+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

The early life of a peptide cation-radical. Ground and excited-state trajectories of electron-based peptide dissociations during the first 330 femtoseconds



The early life of a peptide cation-radical. Ground and excited-state trajectories of electron-based peptide dissociations during the first 330 femtoseconds



Journal of the American Society for Mass Spectrometry 23(3): 446-459



We report a new approach to investigating the mechanisms of fast peptide cation-radical dissociations based on an analysis of time-resolved reaction progress by Ehrenfest dynamics, as applied to an Ala-Arg cation-radical model system. Calculations of stationary points on the ground electronic state that were carried out with effective CCSD(T)/6-311++G(3df,2p) could not explain the experimental branching ratios for loss of a hydrogen atom, ammonia, and N-C(α) bond dissociation in (AR + 2H)(+•). The Ehrenfest dynamics results indicate that the ground and low-lying excited electronic states of (AR + 2H)(+•) follow different reaction courses in the first 330 femtoseconds after electron attachment. The ground (X) state undergoes competing loss of N-terminal ammonia and isomerization to an aminoketyl radical intermediate that depend on the vibrational energy of the charge-reduced ion. The A and B excited states involve electron capture in the Arg guanidine and carboxyl groups and are non-reactive on the short time scale. The C state is dissociative and progresses to a fast loss of an H atom from the Arg guanidine group. Analogous results were obtained by using the B3LYP and CAM-B3LYP density functionals for the excited state dynamics and including the universal M06-2X functional for ground electronic state calculations. The results of this Ehrenfest dynamics study indicate that reaction pathway branching into the various dissociation channels occurs in the early stages of electron attachment and is primarily determined by the electronic states being accessed. This represents a new paradigm for the discussion of peptide dissociations in electron based methods of mass spectrometry.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 056293633

Download citation: RISBibTeXText

PMID: 22187160

DOI: 10.1007/s13361-011-0283-9


Related references

Ground and Excited-Electronic-State Dissociations of Hydrogen-Rich and Hydrogen-Deficient Tyrosine Peptide Cation Radicals. Journal of the American Society for Mass Spectrometry 27(9): 1454-1467, 2016

Comprehensive analysis of Gly-Leu-Gly-Gly-Lys peptide dication structures and cation-radical dissociations following electron transfer: from electron attachment to backbone cleavage, ion-molecule complexes, and fragment separation. Journal of Physical Chemistry. A 118(1): 308-324, 2014

Perturbing peptide cation-radical electronic states by thioxoamide groups: formation, dissociations, and energetics of thioxopeptide cation-radicals. Journal of Physical Chemistry. A 117(6): 1265-1275, 2013

One-step peptide backbone dissociations in negative-ion free radical initiated peptide sequencing mass spectrometry. Analytical Chemistry 85(15): 7044-7051, 2014

Peptide cation-radicals. A computational study of the competition between peptide N-Calpha bond cleavage and loss of the side chain in the [GlyPhe-NH2 + 2H]+. cation-radical. Journal of Mass Spectrometry 38(10): 1093-1104, 2003

The histidine effect. Electron transfer and capture cause different dissociations and rearrangements of histidine peptide cation-radicals. Journal of the American Chemical Society 132(31): 10728-10740, 2010

Dual electron transfer pathways from 4,4'-dimethoxybenzophenone ketyl radical in the excited state to parent molecule in the ground state. Journal of Physical Chemistry. A 109(31): 6830-6835, 2006

One-electron oxidation of alcohols by the 1,3,5-trimethoxybenzene radical cation in the excited state during two-color two-laser flash photolysis. Journal of Physical Chemistry. A 111(10): 1788-1791, 2007

Ultrafast excited state dynamics of the perylene radical cation generated upon bimolecular photoinduced electron transfer reaction. Journal of Physical Chemistry. A 110(24): 7547-7553, 2006

TEMPO-Assisted Free Radical-Initiated Peptide Sequencing Mass Spectrometry (FRIPS MS) in Q-TOF and Orbitrap Mass Spectrometers: Single-Step Peptide Backbone Dissociations in Positive Ion Mode. Journal of the American Society for Mass Spectrometry (): -, 2016

Sulfur radical cation-peptide bond complex in the one-electron oxidation of S-methylglutathione. Journal of the American Chemical Society 129(29): 9236-9245, 2007

Calculations of the relative energies of the 2B1g and 2A2u states of cyclobutanetetraone radical cation and radical anion provide further evidence of a 3B2u ground state for the neutral molecule: a proposed experimental test of the prediction of a triplet ground state for (CO)4. Journal of Physical Chemistry. A 114(3): 1304-1308, 2009

Electronic excited-state energies from a linear response theory based on the ground-state two-electron reduced density matrix. Journal of Chemical Physics 128(11): 114109-114109, 2008

Uvrr spectroscopy of the peptide bond 2. carbonyl h bond effects on the ground state and excited state structures of n methylacetamide. Journal of the American Chemical Society 113(17): 6368-6377, 1991

Transition metals as electron traps. I. Structures, energetics, electron capture, and electron-transfer-induced dissociations of ternary copper-peptide complexes in the gas phase. Journal of Mass Spectrometry 44(5): 707-724, 2009