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Lei W, Hu J, Chen HY, Xu JJ. Combined strategies for suppressing nonspecific cationic adduction to G-quadruplexes in electrospray ionization mass spectrometry. Anal Chim Acta 2022; 1220:340146. [DOI: 10.1016/j.aca.2022.340146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/21/2022] [Accepted: 07/03/2022] [Indexed: 11/01/2022]
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2
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Wu J, Zhang W, Ouyang Z. On-Demand Mass Spectrometry Analysis by Miniature Mass Spectrometer. Anal Chem 2021; 93:6003-6007. [PMID: 33819018 DOI: 10.1021/acs.analchem.1c00575] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Electrospray ionization (ESI) has become a powerful tool for the analysis of biomolecules by mass spectrometry (MS). The process of ESI is difficult to control, and side reactions such as electrochemical reactions can occur during the ESI process because of the high voltages applied. Herein, a novel on-demand MS analysis method was developed based on discontinuous ion injection-induced ESI on a miniature MS system. Highly efficient ionization was enabled under low voltages (<300 V) using a discontinuous atmospheric pressure interface. On-demand ionization showed comparable sensitivity with regular nanoESI for the analyses of a series of compounds. It was found to be softer than regular ESI or nanoESI methods for ionization of proteins such as myoglobin and cytochrome C. As the ionization finished as soon as the interface was closed, the sample consumption was observed to reduce significantly for MS analysis, allowing single-cell analysis with multiple MS and MS/MS measurements.
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Affiliation(s)
- Junhan Wu
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084 China
| | - Wenpeng Zhang
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084 China
| | - Zheng Ouyang
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084 China
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3
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Hu J, Lei W, Wang J, Chen HY, Xu JJ. Preservation of Protein Zwitterionic States in the Transition from Solution to Gas Phase Revealed by Sodium Adduction Mass Spectrometry. Anal Chem 2019; 91:7858-7863. [PMID: 31134800 DOI: 10.1021/acs.analchem.9b01602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structural characterization of proteins and their interaction network mapping in the gas phase highlights the need to preserve their most nativelike conformers in the transition from the solution to gas phase. Zwitterionic interactions in a protein are weak bonds between oppositely charged residues, which make an important contribution to protein stability. However, it is still not clear whether the native zwitterionic states of proteins can be retained or not when it is transferred from the solution to gas phase. Using the nonspecific Na+ adduction as a novel signature, here we show that the zwitterionic states of proteins can be preserved when a moderated droplet desolvation condition (temperature <30 °C) is used in native electrospray ionization mass spectrometry. The very low-level nonspecific metal adduction to proteins under such conditions also enables rapid and direct determination of the binding states of metal-binding proteins and sensitive detection of proteins from solutions containing highly concentrated involatile salts (e.g., 50 mM NaCl). We believe that our findings can be instructive for performing mass spectrometric analysis of proteins and useful for protein ions desalting which simply involves altering the temperature and flow rate of drying gas in the desolvation region.
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Affiliation(s)
- Jun Hu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Wen Lei
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Jiang Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Hong-Yuan Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Jing-Juan Xu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
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4
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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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5
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Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization. Anal Chim Acta 2017; 957:20-28. [PMID: 28107830 DOI: 10.1016/j.aca.2016.12.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/20/2016] [Accepted: 12/25/2016] [Indexed: 11/21/2022]
Abstract
Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10-2 s to 10-1 s and Reynolds numbers on the order of 103 to 104. The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m2 area, 570 m3 volume) was demonstrated for a 60-min period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 min of exposure.
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6
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Fukuda T, Hike H, Usui F, Bando Y, Nishimura T, Kodama T, Kawamura T. An improvement on mass spectrometry-based epigenetic analysis of large histone-derived peptides by using the Ionization Variable Unit interface. Anal Biochem 2015; 486:14-6. [DOI: 10.1016/j.ab.2015.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 05/31/2015] [Accepted: 06/01/2015] [Indexed: 11/28/2022]
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7
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Yao Y, Shams-Ud-Doha K, Daneshfar R, Kitova EN, Klassen JS. Quantifying protein-carbohydrate interactions using liquid sample desorption electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:98-106. [PMID: 25315460 DOI: 10.1007/s13361-014-1008-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/03/2014] [Accepted: 09/05/2014] [Indexed: 06/04/2023]
Abstract
The application of liquid sample desorption electrospray ionization mass spectrometry (liquid sample DESI-MS) for quantifying protein-carbohydrate interactions in vitro is described. Association constants for the interactions between lysozyme and β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc and β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc, and between a single chain antibody and α-D-Galp-(1 → 2)-[α-D-Abep-(1 → 3)]-α-D-Manp-OCH3 and β-D-Glcp-(1 → 2)-[α-D-Abep-(1 → 3)]-α-D-Manp-OCH3 measured using liquid sample DESI-MS were found to be in good agreement with values measured by isothermal titration calorimetry and the direct ESI-MS assay. The reference protein method, which was originally developed to correct ESI mass spectra for the occurrence of nonspecific ligand-protein binding, was shown to reliably correct liquid sample DESI mass spectra for nonspecific binding. The suitability of liquid sample DESI-MS for quantitative binding measurements carried out using solutions containing high concentrations of the nonvolatile biological buffer phosphate buffered saline (PBS) was also explored. Binding of lysozyme to β-D-GlcNAc-(1 → 4)-β-D-GlcNAc-(1 → 4)-D-GlcNAc in aqueous solutions containing up to 1× PBS was successfully monitored using liquid sample DESI-MS; with ESI-MS the binding measurements were limited to concentrations less than 0.02 X PBS.
