Evidence for Sequence Scrambling and Divergent H/D Exchange Reactions of Doubly-Charged Isobaric b-Type Fragment Ions
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To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10 2+ that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10 2+ and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10 2+, suggesting that b10 2+ may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10 2+; over 30 % of the observed SORI-CID fragment ions from substance P b10 2+ had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10 2+, whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10 2+.
Key wordsb-Fragment FT-ICR Gas-phase H/D exchange (HDX) Kinetics Sequence scrambling Post-IM/CID SORI-CID
The authors gratefully acknowledge the financial support from the Institute for Therapeutic Discovery (Delanson, NY, USA) and Baylor University.
- 22.Fattahi, A., Solouki, T.: Conformational analysis of metal complexed model peptides and their fragment ions using FT-ICR MS and gas-phase H/D exchange reactions. Proceedings of the 49th ASMS Conference on Mass Spectrometry and Allied Topics. Chicago, IL (May 2001)Google Scholar
- 34.Solouki, T., Zekavat, B., Miladi, M.: On the existence of structurally different isobaric bn fragment ions. Proceedings of the 58th ASMS Conference on Mass Spectrometry and Allied Topics. Salt Lake City, UT (May 2010)Google Scholar
- 38.Gauthier, J.W., Trautman, T.R., Jacobson, D.B.: Sustained off-resonance irradiation for collision-activated dissociation involving Fourier transform mass spectrometry. Collision-activated dissociation technique that emulates infrared multiphoton dissociation. Anal. Chim. Acta. 246, 211–225 (1991)CrossRefGoogle Scholar
- 41.Gucinski, A.C., Somogyi, A., Chamot-Rooke, J., Wysocki, V.H.: Separation and identification of structural isomers by quadrupole collision-induced dissociation-hydrogen/deuterium exchange-infrared multiphoton dissociation (QCID-HDX-IRMPD). J. Am. Soc. Mass Spectrom. 21, 1329–1338 (2010)CrossRefGoogle Scholar
- 44.Miller, T.M.: Atomic and molecular polarizabilities. In: Lide, D.R., Frederikse, H.P.R. (eds.) CRC Handbook of Chemistry and Physics, 77 ed. pp. 193–202, vol. 10. CRC Press Inc., Baton Rouge, (1996/1997)Google Scholar
- 49.Campbell, S., Rodgers, M.T., Marzluff, E.M., Beauchamp, J.L.: Deuterium exchange reactions as a probe of biomolecule structure. Fundamental studies of gas phase wd exchange reactions of protonated glycine oligomers with D2O, CD3OD, CD3CO2D, and ND3. J. Am. Chem. Soc. 117, 12840–12854 (1995)Google Scholar