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Using ellipsoids to model charge distributions in gas phase protein complex ion dissociation

TitleUsing ellipsoids to model charge distributions in gas phase protein complex ion dissociation
Publication TypeJournal Article
Year of Publication2004
AuthorsCsiszar, S, Thachuk, M
JournalCanadian Journal of Chemistry-Revue Canadienne De Chimie
Volume82
Pagination1736-1744
Date PublishedDec
Type of ArticleArticle
ISBN Number0008-4042
Keywordscharge asymmetry, CYTOCHROME-C, ELECTROSPRAY-IONIZATION, ellipsoid charge model, EXCHANGE, IONIZATION MASS-SPECTROMETRY, ORIGIN, protein complex dissociation
Abstract

Gas phase protein complex dissociation was modelled using ellipsoids on which discrete charges were placed in randomly chosen charge sites. A number of sizes, shapes, orientations, and types of ellipsoids were considered. For each case, charge transfer parameters and electrostatic energies were calculated as a function of the fractional surface area. It was found that to within 10-15%, the charge on product ions after dissociation is distributed according to their fractional surface area. This can imply, for example, that in experiments measuring the dissociation of homodimers, charge asymmetries of greater than 10-15% in the product ions signal that one of the ions has greatly increased its surface area, such as would occur with unfolding. This assumes that proton transfer occurs on a timescale fast enough that the dissociation products adopt the minimum electrostatic energy configuration. Calculation of this energy shows that it is minimized when one or more of the monomers is in an extended conformation.

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