Fragmentation energetics for angiotensin II and its analogs from time-and energy-resolved surface-induced dissociation studies

Surface-induced dissociation (SID) of four model peptides: DRVYIHPF, RVYIHPF, RVYIHAF, and RVYIHDF was studied using a novel Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially configured for SID experiments. The energetics and dynamics of peptide fragmentation were deduced by modeling the time- and energy-resolved survival curves for each precursor ion using an RRKM based approach developed in our laboratory. Accurate dissociation parameters can be obtained from these experiments because collision-energy-resolved SID data are very sensitive to both the energetics and dynamics of dissociation. We found that transition from selective to non-selective fragmentation as ion kinetic energy is increased is associated with a substantial (ca. 0.5 eV) increase in the dissociation energy and a 3-4 orders of magnitude increase in the pre-exponential factor. Dissociation thresholds for angiotensin analogs derived from the experimental data are as follows: 1.62 eV for RVYIHAF and RVYIHPF, 1.14 eV for RVYIHDF and 1.13 eV for DRVYIHPF. Pre-exponential factors of 8.2 x 10(11), 7.2 x 10(12), 3.1 x 10(8), and 5.0 x 10(7) s(-1) were obtained for RVYIHPF, RVYIHAF, RVYIHDF, and DRVYIHPF, respectively. Contribution from shattering to the total decomposition of the precursor ion increases for kinetically hindered fragmentation. The largest contribution is observed for a peptide ion that has the largest negative reaction entropy-DRVYIHPF. (C) 2004 Elsevier B.V. All rights reserved.