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European Journal of Mass Spectrometry
Volume 8 Issue 2, Pages 177–180 (2002)
doi: 10.1255/ejms.487

Hydrogen atom loss in electron-capture dissociation: a Fourier transform-ion cyclotron resonance study with single isotopomeric ubiquitin ions

Kathrin Breuker, HanBin Oh, Blas A. Cerda, David M. Horn and Fred W. McLafferty*
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301, USA

In electron-capture dissociation (ECD), a multiply-protonated protein ion, trapped in a Fourier transform-ion cyclotron resonance (FT-ICR) cell, captures a low-energy electron at a protonated site. In a major reaction pathway, the resulting hydrogen atom attacks a backbone carbonyl oxygen to form a hypervalent species that immediately dissociates into a complementary c, z ion pair. For larger proteins, the reduced odd-electron ion (M + nH)(n – 1)+• is a major product, as shown here using isotopically isolated precursors. In addition, a hydrogen atom can be lost without further reaction, yielding the [M + (n – 1)H](n – 1)+ even-electron ions. The large effect of charge state on the yield of these ions suggests that the 9+ to 11+ charge states have novel charge-solvated secondary structures.

Keywords: ubiquitin, electron-capture dissociation, Fourier transform-ion cyclotron resonance, conformation

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