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Affiliation(s)
- Yuyu Yao
- Alberta Glycomics Center and Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada
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8
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Rahman MM, Mandal MK, Hiraoka K, Chen LC. High pressure nanoelectrospray ionization mass spectrometry for analysis of aqueous solutions. Analyst 2014; 138:6316-22. [PMID: 23979728 DOI: 10.1039/c3an00699a] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nanoelectrospray ionization (nanoESI) with a very fine emitter and nanoliter solution flow rate is known to be suitable for aqueous solutions. However, under atmospheric pressure, its stability with aqueous solutions is not always guaranteed particularly in the negative ion mode where corona and arc discharge tend to occur more easily. Electrical discharge can be quenched to a certain extent by adding electron scavenging gases like SF6 or CO2 to the ion source. The onset potential that is required to induce the discharge also increases with an increase of gas pressure. Recently, we have reported on a series of high pressure electrospray ion sources that were stable in both positive and negative ion modes using air or N2 as the working gas. In this paper, we compare the performance of nanoelectrospray under atmospheric pressure and super-atmospheric pressure for the analysis of samples in aqueous solution. The comparative study was performed using the same ion source chamber that could be pressurized up to 6 bar. The pressure in the first pumping stage of the mass spectrometer was kept constant when the ion source pressure was changed by using an additional pump with variable pumping speed. High pressure nanoESI optimized at 2-3 bar demonstrated a 3-5 times improvement in ion signal intensity compared to atmospheric pressure nanoESI, and the signal stability was significantly improved particularly in the negative mode.
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Affiliation(s)
- Md Matiur Rahman
- Clean Energy Research Center, University of Yamanashi, 4-3-11, Takeda, Kofu, Yamanashi, 400-8511 Japan
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9
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Jurcicek P, Liu L, Zou H, An Z, Xiao H. Design, simulation and evaluation of improved air amplifier incorporating an ion funnel for nano-ESI MS. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2014; 20:143-154. [PMID: 24895774 DOI: 10.1255/ejms.1269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
An improved air amplifier design that takes advantage of the combined effects of aerodynamic and electrodynamic focusing was developed to couple a nanoelectrospray ionisation (nano-ESI) source and the heated mass spectrometer inlet to improve the sensitivity of a mass spectrometer. The new design comprises an electrodynamic ion funnel integrated into the main air pathway of the air amplifier to more effectively focus and transmit gas-phase ions from the nano-ESI source into the heated mass spectrometer inlet. Numerical computational fluid dynamics simulations were carried out using a commercial software package, ANSYS FLUENT, to provide more detailed information about the device's performance. The gas flow field as well as the electric field patterns and the Lagrangian ion motion were conveniently simulated using this single package and custom-written, user-defined functions. Experimental results show a nearly five-fold improvement in reserpine ion intensity with the air amplifier operated at a nitrogen gauge pressure of 40 kPa and no direct current (DC) or radiofrequency (RF) potentials applied to the ion funnel when the distance between the electrospray emitter and sampling inlet tube was 24 mm, as compared to direct sample infusion from the same distance without the air amplifier. More importantly, a nearly three-fold additional gain in ion intensity was measured when both DC and RF potentials were co-applied, resulting in more than a 13-fold overall ion intensity gain which could be attributed to the combined air amplifier aerodynamic and ion funnel electrodynamic focusing effect.
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10
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Chen CH, Lin Z, Garimella S, Zheng L, Shi R, Cooks RG, Ouyang Z. Development of a mass spectrometry sampling probe for chemical analysis in surgical and endoscopic procedures. Anal Chem 2013; 85:11843-50. [PMID: 24251679 DOI: 10.1021/ac4025279] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A sampling probe based on ambient desorption ionization was designed for in vivo chemical analysis by mass spectrometry in surgical and endoscopic procedures. Sampling ionization of analytes directly from tissue was achieved by sealing the sampling tip against the tissue surface without allowing leakage of the auxiliary gas used for desorption ionization. The desorbed charged species were transferred over a long distance (up to 4 m) through a flexible tube of internal diameter as small as 1/16 in. to the inlet of the mass spectrometer used for analysis. The conditions used for desorption electrospray ionization (DESI) were optimized to achieve biocompatibility for clinical applications while obtaining adequate efficiency for the analysis. This optimization involved the removal of high voltage and use of pure water as a spray solvent instead of the organic solvents or aqueous mixtures normally used. Improved sensitivity was achieved under these conditions by increasing the gas flow rate in the transfer tube. The destructive effect on tissue surfaces associated with typical desorption ionization was avoided by altering the local gas dynamics in the sample area without compromising the overall analysis efficiency.
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Affiliation(s)
- Chien-Hsun Chen
- Weldon School of Biomedical Engineering, Purdue University , West Lafayette, Indiana 47907
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11
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Vortex focusing of ions produced in corona discharge. Talanta 2013; 110:39-45. [DOI: 10.1016/j.talanta.2013.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 01/25/2013] [Accepted: 02/05/2013] [Indexed: 11/19/2022]
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12
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Chen TC, Xu W, Garimella S, Ouyang Z. Study of the efficiency for ion transfer through bent capillaries. JOURNAL OF MASS SPECTROMETRY : JMS 2012; 47:1466-1472. [PMID: 23147823 DOI: 10.1002/jms.3117] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Discontinuous atmospheric pressure interfaces (DAPIs) with bent capillaries represent a highly simplified and flexible means for introducing ions into a vacuum manifold for mass analysis or gas phase ion reactions. In this work, a series of capillaries of different radians and curvatures were used with DAPI for studying the impact of the capillary bending on the ion transfer. The variation of transfer efficiency was systematically characterized for dry and solvated ions. The efficiency loss for dry ions was less than one order of magnitude, even with a three-turn bent capillary. The transfer of solvated ions generated by electrospray was found to be minimally impacted by the bending of the transfer capillary. For multiply protonated ions, the transfer efficiency for ions at lower charge states could be relatively well retained, presumably due to the lower reactivity associated with proton transfer reaction and the compensation in intensity by conversion of ions at higher charge states.
