Spectroscopic Investigation of H Atom Transfer in a Gas-phase Dissociation Reaction: McLafferty Rearrangement of Model Gas-phase Peptide Ions
Wavelength-selective infrared multiple-photon photodissociation (WS-IRMPD) was used to study isotopically-labeled ions generated by McLafferty rearrangement of nicotinyl-glycine-tert-butyl ester and betaine-glycine-tert-butyl ester. The tert-butyl esters were incubated in a mixture of D2O and CH3OD to induce solution-phase hydrogen-deuterium exchange and then converted to gas-phase ions using electrospray ionization. McLafferty rearrangement was used to generate the free-acid forms of the respective model peptides through transfer of an H atom and elimination of butene. The specific aim was to use vibrational spectra generated by WS-IRMPD technique to determine whether the H atom remains at the acid group, or migrates to one or more of the other exchangeable sites. Comparison of the IRMPD results in the region from 1200-1900 cm-1 to theoretical spectra for different isotopically-labeled isomers clearly shows that the H atom is situated at the C-terminal acid group and migration to amide positions is negligible on the time scale of the experiment. The results of this study suggest that use of the McLafferty rearrangement for peptide esters could be an effective approach for generation of H-atom isotope tracers, in-situ, for subsequent investigation of intra-molecular proton migration during peptide fragmentation studies.
- Research Organization:
- Idaho National Laboratory (INL)
- Sponsoring Organization:
- OTHER
- DOE Contract Number:
- AC07-99ID13727
- OSTI ID:
- 936872
- Report Number(s):
- INL/JOU-08-14032
- Journal Information:
- Physical Chemistry Chemical Physics, Journal Name: Physical Chemistry Chemical Physics Journal Issue: 22 Vol. 10; ISSN 1463-9076
- Country of Publication:
- United States
- Language:
- English
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