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

Eur. J. Mass Spectrom. 8, 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

ABSTRACT:

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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