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Affiliation(s)
- Tsung-Chi Chen
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
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13
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El-Hawiet A, Kitova EN, Klassen JS. Quantifying Carbohydrate–Protein Interactions by Electrospray Ionization Mass Spectrometry Analysis. Biochemistry 2012; 51:4244-53. [DOI: 10.1021/bi300436x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Amr El-Hawiet
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
| | - Elena N. Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
| | - John S. Klassen
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G
2G2
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14
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Sterling HJ, Cassou CA, Susa AC, Williams ER. Electrothermal supercharging of proteins in native electrospray ionization. Anal Chem 2012; 84:3795-801. [PMID: 22409200 DOI: 10.1021/ac300468a] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The formation of high charge-state protein ions with nanoelectrospray ionization (nESI) from purely aqueous ammonium bicarbonate solutions at neutral pH, where the proteins have native or native-like conformations prior to ESI droplet formation, is demonstrated. This "electrothermal" supercharging method depends on the temperature of the instrument entrance capillary, the nESI spray potential, and the solution ionic strength and buffer, although other factors almost certainly contribute. Mass spectra obtained with electrothermal supercharging appear similar to those obtained from denaturing solutions where charging beyond the total number of basic sites can be achieved. For example, a 17+ ion of bovine ubiquitin was formed by nESI of a 100 mM ammonium bicarbonate, pH 7.0, solution, which is three more charges than the total number of basic amino acids plus the N-terminus. Heating of the ESI droplets in the vacuum/atmosphere interface and the concomitant denaturation of the protein in the ESI droplets prior to ion formation appears to be the primary origin of the very high charge-state ions formed from these purely aqueous, buffered solutions. nESI mass spectra resembling those obtained under traditional native or denaturing conditions can be reversibly obtained simply by toggling the spray voltage between low and high values.
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Affiliation(s)
- Harry J Sterling
- Department of Chemistry, University of California, Berkeley, California 94720-1460, United States
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15
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Kitova EN, El-Hawiet A, Schnier PD, Klassen JS. Reliable determinations of protein-ligand interactions by direct ESI-MS measurements. Are we there yet? JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:431-41. [PMID: 22270873 DOI: 10.1007/s13361-011-0311-9] [Citation(s) in RCA: 188] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 11/25/2011] [Accepted: 11/29/2011] [Indexed: 05/11/2023]
Abstract
The association-dissociation of noncovalent interactions between protein and ligands, such as other proteins, carbohydrates, lipids, DNA, or small molecules, are critical events in many biological processes. The discovery and characterization of these interactions is essential to a complete understanding of biochemical reactions and pathways and to the design of novel therapeutic agents that may be used to treat a variety of diseases and infections. Over the last 20 y, electrospray ionization mass spectrometry (ESI-MS) has emerged as a versatile tool for the identification and quantification of protein-ligand interactions in vitro. Here, we describe the implementation of the direct ESI-MS assay for the determination of protein-ligand binding stoichiometry and affinity. Additionally, we outline common sources of error encountered with these measurements and various strategies to overcome them. Finally, we comment on some of the outstanding challenges associated with the implementation of the assay and highlight new areas where direct ESI-MS measurements are expected to make significant contributions in the future.
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Affiliation(s)
- Elena N Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, T6G 2G2
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16
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Sterling HJ, Kintzer AF, Feld GK, Cassou CA, Krantz BA, Williams ER. Supercharging protein complexes from aqueous solution disrupts their native conformations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:191-200. [PMID: 22161509 PMCID: PMC3265691 DOI: 10.1007/s13361-011-0301-y] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 11/11/2011] [Accepted: 11/15/2011] [Indexed: 05/25/2023]
Abstract
The effects of aqueous solution supercharging on the solution- and gas-phase structures of two protein complexes were investigated using traveling-wave ion mobility-mass spectrometry (TWIMS-MS). Low initial concentrations of m-nitrobenzyl alcohol (m-NBA) in the electrospray ionization (ESI) solution can effectively increase the charge of concanavalin A dimers and tetramers, but at higher m-NBA concentrations, the increases in charge are accompanied by solution-phase dissociation of the dimers and up to a ~22% increase in the collision cross section (CCS) of the tetramers. With just 0.8% m-NBA added to the ESI solution of a ~630 kDa anthrax toxin octamer complex, the average charge is increased by only ~4% compared with the "native" complex, but it is sufficiently destabilized so that extensive gas-phase fragmentation occurs in the relatively high pressure regions of the TWIMS device. Anthrax toxin complexes exist in either a prechannel or a transmembrane channel state. With m-NBA, the prechannel state of the complex has the same CCS/charge ratio in the gas phase as the transmembrane channel state of the same complex formed without m-NBA, yet undergoes extensive dissociation, indicating that destabilization from supercharging occurs in the ESI droplet prior to ion formation and is not a result of Coulombic destabilization in the gas phase as a result of higher charging. These results demonstrate that the supercharging of large protein complexes is the result of conformational changes induced by the reagents in the ESI droplets, where enrichment of the supercharging reagent during droplet evaporation occurs.
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Affiliation(s)
- Harry J. Sterling
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Alexander F. Kintzer
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Geoffrey K. Feld
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Catherine A. Cassou
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Bryan A. Krantz
- Department of Chemistry, University of California, Berkeley, California 94720-1460
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-1460
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460
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17
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Sterling HJ, Cassou CA, Trnka MJ, Burlingame AL, Krantz BA, Williams ER. The role of conformational flexibility on protein supercharging in native electrospray ionization. Phys Chem Chem Phys 2011; 13:18288-96. [PMID: 21399817 PMCID: PMC3415327 DOI: 10.1039/c1cp20277d] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Effects of covalent intramolecular bonds, either native disulfide bridges or chemical crosslinks, on ESI supercharging of proteins from aqueous solutions were investigated. Chemically modifying cytochrome c with up to seven crosslinks or ubiquitin with up to two crosslinks did not affect the average or maximum charge states of these proteins in the absence of m-nitrobenzyl alcohol (m-NBA), but the extent of supercharging induced by m-NBA increased with decreasing numbers of crosslinks. For the model random coil polypeptide reduced/alkylated RNase A, a decrease in charging with increasing m-NBA concentration attributable to reduced surface tension of the ESI droplet was observed, whereas native RNase A electrosprayed from these same solutions exhibited enhanced charging. The inverse relationship between the extent of supercharging and the number of intramolecular crosslinks for folded proteins, as well as the absence of supercharging for proteins that are random coils in aqueous solution, indicate that conformational restrictions induced by the crosslinks reduce the extent of supercharging. These results provide additional evidence that protein and protein complex supercharging from aqueous solution is primarily due to partial or significant unfolding that occurs as a result of chemical and/or thermal denaturation induced by the supercharging reagent late in the ESI droplet lifetime.
