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Han Z, Hishida S, Chen LC. Formation of Alternating Surfactant-Enriched and Surfactant-Depleted Phases in the Taylor Cone of a Nanoelectrospray. Anal Chem 2024; 96:7297-7303. [PMID: 38682329 DOI: 10.1021/acs.analchem.4c01379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2024]
Abstract
The electrospray ionization of highly conductive solutions containing Triton X-100, a nonionic surfactant, is found to induce alternating periods of surfactant enrichment and depletion when the concentration of the surfactant is near the critical micelle concentration (CMC) and when the flow rate is on the order of 10 nL/min. Analyzing the surfactant-protein mixture shows that the protein is partially denatured during the surfactant enrichment. The measurement of the phospholipid and oligosaccharide mixture prepared in the surfactant solution shows that the ion signal of the lipid is in phase with, and the hydrophilic oligosaccharide is out of phase with the surfactant signal. The results suggest that this novel phenomenon can be exploited for in situ separation of compounds in ESI-MS. Besides the ion signal, the condition of the alternating phase is also reflected in the spray current and Taylor cone's apex angle. The phase separation is likely related to the formation of a micelle in the Taylor cone and can be selectively triggered by tuning the flow rate with emitter voltage for an on-demand application.
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Affiliation(s)
- Zhongbao Han
- College of Chemistry and Chemical Engineering, Shenyang Normal University, Shenyang 110034, China
| | - Shoki Hishida
- Faculty of Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan
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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: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 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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Han Z, Omata N, Chen LC. Probing Acid-Induced Compaction of Denatured Proteins by High-Pressure Electrospray Mass Spectrometry. Anal Chem 2023; 95:14816-14821. [PMID: 37733605 DOI: 10.1021/acs.analchem.3c03183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/23/2023]
Abstract
Further increase in the acidity in the most denaturing acidic solution is known to induce compaction of the fully unfolded protein into a compact molten globule. The phenomenon of "acid-induced folding of proteins" takes place at pH ∼1 in strong acid aqueous solutions with high electrical conductivity and surface tension, a condition that is difficult to handle using conventional electrospray ionization methods for mass spectrometry. Here, high-pressure electrospray ionization (HP-ESI) is used to produce well-resolved mass spectra for proteins in strong acids with pH as low as 1. The compaction of protein conformation is indicated by a large shift in the charge state from high charges to native-like low charges. The addition of salt to the protein in the most denaturing condition also reproduces the compaction effect, thereby supporting the role of anions in this phenomenon. Similar compaction of proteins is also observed in organic solvent/acid mixtures. The charge state of the compacted protein depends on the type of anions that formed ion pairs with a positive charge on the protein. The dissociation of ion pairs during the ionization process forms neutral acids that can be observed by HP-ESI using a soft ion introduction configuration.
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Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi400-8511, Japan
| | - Nozomu Omata
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi400-8511, Japan
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Wang T, Li H, Allen N, Ferraro I, Li A. Ultra-low current electrospray ionization of chloroform solution for the analysis of perfluorinated sulfonic acids. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37 Suppl 1:e9501. [PMID: 36879515 DOI: 10.1002/rcm.9501] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/13/2023] [Accepted: 03/03/2023] [Indexed: 06/18/2023]
Abstract
RATIONALE Femtoamp and picoamp electrospray ionization (ESI) characteristics of a nonpolar solvent were explored. The direct ESI mass spectrometry analysis of chloroform extract solution enabled rapid analysis of perfluorinated sulfonic acid analytes in drinking water. METHODS Neat chloroform solvent and extracts were directly used in a typical wire-in ESI setup using micrometer emitter tips. Ionization currents were measured with femtoamp sensitivity while ramping the spray voltage from 0 to -5000 V. Methanol was used as a comparison to illustrate the characteristics of electrospraying chloroform. The effects of spray voltage and inlet temperature were studied. A liquid-liquid extraction workflow was developed to analyze perfluorooctanoate sulfonate (PFOS) in drinking water using an ion-trap mass spectrometer. RESULTS The ionization onset of chloroform solution was 41 ± 17 fA at 300 V. The ionization current gradually increased with voltage while remaining below 100 pA when using voltages up to -5000 V. The ion signal of PFOS was significantly enhanced to improve the limit of detection (LoD) to 25 ppt in chloroform. Coupled with a liquid-liquid extraction workflow, LoD of 0.38-5.1 ppt and a quantitation range of 5-400 ppt were achieved for perfluorinated sulfonic compounds in 1-ml water samples. CONCLUSIONS Femtoamp and picoamp modes expand the solvent compatibility range of ESI and can enable quantitative analysis in parts per trillion (ppt) concentrations.
