionization (CE-ESI)-TOF MS peptide mapping. These methods can be readily interfaced to the relatively clean proteins resulting from liquid-phase fractionation of cell lysates with little sample preparation. Using combined sequence information provided by both mapping methods, 100% sequence coverage is often obtained for smaller proteins, while for larger proteins up to 75 kDa, over 90% coverage can be obtained. Furthermore, an accurate intact protein MW value (within 150 ppm) can be obtained from ESI-TOF MS. The intact MW together with high coverage sequence information provides accurate identification. More notably the high sequence coverage of CE-ESI-TOF MS together with the MS/MS information provided by the ion trap/reTOF MS elucidates posttranslational modifications, sequence changes, truncations, and isoforms that may otherwise go undetected when standard MALDI-MS peptide fingerprinting is used. This capability is critical in the analysis of human cancer cells where large numbers of expressed proteins are modified, and these modifications may play an important role in the cancer process.
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Affiliation(s)
- Kan Zhu
- Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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Chen YR, Tseng MC, Chang YZ, Her GR. A low-flow ce/electrospray ionization MS interface for capillary zone electrophoresis, large-volume sample stacking, and micellar electrokinetic chromatography. Anal Chem 2003; 75:503-8. [PMID: 12585476 DOI: 10.1021/ac026098c] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A simple and versatile low-flow interface has been developed for interfacing capillary electrophoresis (CE) with electrospray ionization (ESI) mass spectrometry. This low-flow interface showed better sensitivity than a conventional sheath liquid interface, primarily attributed to a low dilution factor and a reduction in the sprayer orifice size. The interface was also found to be more tolerant to the presence of nonvolatile salts. Because of tolerance to the surfactant SDS, this interface can be used to couple micellar electrokinetic chromatography (MEKC) with ESI-MS. The performance of the interface in an MEKC-MS application, as demonstrated in the analysis of triazines, was significantly better than that obtained with a conventional sheath liquid interface. Moreover, this interface can be easily used for large-volume sample-stacking (LVSS) applications. Using a series of phenols as a test case, an approximate 500-fold enrichment was achieved by LVSS in conjunction with the low-flow CE/MS interface described.
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Affiliation(s)
- Yet-Ran Chen
- Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC
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26
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Gelpí E. Interfaces for coupled liquid-phase separation/mass spectrometry techniques. An update on recent developments. JOURNAL OF MASS SPECTROMETRY : JMS 2002; 37:241-253. [PMID: 11921364 DOI: 10.1002/jms.297] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
An update is presented covering the latest developments in the interfacing of liquid-phase separation systems and mass spectrometers. The interfacing devices presented are those developed for continuous-flow matrix-assisted laser desorption/ionization, micro- and nano-liquid chromatography/masspectrometry (MS), capillary electrophoresis/MS and on-chip separation technologies/MS. From the information that can be found in the most recent literature on the topic, it is evident that the trend towards the miniaturization of separation and interface devices is gaining ground. This can be rationalized by the substantial gains in sensitivity for the detection and study of extremely low levels of analytes and especially of high molecular mass biopolymers.
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Affiliation(s)
- Emilio Gelpí
- Instituto de Investigaciones Biomédicas-CSIC-IDIBAPS, Roselló 161, 08036 Barcelona, Spain.
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27
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Gangl ET, Annan MM, Spooner N, Vouros P. Reduction of signal suppression effects in ESI-MS using a nanosplitting device. Anal Chem 2001; 73:5635-44. [PMID: 11774901 DOI: 10.1021/ac010501i] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrospray ionization mass spectrometry is a valuable tool in the identification and quantification of drug metabolites in biological fluids. However, there are many instances where matrix components present in these fluids interfere with analyte detection and prevent the acquisition of accurate or complete results. In some instances, the matrix can suppress ionization to such an extent that analytes are completely undetectable by MS. In this work, we investigate how ionization and ion-transfer efficiencies are affected by drastically reducing the flow into the MS. A postcolumn concentric flow-splitting device was constructed to allow the measurement of analyte signal and ionization suppression across a range of flow rates (0.1-200 microL/min). Using this device, the effects of flow rate on signal intensity and ionization suppression were measured in analytical experiments that included flow injection analysis MS, postcolumn addition LC-MS, and on-line LC-MS analysis of metabolites generated from rat liver microsomes. The device used to deliver 0.1 microL/min flows is referred to as a nanosplitter because it achieved high split ratios (2000:1), producing flow rates comparable to those observed in nanoelectrospray. The nanosplitter maintained chromatographic integrity with high fidelity and allowed the direct comparison of analyte signal across a range of flow rates (0.1-200 microL/min). A significant improvement in concentration and mass sensitivity as well as a reduction in signal suppression is observed when the performance at 200 versus 0.1 microL/min flow rate is compared. Using this specially designed concentric splitting device, the advantages of ultralow flow ESI were easily exploited for applications employing large bore chromatography.