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Affiliation(s)
- Harry J. Sterling
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Catherine A. Cassou
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Michael J. Trnka
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517
| | - A. L. Burlingame
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517
| | - Bryan A. Krantz
- Department of Chemistry, University of California, Berkeley, California 94720-1460
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-1460
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460
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18
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Nonresonant femtosecond laser vaporization of aqueous protein preserves folded structure. Proc Natl Acad Sci U S A 2011; 108:12217-22. [PMID: 21746908 DOI: 10.1073/pnas.1105673108] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Femtosecond laser vaporization-based mass spectrometry can be used to measure protein conformation in vitro at atmospheric pressure. Cytochrome c and lysozyme are vaporized from the condensed phase into the gas phase intact when exposed to an intense (10(13) W/cm(2)), nonresonant (800 nm), ultrafast (75 fs) laser pulse. Electrospray postionization time-of-flight mass spectrometry reveals that the vaporized protein maintains the solution-phase conformation through measurement of the charge-state distribution and the collision-induced dissociation channels.
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Sterling HJ, Prell JS, Cassou CA, Williams ER. Protein conformation and supercharging with DMSO from aqueous solution. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2011; 22:1178-86. [PMID: 21953100 PMCID: PMC3107942 DOI: 10.1007/s13361-011-0116-x] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 02/16/2011] [Accepted: 02/22/2011] [Indexed: 05/10/2023]
Abstract
The efficacy of dimethyl sulfoxide (DMSO) as a supercharging reagent for protein ions formed by electrospray ionization from aqueous solution and the mechanism for supercharging were investigated. Addition of small amounts of DMSO to aqueous solutions containing hen egg white lysozyme or equine myoglobin results in a lowering of charge, whereas a significant increase in charge occurs at higher concentrations. Results from both near-UV circular dichroism spectroscopy and solution-phase hydrogen/deuterium exchange mass spectrometry indicate that DMSO causes a compaction of the native structure of these proteins at low concentration, but significant unfolding occurs at ~63% and ~43% DMSO for lysozyme and myoglobin, respectively. The DMSO concentrations required to denature these two proteins in bulk solution are ~3-5 times higher than the concentrations required for the onset of supercharging, consistent with a significantly increased concentration of this high boiling point supercharging reagent in the ESI droplet as preferential evaporation of water occurs. DMSO is slightly more basic than m-nitrobenzyl alcohol and sulfolane, two other supercharging reagents, based on calculated proton affinity and gas-phase basicity values both at the B3LYP and MP2 levels of theory, and all three of these supercharging reagents are significantly more basic than water. These results provide additional evidence that the origin of supercharging from aqueous solution is the result of chemical and/or thermal denaturation that occurs in the ESI droplet as the concentration of these supercharging reagents increases, and that proton transfer reactivity does not play a significant role in the charge enhancement observed.
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Affiliation(s)
- Harry J. Sterling
- Department of Chemistry, University of California, Berkeley, CA 94720-1460 USA
| | - James S. Prell
- Department of Chemistry, University of California, Berkeley, CA 94720-1460 USA
| | - Catherine A. Cassou
- Department of Chemistry, University of California, Berkeley, CA 94720-1460 USA
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, CA 94720-1460 USA
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20
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He J, Tang F, Luo Z, Chen Y, Xu J, Zhang R, Wang X, Abliz Z. Air flow assisted ionization for remote sampling of ambient mass spectrometry and its application. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:843-850. [PMID: 21416520 DOI: 10.1002/rcm.4920] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 12/27/2010] [Accepted: 12/31/2010] [Indexed: 05/30/2023]
Abstract
Ambient ionization methods are an important research area in mass spectrometry (MS) analysis. Under ambient conditions, the gas flow and atmospheric pressure significantly affect the transfer and focusing of ions. The design and implementation of air flow assisted ionization (AFAI) as a novel and effective, remote sampling method for ambient mass spectrometry are described herein. AFAI benefits from a high extracting air flow rate. A systematic investigation of the extracting air flow in the AFAI system has been carried out, and it has been demonstrated not only that it plays a role in the effective capture and remote transport of charged droplets, but also that it promotes desolvation and ion formation, and even prevents ion fragmentation during the ionization process. Moreover, the sensitivity of remote sampling ambient MS analysis was improved significantly by the AFAI method. Highly polar and nonpolar molecules, including dyes, pharmaceutical samples, explosives, drugs of abuse, protein and volatile compounds, have been successfully analyzed using AFAI-MS. The successful application of the technique to residue detection on fingers, large object analysis and remote monitoring in real time indicates its potential for the analysis of a variety of samples, especially large objects. The ability to couple this technique with most commercially available MS instruments with an API interface further enhances its broad applicability.
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Affiliation(s)
- Jiuming He
- Key Laboratory of Bioactive Substances and Resource Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, PR China
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21
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Robichaud G, Dixon RB, Potturi AS, Cassidy D, Edwards JR, Sohn A, Dow TA, Muddiman DC. Design, Modeling, Fabrication, and Evaluation of the Air Amplifier for Improved Detection of Biomolecules by Electrospray Ionization Mass Spectrometry. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2011; 300:99-107. [PMID: 21499524 PMCID: PMC3076729 DOI: 10.1016/j.ijms.2010.04.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Through a multi-disciplinary approach, the air amplifier is being evolved as a highly engineered device to improve detection limits of biomolecules when using electrospray ionization. Several key aspects have driven the modifications to the device through experimentation and simulations. We have developed a computer simulation that accurately portrays actual conditions and the results from these simulations are corroborated by the experimental data. These computer simulations can be used to predict outcomes from future designs resulting in a design process that is efficient in terms of financial cost and time. We have fabricated a new device with annular gap control over a range of 50 to 70 μm using piezoelectric actuators. This has enabled us to obtain better aerodynamic performance when compared to the previous design (2× more vacuum) and also more reproducible results. This is allowing us to study a broader experimental space than the previous design which is critical in guiding future directions. This work also presents and explains the principles behind a fractional factorial design of experiments methodology for testing a large number of experimental parameters in an orderly and efficient manner to understand and optimize the critical parameters that lead to obtain improved detection limits while minimizing the number of experiments performed. Preliminary results showed that several folds of improvements could be obtained for certain condition of operations (up to 34 folds).
