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Conformations of gas-phase lysozyme ions produced from two different solution conformations

TitleConformations of gas-phase lysozyme ions produced from two different solution conformations
Publication TypeJournal Article
Year of Publication2003
AuthorsMao, DM, Babu, KR, Chen, YL, Douglas, DJ
JournalAnalytical Chemistry
Volume75
Pagination1325-1330
Date PublishedMar
Type of ArticleArticle
ISBN Number0003-2700
KeywordsCOLLISION, CROSS-SECTIONS, CYTOCHROME-C, EGG-WHITE LYSOZYME, H/D EXCHANGE, HYDROGEN-DEUTERIUM EXCHANGE, HYDROGEN/DEUTERIUM EXCHANGE, IONIZATION MASS-SPECTROMETRY, IONS, OF-FLIGHT SYSTEM, PROTEIN, UNFOLDING DYNAMICS
Abstract

Near pH 2.0, lysozyme in water is in its native conformation, and in water/methanol (2/8) it adopts a helical denatured conformation (Kamatari et al. Protein Sci. 1998, 7, 681-688). Hydrogen/deuterium (H/D) exchange of lysozyme in solution confirms that it is partially unfolded at pH 2.0 in water/methanol (v/v = 2/8). With electrospray ionization (ESI) mass spectrometry (MS), lysozyme in water produces ions with charges +7 to +12, with the greatest intensity at +10, whereas lysozyme in water/methanol (2/8) produces ions with charges +6 to +12 with the greatest intensity at +7. Thus, lysozyme is an exception to the rule that a protein denatured in solution forms higher charge states than the same protein in its folded native conformations in solution. Because the same charge states are produced from these two solution conformations, a direct comparison of the properties of the gas-phase ions produced from two very different solution conformations is possible. The conformations of lysozyme ions in the gas phase were studied using cross section measurements and gas-phase H/D exchange. Similar cross sections and H/D exchange levels were observed for same-charge states of lysozyme ions formed from the native and helical denatured conformations in solution. Cross sections show that the ions have compact structures. Thus, disulfide-intact gaseous lysozyme ions generated from the denatured state in water/methanol (2/8) refold into compact structures in the gas phase on a time scale of milliseconds or less.

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