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Affiliation(s)
- E T Gangl
- Barnett Institute and Department of Chemistry, Northeastern University, Boston, Massachusetts 02115, USA
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28
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Rohner TC, Rossier JS, Girault HH. Polymer microspray with an integrated thick-film microelectrode. Anal Chem 2001; 73:5353-7. [PMID: 11816559 DOI: 10.1021/ac015557r] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A microfabrication process leading to a sheathless electrospray interface for mass spectrometry analysis is described. Photoablation is performed on a polymer substrate, allowing the integration of a thick-film conductive track in a sealed microchannel. High voltage is supplied close to the outlet, through an embedded microelectrode. The microspray is generated directly from the edge of the substrate without any tip addition. The flexibility of this technology provides a wide range of dimensions for the probe and the microelectrode design, including location, shape, and conductive material used. Thanks to the thick-film microelectrode and the hydrophobicity of the polymer, which avoids solution spreading at the outlet, the device has been found to be an efficient ionization source providing a stable MS signal through time. Moreover, the same device can be used several times without failure. The performance of the microspray has been studied in simple infusion mode for proteins and reserpine MS analyses. The detection limit of reserpine was found to be at the picomolar level in full-scan MS mode. It implies also that approximately 500 zmol was read consumed during 3 min of infusion. A dynamic range from pico- to millimolar level is also underlined.
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Affiliation(s)
- T C Rohner
- Laboratoire d'Electrochimie, Ecole Polytechnique Fédérale de Lausanne, Switzerland
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29
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Hille JM, Freed AL, Wätzig H. Possibilities to improve automation, speed and precision of proteome analysis: a comparison of two-dimensional electrophoresis and alternatives. Electrophoresis 2001; 22:4035-52. [PMID: 11824628 DOI: 10.1002/1522-2683(200111)22:19<4035::aid-elps4035>3.0.co;2-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Proteome analysis requires fast methods with high separation efficiencies in order to screen the various cell and tissue types for their proteome expression and monitor the effect of environmental conditions and time on this expression. The established two-dimensional gel electrophoresis (2-DE) is by far too slow for a consequential screening. Moreover, it is not precise enough to observe changes in protein concentrations. There are various approaches that promise faster, automated proteome analysis. This article concentrates on capillary (CT isoelectric focusing coupled to mass spectrometry (CIEF-MSn) and preparative IEF followed by size-exclusion chromatography, hyphenated with MS (PIEF-SEC-MS). These two approaches provide a similar separation pattern as the established 2-DE technique and therefore allow for the continued use of data based on this traditional approach. Their performances have been discussed and compared to 2-DE, evaluating 169 recent articles. Data on analysis time, automation, the detection limit, quantitation, peak capacity, mass and pI accuracy, as well as on the required sample amount are compared in a table.
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Affiliation(s)
- J M Hille
- Institute of Pharmaceutical Chemistry, University of Braunschweig, Germany
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30
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Patrick JS, Lagu AL. Review applications of capillary electrophoresis to the analysis of biotechnology-derived therapeutic proteins. Electrophoresis 2001; 22:4179-96. [PMID: 11824636 DOI: 10.1002/1522-2683(200111)22:19<4179::aid-elps4179>3.0.co;2-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The number of proteins produced by recombinant DNA technology continues to grow at a rapid pace. In this review, the emphasis is on proteins that are of therapeutic interest. Aspects of protein analysis, such as glycoform separation of proteins produced in mammalian cells and the separation of oligosaccharides for structure elucidation, are covered. The use of antibodies as therapeutic proteins is growing and currently antibodies are the largest class of proteins produced by biotechnology. This has merited a separate section on analysis of antibodies by capillary electrophoresis (CE). Applications of mass spectrometry as an ancillary technique, used in conjunction with CE, are also covered briefly. This review covers the literature since 1999.
