The Effect of the Secondary Structure on Dissociation of Peptide Radical Cations: Fragmentation of Angiotensin III and Its Analogues
Fragmentation of protonated RVYIHPF and RVYIHPF-OMe and the corresponding radical cations was studied using time- and collision energy-resolved surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially equipped to perform SID experiments. Peptide radical cations were produced by gas-phase fragmentation of CoIII(salen)-peptide complexes. Both the energetics and mechanisms of dissociation of even-electron and odd-electron angiotensin III ions are quite different. Protonated molecules are much more stable towards fragmentation than the corresponding radical cations. RRKM modeling of the experimental data suggests that this stability is largely attributed to differences in threshold energies for dissociation while activation entropies are very similar. Detailed analysis of the experimental data obtained for radical cations demonstrated the presence of two distinct structures separated by a high free-energy barrier. The two families of structures were ascribed to the canonical and zwitterionic forms of the radical cations produced in our experiments.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 939026
- Report Number(s):
- PNNL-SA-60126; 24493; 24494; KC0302020; TRN: US200820%%451
- Journal Information:
- Journal of Physical Chemistry B, 112(39):12468-12478, Vol. 112, Issue 39
- Country of Publication:
- United States
- Language:
- English
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