Figure 2. ECD (a, b), IRMPD (c), and CID (d) MS/MS of bis-nitrated lysozyme. Nitrated tyrosine residues are circled.
respectively, Figure 2. For mononitrated lysozyme, the total
number of fragments was 59, 49, and 25 from ECD, IRMPD, and
CID, respectively, Figures S-3-S-5 in the Supporting Information.
In the summary of MS/MS fragments from mononitrated lysozyme
7288 Analytical Chemistry, Vol. 82, No. 17, September 1, 2010
(Figures S-3-S-5 in the Supporting Information), the nitration site
is assumed to be at Tyr23. However neither ECD, nor IRMPD,
nor CID data exclude the possibility that mono-nitration occurs
at Tyr20. The number of MS/MS fragments containing the site