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Affiliation(s)
- J S Patrick
- Lilly Research Laboratories, A Division of Eli Lilly and Co., Indianapolis, IN 46285, USA
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31
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Abstract
A novel microfabricated nozzle has been developed for the electrospray of liquids from microfluidic devices for analysis by mass spectrometry. The electrospray device was fabricated from a monolithic silicon substrate using deep reactive ion etching and other standard semiconductor techniques to etch nozzles from the planar surface of a silicon wafer. A channel extends through the wafer from the tip of the nozzle to a reservoir etched into the opposite planar surface of the wafer. Nozzle diameters as small as 15 microm have been fabricated using this method. The microfabricated electrospray device provides a reproducible, controllable, and robust means of producing nano-electrospray of a liquid sample. The electrospray device was interfaced to an atmospheric pressure ionization time-of-flight mass spectrometer using continuous infusion of test compounds at low nanoliter-per-minute flow rates. Nozzle-to-nozzle signal intensity reproducibility using 10 nozzles was demonstrated to be 12% with single-nozzle signal stability routinely less than 4% relative standard deviation (RSD). Solvent compositions have been electrosprayed ranging from 100% organic to 100% aqueous. The signal-to-noise ratio from the infusion of a 10 nM cytochrome c solution in 100% water at 100 nL/min was 450:1. Microchip electrospray nozzles were compared with pulled capillaries for overall sensitivity and signal stability for small and large molecules. The microchip electrospray nozzles showed a 1.5-3-times increase in sensitivity compared with that from a pulled capillary, and signal stability with the microchip was 2-4% RSD compared with 4-10% with a pulled capillary. Electrospray device lifetimes achieved thus far have exceeded 8 h of continuous operation and should be sufficient for typical microfluidic applications. The total volume of the electrospray device is less than 25 pL, making it suitable for combination with microfluidic separation devices.
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32
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Li J, Kelly JF, Chernushevich I, Harrison DJ, Thibault P. Separation and identification of peptides from gel-isolated membrane proteins using a microfabricated device for combined capillary electrophoresis/nanoelectrospray mass spectrometry. Anal Chem 2000; 72:599-609. [PMID: 10695148 DOI: 10.1021/ac990986z] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The coupling of microfabricated devices to nanoelectrospray mass spectrometers using both a triple quadrupole and a quadrupole time-of-flight mass spectrometer (QqTOF MS) is presented for the analysis of trace-level membrane proteins. Short disposable nanoelectrospray emitters were directly coupled to the chip device via a low dead volume connection. The analytical performance of this integrated device in terms of sensitivity and reproducibility was evaluated for standard peptide mixtures. A concentration detection limit ranging from 3.2 to 43.5 nM for different peptides was achieved in selected ion monitoring, thus representing a 10-fold improvement in sensitivity compared to that of microelectrospray using the same chip/mass spectrometer. Replicate injections indicated that reproducibility of migration time was typically less than 3.1% RSD whereas RSD values of 6-13% were observed on peak areas. Although complete resolution of individual components is not typically achieved for complex digests, the present chip capillary electrophoresis (chip-CE) device enabled proper sample cleanup and partial separation of multicomponent samples prior to mass spectral identification. Analyses of protein digests were typically achieved in less than 1.5 min with peak widths of 1.8-2.5 s (half-height definition) as indicated from individual reconstructed ion electropherograms. The application of this chip-CE/QqTOF MS system is further demonstrated for the identification of membrane proteins which form a subset of the Haemophilus influenzae proteome. Bands first separated by 1D-gel electrophoresis were excised and digested, and extracted tryptic peptides were loaded on the chip without any further sample cleanup or on-line adsorption preconcentration. Accurate molecular mass determination (< 5 ppm) in peptide-mapping experiments was obtained by introducing an internal standard via a postseparation channel. The analytical potential of this integrated device for the identification of trace-level proteins from different strains of H. influenzae is demonstrated using both peptide mass-fingerprint database searching and on-line tandem mass spectrometry.
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Affiliation(s)
- J Li
- Institute for Biological Sciences, Ottawa, Ontario, Canada
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33
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Feng B, Smith RD. A simple nanoelectrospray arrangement with controllable flowrate for mass analysis of submicroliter protein samples. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2000; 11:94-99. [PMID: 10631670 DOI: 10.1016/s1044-0305(99)00124-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A simple arrangement for nanoelectrospray ionization using a conventional syringe pump connected to a pulled unmodified capillary has been evaluated. This arrangement avoids several disadvantages associated with metal-coated nanoelectrospray emitters. The relatively large orifice (approximately 9 microns) at the pulled capillary tip reduces sample clogging and the use of the pump minimizes spray disruption due to gas bubbles. Subattomole detection limit was achieved with nanomolar protein sample solutions at 5-10 nL/min flowrates using an LCQ mass spectrometer. Submicroliter samples can be loaded from the tip orifice and stored inside the capillary to virtually eliminate any dead volume, and then be electrosprayed for extended periods at well-controlled flowrates.