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Affiliation(s)
- Guillaume Robichaud
- Precision Engineering Center, North Carolina State University, Raleigh, North Carolina 27695
| | - R. Brent Dixon
- Chemistry, W.M. Keck FT-ICR Mass Spectrometry Laboratory, North Carolina State University, Raleigh, North Carolina 27695
| | - Amarnatha S. Potturi
- Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695
| | - Dan Cassidy
- Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695
| | - Jack R. Edwards
- Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695
| | - Alex Sohn
- Precision Engineering Center, North Carolina State University, Raleigh, North Carolina 27695
| | - Thomas A. Dow
- Precision Engineering Center, North Carolina State University, Raleigh, North Carolina 27695
| | - David C. Muddiman
- Chemistry, W.M. Keck FT-ICR Mass Spectrometry Laboratory, North Carolina State University, Raleigh, North Carolina 27695
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22
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Erba EB, Zenobi R. Mass spectrometric studies of dissociation constants of noncovalent complexes. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1pc90006d] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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23
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Song Q, Xu W, Smith SA, Gao L, Chappell WJ, Cooks RG, Ouyang Z. Ion trap mass analysis at high pressure: an experimental characterization. JOURNAL OF MASS SPECTROMETRY : JMS 2010; 45:26-34. [PMID: 19862776 DOI: 10.1002/jms.1684] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In recent years, it has become increasingly interesting to understand the performance of mass spectrometers at pressures much higher than those employed with conventional operating conditions. This interest has been driven by several influences, including demand for the development of reduced-power miniature mass spectrometers, desire for improved ion transfer into and through mass spectrometers, enhanced-yield preparative mass separations, and mass filtering at the atmospheric pressure interface. In this study, an instrument was configured to allow for the performance characterization of a rectilinear ion trap (RIT) at pressures up to 50 mtorr with air used as the buffer gas. The mass analysis efficiency, mass resolution, isolation efficiency, and collision-induced dissociation (CID) efficiency were evaluated at pressures ranging from 1 to 50 mtorr. The extent of degradation of mass resolution, isolation efficiency and ion stability as functions of pressure were characterized. Also, the optimal resonance ejection conditions were obtained at various pressures. Operations at 50 mtorr demonstrated improved CID efficiency in addition to peak widths of 2 and 5 m/z units (full width at half-maximum, FWHM) for protonated caffeine (m/z 195) and Ultramark (m/z 1521) respectively.
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Affiliation(s)
- Qingyu Song
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA
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24
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Guo N, Zhang R, Song F, He J, Xia B, Abliz Z. Characterization of acid-induced protein conformational changes and noncovalent complexes in solution by using coldspray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2009; 20:845-851. [PMID: 19211263 DOI: 10.1016/j.jasms.2008.12.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/23/2008] [Accepted: 12/24/2008] [Indexed: 05/27/2023]
Abstract
Coldspray ionization (CSI) mass spectrometry, a variant of electrospray ionization (ESI) operating at low temperature (20 to -80 degrees C), has been used to characterize protein conformation and noncovalent complexes. A comparison of CSI and ESI was presented for the investigation of the equilibrium acid-induced unfolding of cytochrome c, ubiquitin, myoglobin, and cyclophilin A (CypA) over a wide range of pH values in aqueous solutions. CSI and nanoelectrospray ionization (nanoESI) were also compared in their performance to characterize the conformational changes of cytochrome c and myoglobin. Significant differences were observed, with narrower charged-state distribution and a shift to lower charge state in the CSI mass spectra compared with those in ESI and nanoESI mass spectra. The results suggest that CSI is more prone to preserving folded protein conformations in solution than the ESI and nanoESI methods. Moreover, the CSI-MS data are comparable with those obtained by other established biophysical methods, which are generally acknowledged to be the suitable techniques for monitoring protein conformation in solution. Noncovalent complexes of holomyoglobin and the protein-ligand complex between CypA and cyclosporin A (CsA) were also investigated at a neutral pH using the CSI-MS method. The results of this study suggest the ability of CSI-MS in retaining of protein conformation and noncovalent interactions in solution and probing subtle protein conformational changes. Additionally, the CSI-MS method is capable of analyzing quantitatively equilibrium unfolding transitions of proteins. CSI-MS may become one of the promising techniques for investigating protein conformation and noncovalent protein-ligand interactions in solution.
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Affiliation(s)
- Na Guo
- Key Laboratory of Bioactive Substances and Resource Utilization of Chinese Herbal Medicine, Ministry of Education, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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25
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Rapp E, Charvát A, Beinsen A, Plessmann U, Reichl U, Seidel-Morgenstern A, Urlaub H, Abel B. Atmospheric pressure free liquid infrared MALDI mass spectrometry: toward a combined ESI/ MALDI-liquid chromatography interface. Anal Chem 2009; 81:443-52. [PMID: 19125446 DOI: 10.1021/ac801863p] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A new atmospheric pressure (AP)-MALDI-type interface has been developed based on a free liquid (FL) microbeam/microdroplets and a mid-infrared optical parametric oscillator (mid-IR OPO). The device is integrated into a standard on-line nanoESI interface. The generation of molecular ions in the gas phase is believed to be the result of a fast (explosive) laser-induced evaporative dispersion(not desorption) of the microbeam into statistically charged nanodroplets. Only the lowest charge states appear insignificant abundance in this type of experiment. Mass spectra of some common peptides have been acquired in positive ion mode, and the limit-of-detection of this first prototype (liquid microbeam setup) was evaluated to be 17 fmol per second. To improve the duty cycle and to reduce the sample consumption, a droplet-on-demand system was implemented (generating 100 pL droplets).With this setup, about 20 attomole of bradykinin were sufficient to achieve a signal-to-noise ratio better than five.This setup can be operated at flow rates down to 100 nL/min and represents a liquid MALDI alternative to the nanoESI. Our particular interest was the application of the developed ion source for on-line coupling of liquid chromatography with mass spectrometry. The flow rates(>100 microL/min), required for stable operation of the ion source in continuous liquid microbeam mode, matches perfectly the flow rate range of micro HPLC. Therefore, online LC/MS experiments have been realized, employing a microbore C18 reversed-phase column to separate an artificial peptide mixture and tryptic peptides of bovine serum albumin (performing a peptide mass fingerprint). In the latter case, sequence coverage of more than 90%has been achieved.
