Kinetics for tautomerizations and dissociations of triglycine radical cations.
Fragmentations of tautomers of the alpha-centered radical triglycine radical cation, [GGG(*)](+), [GG(*)G](+), and [G(*)GG](+), are charge-driven, giving b-type ions; these are processes that are facilitated by a mobile proton, as in the fragmentation of protonated triglycine (Rodriquez, C. F. et al. J. Am. Chem. Soc. 2001, 123, 3006-3012). By contrast, radical centers are less mobile. Two mechanisms have been examined theoretically utilizing density functional theory and Rice-Ramsperger-Kassel-Marcus modeling: (1) a direct hydrogen-atom migration between two alpha-carbons, and (2) a two-step proton migration involving canonical [GGG](*+) as an intermediate. Predictions employing the latter mechanism are in good agreement with results of recent CID experiments (Chu, I. K. et al. J. Am. Chem. Soc. 2008, 130, 7862-7872).
Siu
Chi-Kit
CK
Department of Chemistry and Centre for Research in Mass Spectrometry, York University, Toronto, Ontario, Canada.
Zhao
Junfang
J
Laskin
Julia
J
Chu
Ivan K
IK
Hopkinson
Alan C
AC
Siu
K W Michael
KW
D000465:Algorithms; D002412:Cations / Q000737:chemistry; D006859:Hydrogen; D007536:Isomerism; D007700:Kinetics; D013058:Mass Spectrometry; D008956:Models, Chemical; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics
D002412:Cations; D009842:Oligopeptides; D011522:Protons; D006859:Hydrogen; C035647:glycyl-glycyl-glycine