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Affiliation(s)
- B Feng
- Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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34
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Vrouwe EX, Gysler J, Tjaden UR, van der Greef J. Chip-based capillary electrophoresis with an electrodeless nanospray interface. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2000; 14:1682-1688. [PMID: 10962491 DOI: 10.1002/1097-0231(20000930)14:18<1682::aid-rcm78>3.0.co;2-e] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A sheathless and electrodeless nanospray interface has been used to interface a polycarbonate capillary electrophoresis (CE) chip to a mass spectrometer (MS). The chip was made of two flat polycarbonate plates which were bolted together. Channels were imprinted in one of the plates with metal wires, using a hydraulic press. A short tapered capillary connected to the chip was used as the nanospray emitter. The advantage of this electrodeless interface is that it was not necessary to apply a electrospray voltage to the chip or the nanospray emitter. Instead, the CE voltage already applied to the buffer compartment on the chip, to drive the electrophoresis, was used to generate the spray also. A low conductivity buffer of 1.25 mmol/L ammonium acetate in 80% methanol was used to obtain a large electric field across the buffer channel. The performance of the device was evaluated by analyzing a mixture of three beta-agonists Relative standard deviation (RSD) values obtained were between 4.8 and 5.0%. A sample concentration of 40 nmol/L resulted in a signal-to-noise ratio of 2 to 5 for the different components. Compared to a conventional CE analysis in a fused silica capillary with UV detection, only a minor loss of resolution was observed, which can be attributed to the design of the chip.
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Affiliation(s)
- E X Vrouwe
- Department of Analytical Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
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35
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Jin X, Kim J, Parus S, Lubman DM, Zand R. On-line capillary electrophoresis/microelectrospray ionization-tandem mass spectrometry using an ion trap storage/time-of-flight mass spectrometer with SWIFT technology. Anal Chem 1999; 71:3591-7. [PMID: 10464485 DOI: 10.1021/ac990221r] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The development of a system capable of the speed required for on-line capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) of tryptic digests is described. The ion trap storage/reflectron time-of-flight (IT/reTOF) mass spectrometer is used as a nonscanning detector for rapid CE separation, where the peptides are ionized on-line using electrospray ionization (ESI). The ESI produced ions are stored in the ion trap and dc pulse injected into the reTOF-MS at a rate sufficient to maintain the separation achieved by CE. Using methodology generated by software and hardware developed in our lab, we can produce SWIFT (Stored Waveform Inverse Fourier Transform) ion isolation and TICKLE activation/fragmentation voltage waveforms to generate MS/MS at a rate as high as 10 Hz so that the MS/MS spectra can be optimized on even a 1-2 s eluting peak. In CE separations performed on tryptic digests of dogfish myelin basic protein (MBP) where eluting peaks 4-8 s wide are observed, it is demonstrated that an acquisition rate of 4 Hz provides > 20 spectra/peak and is more than sufficient to provide optimized MS/MS spectra of each of the eluting peaks in the electropherogram. The detailed structural analysis of dogfish MBP including several posttranslational modifications using CE-MS and CE-MS/MS is demonstrated using this method with < 10 fmol of material consumed.
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Affiliation(s)
- X Jin
- Department of Chemistry, University of Michigan, Ann Arbor 48109-1055, USA
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36
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Jin X, Chen Y, Lubman DM, Misek D, Hanash SM. Capillary electrophoresis/tandem mass spectrometry for analysis of proteins from two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 1999; 13:2327-2334. [PMID: 10567930 DOI: 10.1002/(sici)1097-0231(19991215)13:23<2327::aid-rcm792>3.0.co;2-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Capillary electrophoresis/time-of-flight mass spectrometry(CE/TOFMS) has been used for analysis of in-gel digests of protein spots excised from two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (2-D SDS-PAGE). An off-line purification and preconcentration procedure with a Zip Tip is used before CE/TOFMS analysis which allows for detection of protein spots with <1 picomole of material from 2-D gels. The off-line procedure provides sufficient purification for analysis while maintaining the quality of the CE separation. Using this procedure, several proteins from Coomassie Blue and zinc negatively stained gels are identified by the peptide maps generated and database searching. CE/TOF tandem mass spectrometry is used for the confirmation of database searching results and structural analysis of peptides that do not match the expected peptide maps obtained from the database in order to identify structural modifications. Several modifications were pinpointed and identified by this method.
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Affiliation(s)
- X Jin
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
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