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Affiliation(s)
- Erdmann Rapp
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany.
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26
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Hogan CJ, Carroll JA, Rohrs HW, Biswas P, Gross ML. Combined charged residue-field emission model of macromolecular electrospray ionization. Anal Chem 2009; 81:369-77. [PMID: 19117463 PMCID: PMC2613577 DOI: 10.1021/ac8016532] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of the multiple charging of macromolecules in electrospray ionization (ESI) continues to inspire debate and controversy. Recently, we proposed that the number of charges on a macromolecule is determined by the emission of small charge carriers from macromolecule-containing nanodroplets and that, after solvent evaporation, the remaining charge is transferred to the macromolecule. In this study, we tested the applicability of this new theory for macromolecular, positive-ion ESI mass spectrometry by measuring the mean charge states and charge distributions of globular proteins under non-denaturing and denaturing conditions. Predictions of protein mean charge states for native state proteins are in excellent agreement with mass spectrometric measurements, giving strong credence to the proposed theory. Theoretical predictions are also in good agreement with mean charge states measured for proteins in basic solutions (pH = 11.5). For some proteins in acidic solutions (pH = 2.1), the measured mean charge states are anomalously higher than the Rayleigh limit of a water droplet with a volume equivalent to that of the protein. We propose that some macromolecules that are highly charged in solution may desorb from charged droplets of the same polarity in a similar manner to that whereby charge carriers emit from nanodroplets, leading to "supercharged" macromolecular ions. Examination of rate expressions for solvent evaporation and charge-carrier emission demonstrates that the newly proposed model for ESI is consistent with previously reported ion-emission kinetics. Overall, we obtained additional experimental evidence for the charge carrier emission model for macromolecular charging, suggesting opportunities for understanding and applying ESI-MS.
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Affiliation(s)
- Christopher J Hogan
- Department of Energy, Environmental, & Chemical Engineering, Washington University in St. Louis, Saint Louis, Missouri 63130, USA.
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27
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Hampton CY, Silvestri CJ, Forbes TP, Varady MJ, Meacham JM, Fedorov AG, Degertekin FL, Fernández FM. Comparison of the internal energy deposition of Venturi-assisted electrospray ionization and a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE). JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:1320-9. [PMID: 18650100 PMCID: PMC2563429 DOI: 10.1016/j.jasms.2008.06.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/19/2008] [Accepted: 06/19/2008] [Indexed: 05/12/2023]
Abstract
The internal energy deposition of a Venturi-assisted array of micromachined ultrasonic electrosprays (AMUSE), with and without the application of a DC charging potential, is compared with equivalent experiments for Venturi-assisted electrospray ionization (ESI) using the "survival yield" method on a series of para-substituted benzylpyridinium salts. Under conditions previously shown to provide maximum ion yields for standard compounds, the observed mean internal energies were nearly identical (1.93-2.01 eV). Operation of AMUSE without nitrogen flow to sustain the air amplifier focusing effect generated energetically colder ions with mean internal energies that were up to 39% lower than those for ESI. A balance between improved ion transfer, adequate desolvation, and favorable ion energetics was achieved by selection of optimum operational ranges for the parameters that most strongly influence the ion population: the air amplifier gas flow rate and API capillary temperature. Examination of the energy landscapes obtained for combinations of these parameters showed that a low internal energy region (<or=1.0 eV) was present at nitrogen flow rates between 2 and 4 L min(-1) and capillary temperatures up to 250 degrees C using ESI (9% of all parameter combinations tested). Using AMUSE, this region was present at nitrogen flow rates up to 2.5 L min(-1) and all capillary temperatures (13% of combinations tested). The signal-to-noise (S/N) ratio of the intact p-methylbenzylpyridinium ion obtained from a 5 microM mixture of thermometer compounds using AMUSE at the extremes of the studied temperature range was at least fivefold higher than that of ESI, demonstrating the potential of AMUSE ionization as a soft method for the characterization of labile species by mass spectrometry.
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Affiliation(s)
- Christina Y. Hampton
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Catherine J. Silvestri
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Thomas P. Forbes
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Mark J. Varady
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - J. Mark Meacham
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Andrei G. Fedorov
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332
| | - F. Levent Degertekin
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Facundo M. Fernández
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
- Address reprint requests to Facundo M. Fernández, Ph.D. 901 Atlantic Dr. NW. Atlanta, GA 30332-0400., Phone: 404-385-4432, Fax: 404-385-6447,
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28
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Dixon RB, Sampson JS, Hawkridge AM, Muddiman DC. Ambient Aerodynamic Ionization Source for Remote Analyte Sampling and Mass Spectrometric Analysis. Anal Chem 2008; 80:5266-71. [DOI: 10.1021/ac800289f] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- R. Brent Dixon
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - Jason S. Sampson
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - Adam M. Hawkridge
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - David C. Muddiman
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
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29
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Harris GA, Nyadong L, Fernandez FM. Recent developments in ambient ionization techniques for analytical mass spectrometry. Analyst 2008; 133:1297-301. [DOI: 10.1039/b806810k] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Hampton CY, Forbes TP, Varady MJ, Meacham JM, Fedorov AG, Degertekin FL, Fernández FM. Analytical performance of a venturi-assisted array of micromachined ultrasonic electrosprays coupled to ion trap mass spectrometry for the analysis of peptides and proteins. Anal Chem 2007; 79:8154-61. [PMID: 17914864 PMCID: PMC2543123 DOI: 10.1021/ac071297n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The analytical characterization of a novel ion source for mass spectrometry named array of micromachined ultrasonic electrosprays (AMUSE) is presented here. This is a fundamentally different type of ion generation device, consisting of three major components: (1) a piezoelectric transducer that creates ultrasonic waves at one of the resonant frequencies of the sample-filled device, (2) an array of pyramidally shaped nozzles micromachined on a silicon wafer, and (3) a spacer which prevents contact between the array and transducer ensuring the transfer of acoustic energy to the sample. A high-pressure gradient generated at the apexes of the nozzle pyramids forces the periodic ejection of multiple droplet streams from the device. With this device, the processes of droplet formation and droplet charging are separated; hence, the limitations of conventional electrospray-type ion sources, including the need for high charging potentials and the addition of organic solvent to decrease surface tension, can be avoided. In this work, a Venturi device is coupled with AMUSE in order to increase desolvation, droplet focusing, and signal stability. Results show that ionization of model peptides and small tuning molecules is possible with dc charging potentials of 100 Vdc or less. Ionization in rf-only mode (without dc biasing) was also possible. It was observed that, when combined with AMUSE, the Venturi device provides a 10-fold gain in signal-to-noise ratio for 90% aqueous sample solutions. Further reduction in the diameter of the orifices of the micromachined arrays led to an additional signal gain of at least 3 orders of magnitude, a 2-10-fold gain in the signal-to-noise ratio and an improvement in signal stability from 47% to 8.5% RSD. The effectiveness of this device for the soft ionization of model proteins in aqueous media, such as cytochrome c, was also examined, yielding spectra with an average charge state of 8.8 when analyzed with a 100 Vdc charging potential. Ionization of model proteins was also possible in rf-only mode.
