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Title: Charging of Proteins in Native Mass Spectrometry

Abstract

Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo proton transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the proteinmore » ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism.« less

Authors:
 [1];  [1];  [2];  [3];  [1]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry
  2. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Biophysics and Integrated Bioimaging Division; Univ. of Texas, Houston, TX (United States). M.D. Anderson Cancer Center, Dept. of Molecular and Cellular Oncology
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Institutes of Health (NIH)
OSTI Identifier:
1421799
Grant/Contract Number:  
AC02-05CH11231; R01GM097357
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Society for Mass Spectrometry
Additional Journal Information:
Journal Volume: 28; Journal Issue: 2; Journal ID: ISSN 1044-0305
Publisher:
American Society for Mass Spectrometry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Native mass spectrometry; ESI; Electrospray; Native ESI; Native mass spec; Native MS; Native electrospray; Electrospray ionization; Ammonium; Charging; Salts; Rayleigh limit; Charged residue mechanism; Gas-phase basicity; Apparent gas-phase basicity; Proton transfer; Combined charged residue-field emission model; Ion mobility; Circular dichroism; Mechanism; Charging mechanism; Protein ion charging

Citation Formats

Susa, Anna C., Xia, Zijie, Tang, Henry Y. H., Tainer, John A., and Williams, Evan R. Charging of Proteins in Native Mass Spectrometry. United States: N. p., 2016. Web. doi:10.1007/s13361-016-1517-7.
Susa, Anna C., Xia, Zijie, Tang, Henry Y. H., Tainer, John A., & Williams, Evan R. Charging of Proteins in Native Mass Spectrometry. United States. doi:10.1007/s13361-016-1517-7.
Susa, Anna C., Xia, Zijie, Tang, Henry Y. H., Tainer, John A., and Williams, Evan R. Wed . "Charging of Proteins in Native Mass Spectrometry". United States. doi:10.1007/s13361-016-1517-7. https://www.osti.gov/servlets/purl/1421799.
@article{osti_1421799,
title = {Charging of Proteins in Native Mass Spectrometry},
author = {Susa, Anna C. and Xia, Zijie and Tang, Henry Y. H. and Tainer, John A. and Williams, Evan R.},
abstractNote = {Factors that influence the charging of protein ions formed by electrospray ionization from aqueous solutions in which proteins have native structures and function were investigated. Protein ions ranging in molecular weight from 12.3 to 79.7 kDa and pI values from 5.4 to 9.6 were formed from different solutions and reacted with volatile bases of gas-phase basicities higher than that of ammonia in the cell of a Fourier-transform ion cyclotron resonance mass spectrometer. The charge-state distribution of cytochrome c ions formed from aqueous ammonium or potassium acetate is the same. Moreover, ions formed from these two solutions do not undergo proton transfer to 2-fluoropyridine, which is 8 kcal/mol more basic than ammonia. These results provide compelling evidence that proton transfer between ammonia and protein ions does not limit protein ion charge in native electrospray ionization. Both circular dichroism and ion mobility measurements indicate that there are differences in conformations of proteins in pure water and aqueous ammonium acetate, and these differences can account for the difference in the extent of charging and proton-transfer reactivities of protein ions formed from these solutions. The extent of proton transfer of the protein ions with higher gas-phase basicity bases trends with how closely the protein ions are charged to the value predicted by the Rayleigh limit for spherical water droplets approximately the same size as the proteins. These results indicate that droplet charge limits protein ion charge in native mass spectrometry and are consistent with these ions being formed by the charged residue mechanism.},
doi = {10.1007/s13361-016-1517-7},
journal = {Journal of the American Society for Mass Spectrometry},
number = 2,
volume = 28,
place = {United States},
year = {2016},
month = {10}
}

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Works referenced in this record:

Electrospray ionization-principles and practice
journal, January 1990

  • Fenn, John B.; Mann, Matthias; Meng, Chin Kai
  • Mass Spectrometry Reviews, Vol. 9, Issue 1, p. 37-70
  • DOI: 10.1002/mas.1280090103

How Hofmeister ion interactions affect protein stability
journal, October 1996