May 31, 2008
Journal Article

Are the Radical Centers in Peptide Radical Cations Mobile? The Generation, Tautomerism, and Dissociation of Isomeric a-Carbon-Centered Triglycine Radical Cations in the Gas Phase

Abstract

The mobility of the radical center in three isomeric triglycine radical cationss[G•GG]+, [GG•G]+, and [GGG•]+shas been investigated theoretically via density functional theory (DFT) and experimentally via tandem mass spectrometry. These radical cations were generated by collision-induced dissociations (CIDs) of Cu(II)-containing ternary complexes that contain the tripeptides YGG, GYG, and GGY, respectively (G and Y are the glycine and tyrosine residues, respectively). Dissociative electron transfer within the complexes led to observation of [Y•GG]+, [GY•G]+, and [GGY•]+; CID resulted in cleavage of the tyrosine side chain as p-quinomethide, yielding [G•GG]+, [GG•G]+, and [GGG•]+, respectively. Interconversions between these isomeric triglycine radical cations have relatively high barriers (g44.7 kcal/mol), in support of the thesis that isomerically pure [G•GG]+, [GG•G]+, and [GGG•]+ can be experimentally produced. This is to be contrasted with barriers

Revised: October 23, 2013 | Published: May 31, 2008

Citation

Chu I.K., J. Zhao, J. Zhao, M. Xu, S. Siu, A.C. Hopkinson, and A.C. Hopkinson, et al. 2008. Are the Radical Centers in Peptide Radical Cations Mobile? The Generation, Tautomerism, and Dissociation of Isomeric a-Carbon-Centered Triglycine Radical Cations in the Gas Phase. Journal of the American Chemical Society 130, no. 25:7862–7872. doi:10.1021/ja801108j