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Affiliation(s)
- Christina Y. Hampton
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Thomas P. Forbes
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Mark J. Varady
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - J. Mark Meacham
- Biochemical Sciences Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Andrei G. Fedorov
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
- Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332
| | - F. Levent Degertekin
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Facundo M. Fernández
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332
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31
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Dixon RB, Muddiman DC, Hawkridge AM, Fedorov AG. Probing the mechanisms of an air amplifier using a LTQ-FT-ICR-MS and fluorescence spectroscopy. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2007; 18:1909-13. [PMID: 17855111 PMCID: PMC2426928 DOI: 10.1016/j.jasms.2007.08.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 08/09/2007] [Accepted: 08/10/2007] [Indexed: 05/12/2023]
Abstract
We report the first quantitative assessment of electrosprayed droplet/ion focusing enabled by the use of a voltage-assisted air amplifier between an electrospray ionization emitter and a hybrid linear ion trap Fourier transform ion cyclotron resonance mass spectrometer (ESI-LTQ-FT-ICR-MS). A solution of fluorescent dye was electrosprayed with a stainless steel mesh screen placed in front of the MS inlet capillary acting as a gas-permeable imaging plate for fluorescence spectroscopy. Without use of the air amplifier, no detectable FT-ICR signal was observed, as well as no detectable fluorescence on the screen upon imaging using a fluorescence scanner. When the air amplifier was turned ON while electrospraying the fluorescent dye, FT-ICR mass spectra with high signal to noise ratio were obtained with an average ion injection time of 21 ms for an AGC target value of 5 x 10(5). Imaging of the screen using a fluorescence scanner produced a distinct spot of cross-sectional area approximately 33.5 mm(2) in front of the MS inlet capillary. These experimental results provide direct evidence of aerodynamic focusing of electrosprayed droplets/ions enabled by an air amplifier, resulting in improved electrospray droplet/ion capture efficiency and reduced ion injection time. A second set of experiments was carried out to explore whether the air amplifier assists in desolvation. By electrospraying a mix of quaternary amines, ratios of increasingly hydrophobic molecules were obtained. Observation of the solvophobic effect associated with electrospray ionization resulted in a higher abundance of the hydrophobic molecule. This bias was eliminated when the air amplifier was turned ON and a response indicative of the respective component concentrations of the molecules in the bulk solution was observed.
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Affiliation(s)
- R. Brent Dixon
- W.M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - David C. Muddiman
- W.M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
- *Author for Correspondence: David C. Muddiman, Ph.D., W.M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, Phone: 919-513-0084, Fax: 919-513-7993,
| | - Adam M. Hawkridge
- W.M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695
| | - A. G. Fedorov
- G.W. Woodruff School of Mechanical Engineering and Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
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32
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Dixon RB, Bereman MS, Muddiman DC, Hawkridge AM. Remote mass spectrometric sampling of electrospray- and desorption electrospray-generated ions using an air ejector. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2007; 18:1844-7. [PMID: 17716909 PMCID: PMC2151844 DOI: 10.1016/j.jasms.2007.07.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 07/10/2007] [Accepted: 07/22/2007] [Indexed: 05/12/2023]
Abstract
A commercial air ejector was coupled to an electrospray ionization linear ion trap mass spectrometer (LTQ) to transport remotely generated ions from both electrospray (ESI) and desorption electrospray ionization (DESI) sources. We demonstrate the remote analysis of a series of analyte ions that range from small molecules and polymers to polypeptides using the AE-LTQ interface. The details of the ESI-AE-LTQ and DESI-AE-LTQ experimental configurations are described and preliminary mass spectrometric data are presented.
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Affiliation(s)
| | | | | | - Adam M. Hawkridge
- Author for Correspondence Adam Hawkridge, PhD., W.M Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, Phone: 919-513-7947, Fax: 919-513-7993,
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33
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Na N, Zhao M, Zhang S, Yang C, Zhang X. Development of a dielectric barrier discharge ion source for ambient mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2007; 18:1859-62. [PMID: 17728138 DOI: 10.1016/j.jasms.2007.07.027] [Citation(s) in RCA: 295] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 07/14/2007] [Accepted: 07/24/2007] [Indexed: 05/17/2023]
Abstract
A new ion source based on dielectric barrier discharge was developed as an alternative ionization source for ambient mass spectrometry. The dielectric barrier discharge ionization source, termed as DBDI herein, was composed of a copper sheet electrode, a discharge electrode, and a piece of glass slide in between as dielectric barrier as well as sample plate. Stable low-temperature plasma was formed between the tip of the discharge electrode and the surface of glass slide when an alternating voltage was applied between the electrodes. Analytes deposited on the surface of the glass slide were desorbed and ionized by the plasma and the ions were introduced to the mass spectrometer for mass analysis. The capability of this new ambient ion source was demonstrated with the analysis of 20 amino acids, which were deposited on the glass slide separately. Protonated molecular ions of [M + H](+) were observed for all the amino acids except for L-arginine. This ion source was also used for a rapid discrimination of L-valine, L-proline, L-serine and L-alanine from their mixture. The limit of detection was 3.5 pmol for L-alanine using single-ion-monitoring (SIM). Relative standard deviation (RSD) was 5.78% for 17.5 nmol of L-alanine (n = 5). With the advantages of small size, simple configuration and ease operation at ambient conditions, the dielectric barrier discharge ion source would potentially be coupled to portable mass spectrometers.
