Abstract
At low pH in solutions of 50% methanol, proteins form expanded denatured states (the “H” state). In 90% methanol, proteins form expanded helical denatured states with artificial α-helices (the “Hc” state). Gas-phase ions of ubiquitin, cytochrome c, apomyoglobin, and native and disulfide-reduced β-lactoglobulin were formed by electrospray ionization (ESI) of the proteins from the H and Hc states in solution. Both states in solution produce the same charge states in ESI. The conformations of the ions were studied with cross section measurements and gas-phase H/D exchange experiments. The cross sections show that the ions retain considerable folded structure. For a given protein and given charge state, ions produced from the H and Hc states showed the same cross sections (within ∼1%). Ions of cytochrome c, apomyoglobin, and native and reduced β-lactoglobulin of a given charge state showed no differences in H/D exchange level when produced from the H or Hc state. However, ubiquitin ions produced from the Hc state consistently exchange fewer (∼13%) hydrogens than ions produced from the H state, suggesting that in this case the gas-phase protein ions retain some memory of their solution conformations.
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Published online July 24, 2008
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Wright, P.J., Zhang, J. & Douglas, D.J. Conformations of gas-phase ions of ubiquitin, cytochrome c, apomyoglobin, and β-lactoglobulin produced from two different solution conformations. J Am Soc Mass Spectrom 19, 1906–1913 (2008). https://doi.org/10.1016/j.jasms.2008.07.018
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DOI: https://doi.org/10.1016/j.jasms.2008.07.018