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. Author manuscript; available in PMC: 2010 Apr 22.
Published in final edited form as: J Am Chem Soc. 2009 Apr 22;131(15):5444–5459. doi: 10.1021/ja806534r

Figure 3.

Figure 3

IRMPD/ECD of doubly protonated model peptides. a) propanylcysteine, b) benzylcysteine, c) 4-cyanobenzylcysteine, d) perfluorobenzylcysteine, e) 3,5-dicyanobenzylcysteine, f) 3-nitrobenzylcysteine and g) 3,5-dinitrobenzylcysteine containing peptides, respectively. Precursor ions were heated by infrared photons to just below the onset of backbone cleavage. Electron irradiation was applied simultaneously with infrared excitation without isolation of heated precursor ions. Symbolic superscript appendixes °, Δ, ▼ and # indicates loss of hydroxyl radical from [b+1]+• and [y+1]+• ions, and ammonia, water and ethylene from either b and y or w ions, respectively. An asterisk indicates instrumental noise.