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Gas-Phase H/D Exchange and Collision Cross Sections of Hemoglobin Monomers, Dimers, and Tetramers

TitleGas-Phase H/D Exchange and Collision Cross Sections of Hemoglobin Monomers, Dimers, and Tetramers
Publication TypeJournal Article
Year of Publication2009
AuthorsWright, PJ, Douglas, DJ
JournalJournal of the American Society for Mass Spectrometry
Volume20
Pagination484-495
Date PublishedMar
Type of ArticleArticle
ISBN Number1044-0305
KeywordsACID-INDUCED DENATURATION, CYTOCHROME-C IONS, DIFFERENT SOLUTION CONFORMATIONS, ELECTROSPRAY MASS-SPECTROMETRY, EXCHANGE, GLOBIN CHAINS, HYDROGEN/DEUTERIUM, ION-TRAP, MYOGLOBIN IONS, noncovalent protein complexes, OF-FLIGHT SYSTEM, QUADRUPOLE
Abstract

The conformations of gas-phase ions of hemoglobin, and its dimer and monomer subunits have been studied with H/D exchange and cross section measurements. During the H/D exchange measurements, tetramers undergo slow dissociation to dimers, and dimers to monomers, but this did not prevent drawing conclusions about the relative exchange levels of monomers, dimers, and tetramers. Assembly of the monomers into tetramers, hexamers, and octamers causes the monomers to exchange a greater fraction of their hydrogens. Dimer ions, however, exchange a lower fraction of their hydrogens than monomers or tetramers. Solvation of tetramers affects the exchange kinetics. Solvation molecules do not appear to exchange, and solvation lowers the overall exchange level of the tetramers. Cross section measurements show that monomer ions in low charge states, and tetramer ions have compact structures, comparable in size to the native conformations in solution. Dimers have remarkably compact structures, considerably smaller than the native conformation in solution and smaller than might be expected from the monomer or tetramer cross sections. This is consistent with the relatively low level of exchange of the dimers. (J Am Soc Mass Spectrom 2009, 20, 484-495) (C) 2009 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry

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