Models of fragmentations induced by electron attachment to protonated peptides

Eur. J. Mass Spectrom. 10, 625–638 (2004)
DOI: 10.1255/ejms.665

Models of fragmentations induced by electron attachment to protonated peptides

Vebjørn Bakken, Trygve Helgaker and Einar Uggerud^*
Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway. E-mail: einar.uggerud@kjemi.uio.no

ABSTRACT:

Invoking a number of theoretical levels ranging from HF/STO-3G to CCSD(T)/aug-cc-pVQZ, we have made a detailed survey of six potential energy surfaces (NH₄⁺, NH₄^·, [CH₃CONHCH₃]H⁺, [CH₃CONHCH₃]H^·, [HCONHCH₂CONH₂]H⁺, [HCONHCH₂CONH₂]H^·). In conjunction with this, ab inito direct dynamics calculations have been conducted, tracing out several hundred reaction trajectories to reveal details of the electron-capture dissociation mechanism. The model calculations suggest the possibility of a bimodal pattern where some of the radicals, formed upon recombination, dissociate almost directly within one picosecond, the remaining radicals being subject to complete energy redistribution with a subsequent dissociation occurring at the microsecond timescale. Both processes give rise to c and z backbone fragments, resulting from cleavage of N–Cα bonds of the peptide chain.

Keywords: Electron capture dissociation, mass spectrometry, proteomics, reaction dynamics, reaction mechanisms

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