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Affiliation(s)
- Na Na
- Department of Chemistry, Key Laboratory for Atomic and Molecular Nanosciences of Education Ministry, Tsinghua University, Beijing, China
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Dixon RB, Muddiman DC. Quantitative comparison of a flared and a standard heated metal capillary inlet with a voltage-assisted air amplifier on an electrospray ionization linear ion trap mass spectrometer. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:3207-12. [PMID: 17764103 DOI: 10.1002/rcm.3206] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The performance characteristics (i.e., ion abundance and electrospray ion current) of a flared and blunt-ended heated metal capillary were evaluated with a voltage-assisted air amplifier on a linear ion trap mass spectrometer (LTQ-MS). The results demonstrated that a standard capillary afforded higher ion abundance than a flared capillary, thus further work is necessary to investigate conditions for which significant benefits with the flared capillary will be observed. The compatibility of a voltage-assisted air amplifier is explored for both types of capillaries and in all cases resulted in improved ion abundance and spray current.
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Affiliation(s)
- R Brent Dixon
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
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Sampson JS, Hawkridge AM, Muddiman DC. Direct characterization of intact polypeptides by matrix-assisted laser desorption electrospray ionization quadrupole Fourier transform ion cyclotron resonance mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:1150-4. [PMID: 17318926 DOI: 10.1002/rcm.2947] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We report the characterization of a recently introduced hybrid ionization source, matrix-assisted laser desorption electrospray ionization (MALDESI), coupled to a quadrupole Fourier transform ion cyclotron resonance mass spectrometry (QFT-ICR-MS) system. We first demonstrate the ability of MALDESI-QFT-ICR MS to directly analyze and provide high mass measurement accuracy (approximately 1 part-per-million) of a polypeptide using internal calibration. Second, we show the potential of MALDESI-QFT-ICR MS for the top-down characterization of multiply charged polypeptide cations. Finally, we demonstrate sub-femtomole detection limits in MALDESI-QFT-ICR MS using a combination of naturally occurring peptides and their respective stable isotope labeled forms. The results presented herein demonstrate the feasibility of several potential applications for MALDESI-QFT-ICR MS for the direct analysis of intact biological molecules.
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Affiliation(s)
- Jason S Sampson
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
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Sampson JS, Hawkridge AM, Muddiman DC. Generation and detection of multiply-charged peptides and proteins by matrix-assisted laser desorption electrospray ionization (MALDESI) Fourier transform ion cyclotron resonance mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1712-6. [PMID: 16952462 DOI: 10.1016/j.jasms.2006.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2006] [Revised: 08/06/2006] [Accepted: 08/07/2006] [Indexed: 05/03/2023]
Abstract
We report the coupling of a hybrid ionization source, matrix-assisted laser desorption electrospray ionization (MALDESI), to a Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS). The details of the source design and initial data are presented. Analysis of peptides and proteins ranging from 1 to 8.6 kDa resulted in high resolving power single-acquisition FT-ICR mass spectra with average charge-states highly correlated to those obtained by nanoESI, thus, providing strong evidence that the ESI process dictates the observed charge-state distribution. Importantly, unlike the recently introduced electrospray assisted laser desorption ionization (ELDI) source reported by Shiea and coworkers [1, 2], the data we have obtained to date rely on the use of an organic acid matrix. The results presented herein provide insight into the charging mechanism of this emerging ionization approach, while also expanding the utility of FT-ICR MS for top-down protein and complex mixture analysis.
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Affiliation(s)
- Jason S Sampson
- W. M. Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, USA
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37
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Ibrahim Y, Tang K, Tolmachev AV, Shvartsburg AA, Smith RD. Improving mass spectrometer sensitivity using a high-pressure electrodynamic ion funnel interface. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1299-305. [PMID: 16839773 PMCID: PMC1785296 DOI: 10.1016/j.jasms.2006.06.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 06/08/2006] [Accepted: 06/09/2006] [Indexed: 05/10/2023]
Abstract
We report on a new electrodynamic ion funnel that operates at a pressure of 30 torr with no loss of ion transmission. The enhanced performance compared with previous ion funnel designs optimized for pressures of <5 torr was achieved by reducing the ion funnel capacitance and increasing the RF drive frequency (1.7 MHz) and amplitude (100-170 V peak-to-peak). No degradation of ion transmission was observed for pressures from 2 to 30 torr. The ability to operate at higher pressure enabled a new tandem ion funnel mass spectrometer interface design that can accommodate a greater gas load (e.g., from an ESI source). When combined with a multicapillary inlet, the interface provided more efficient introduction of ions, resulting in a significant enhancement in mass spectrometer sensitivity and detection limits.
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Affiliation(s)
- Yehia Ibrahim
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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38
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Benesch JLP, Robinson CV. Mass spectrometry of macromolecular assemblies: preservation and dissociation. Curr Opin Struct Biol 2006; 16:245-51. [PMID: 16563743 DOI: 10.1016/j.sbi.2006.03.009] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 02/06/2006] [Accepted: 03/14/2006] [Indexed: 11/16/2022]
Abstract
Mass spectrometry not only plays a crucial role in the identification of proteins involved in the intricate interaction networks of the cell, but also is increasingly involved in the characterization of the non-covalent complexes formed by interacting partners. Recent developments have enabled the use of gas phase dissociation to probe oligomeric organization and topology, and increased understanding of the electrospray process is leading to knowledge of the structure of protein assemblies both in solution and in the gas phase.
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Affiliation(s)
- Justin L P Benesch
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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Bereman MS, Nyadong L, Fernandez FM, Muddiman DC. Direct high-resolution peptide and protein analysis by desorption electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2006; 20:3409-11. [PMID: 17051610 DOI: 10.1002/rcm.2759] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We report the first coupling of a desorption electrospray ionization (DESI) ion source to Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) for high-resolution protein analysis. The DESI FT-ICR-MS source design is described in detail along with preliminary data obtained on peptides and proteins ranging from 1 to 5.7 kDa.
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Affiliation(s)
- Michael S Bereman
- W M Keck FT-ICR Mass Spectrometry Laboratory, Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
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