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Affiliation(s)
| | - Huishan Li
- University of New Hampshire, Durham, NH, USA
| | | | - Ian Ferraro
- University of New Hampshire, Durham, NH, USA
| | - Anyin Li
- University of New Hampshire, Durham, NH, USA
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Han Z, Hishida S, Omata N, Matsuda T, Komori R, Chen LC. Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS. Anal Chem 2023. [PMID: 37418336 DOI: 10.1021/acs.analchem.3c01768] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
An electrospray operated in the steady cone-jet mode is highly stable but the operating state can shift to pulsation or multijet modes owing to changes in flow rate, surface tension, and electrostatic variables. Here, a simple feedback control system was developed using the spray current and the apex angle of a Taylor cone to determine the error signal for correcting the emitter voltage. The system was applied to lock the cone-jet mode operation against external perturbations. For a pump-driven electrospray at a regulated flow rate, the apex angle of the Taylor cone decreased with increasing voltage. In contrast, for a voltage-driven electrospray with low flow resistance, the angle was found to increase with the emitter voltage. A simple algorithm based on iterative learning control was formulated and implemented using a personal computer to automatically correct the emitter voltage in response to the error signal. For voltage-driven electrospray ionization (ESI), the feedback control of the spray current can also be used to regulate the flow rate to an arbitrary value or pattern. Electrospray ionization-mass spectrometry (ESI-MS) with feedback control was demonstrated to produce ion signal acquisition with long-term stability that was insusceptible to the emulated external disturbances.
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Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Shoki Hishida
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Nozomu Omata
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Takeshi Matsuda
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Ryoki Komori
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
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Han Z, Omata N, Matsuda T, Hishida S, Takiguchi S, Komori R, Suzuki R, Chen LC. Tuning oxidative modification by a strong electric field using nanoESI of highly conductive solutions near the minimum flow rate. Chem Sci 2023; 14:4506-4515. [PMID: 37152264 PMCID: PMC10155921 DOI: 10.1039/d2sc07113d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 03/27/2023] [Indexed: 05/09/2023] Open
Abstract
Oxidative modification is usually used in mass spectrometry (MS) for labeling and structural analysis. Here we report a highly tunable oxidation that can be performed in line with the nanoESI-MS analysis at the same ESI emitter without the use of oxidative reagents such as ozone and H2O2, and UV activation. The method is based on the high-pressure nanoESI of a highly conductive (conductivity >3.8 S m-1) aqueous solution near the minimum flow rate. The ion source is operated under super-atmospheric pressure (0.5 MPa gauge pressure) to avoid the contribution of electric discharge. The analyte at the tip of the Taylor cone or in the emitter droplet can be locally oxidized in an on-demand manner by varying the nanoflow rate. With an offline nanoESI, the degree of oxidation, i.e., the average number of incorporated oxygen atoms, can be finely tuned by voltage modulation using spray current as the feedback signal. Oxidations of easily oxidized residues present in peptides/proteins and the double bonds of the unsaturated phosphatidylcholine occur at low flow rate operation (<5 nL min-1) when the electric field at the tip of the Taylor cone and the initially produced charged droplet reaches approximately 1.3 V nm-1. The oxidized ion signal responds instantaneously to changes in flow rate, indicating that the oxidation is highly localized. Using isotope labeling, it was found that the incorporated oxygen primarily originates from the gas phase, suggesting a direct oxidation pathway for the analyte enriched on the liquid surface via the reactive oxygen atoms formed by the strong electric field.
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Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Nozomu Omata
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Takeshi Matsuda
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Shoki Hishida
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Shuuhei Takiguchi
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Ryoki Komori
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Riku Suzuki
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi 4-3-11, Takeda Kofu Yamanashi 400-8511 Japan +81-55-220-8072
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Han Z, Komori R, Suzuki R, Omata N, Matsuda T, Hishida S, Shuuhei T, Chen LC. Bipolar Electrospray from Electrodeless Emitters for ESI without Electrochemical Reactions in the Sprayer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:728-736. [PMID: 36815710 DOI: 10.1021/jasms.2c00382] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
A bipolar ESI source is developed to generate a simultaneous emission of charged liquid jets of opposite polarity from an electrodeless sprayer. The sprayer consists of two emitters, and the electrosprays are initiated by applying a high potential difference (HV) across the counter electrodes facing each emitter. The sprayer and the liquid delivery system are made of all insulators without metal components, thus enabling the total elimination of electrochemical reactions taking place at the liquid-electrode interface in the typical electrosprayer. The bipolar electrospray has been implemented using an online configuration that uses a syringe pump for flow rate regulation and an offline configuration that relies on HV for adjusting the flow rate. The voltage-current and flow rate-current relationships of bipolar electrospray were found to be similar to the standard electrospray. The application of bipolar ESI to the mass spectrometry of protein, peptide, and metallocene without electrochemically induced oxidation/reduction is demonstrated.
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Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Ryoki Komori
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Riku Suzuki
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Nozomu Omata
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Takeshi Matsuda
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Shoki Hishida
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Takiguchi Shuuhei
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
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Han Z, Chen LC. A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS. Anal Chem 2022; 94:16015-16022. [DOI: 10.1021/acs.analchem.2c02997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Zhongbao Han
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
| | - Lee Chuin Chen
- Faculty of Engineering, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi 400-8511, Japan
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