Models of fragmentations induced by electron attachment to protonated peptides |
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Authors: | Bakken Vebjørn Helgaker Trygve Uggerud Einar |
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Institution: | Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway. |
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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-Calpha bonds of the peptide chain. |
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