Structural Stability from Solution to the Gas Phase: Native Solution Structure of Ubiquitin Survives Analysis in a Solvent-Free Ion Mobility–Mass Spectrometry Environment

Thomas Wyttenbach and Michael T. Bowers*
Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
J. Phys. Chem. B, 2011, 115 (42), pp 12266–12275
DOI: 10.1021/jp206867a
Publication Date (Web): September 9, 2011
Copyright © 2011 American Chemical Society

Abstract

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The conformations of desolvated ubiquitin ions, lifted into the gas phase by electrospray ionization (ESI), were characterized by ion mobility spectrometry (IMS) and compared to the solution structures they originated from. The IMS instrument combining a two-meter helium drift tube with a quadrupole time-of-flight mass spectrometer was built in-house. Solutions stabilizing the native state of ubiquitin yielded essentially one family of tightly folded desolvated ubiquitin structures with a cross section matching the size of the native state (1000 Å2). Solutions favoring the A state yielded several well-defined families of significantly unfolded conformations (1800–2000 Å2) matching in size conformations between the A state and a fully unfolded state. On the basis of these results and a wealth of data available in the literature, we conclude that the native state of ubiquitin is preserved in the transition from solution to the desolvated state during the ESI process and survives for >100 ms in a 294 K solvent-free environment. The A state, however, is charged more extensively than the native state during ESI and decays more rapidly following ESI. A state ions unfold on a time scale equal to or shorter than the experiment (≤50 ms) to more extended structures.

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History

  • Published In Issue October 27, 2011
  • Article ASAPSeptember 30, 2011
  • Just Accepted ManuscriptSeptember 09, 2011
  • Received: July 18, 2011
    Revised: August 31, 2011

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