Fast side-chain losses in keV ion-induced dissociation of protonated peptides |
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Authors: | Sadia Bari Ronnie Hoekstra Thomas Schlathölter |
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Institution: | KVI Atomic and Molecular Physics, University of Groningen, Zernikelaan 25, 9747AA Groningen, The Netherlands |
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Abstract: | In this paper, we compare ionization and dissociation of a series of singly and doubly protonated peptides, namely leucine enkephalin, bradykinin, LHRH and substance P as induced by collisions with keV H+, He+ and He2+. For all peptides under study, the fragmentation pattern depends strongly on the electronic structure of the projectile ions. Immonium ions, side-chains and their fragments dominate the spectrum whereas fragments due to peptide backbone cleavage are weak or even almost absent for He+. Here, resonant electron capture from the peptide is ruled out and only interaction channels accompanied by much higher excitation contribute. Cleavage of the side-chain linkage appears to be a process alternative to backbone fragmentation occurring after internal vibrational redistribution of excitation energy. Depending on the peptide, this process can lead to the loss of a side-chain cation (leucine enkephalin, LHRH) or a neutral side-chain (substance P). |
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