MS/MS spectra of ss12+ENU by (a) EPD of 3-• (one UV pulse, 5mJ; then 37% normalized collision energy, 30 ms), and (b) CID 3- (37% normalized collision energy, 30 ms). Precursor ions are noted with a star. Bolded and italicized product ions retain the modification. Not all of the EPD product ions are labeled due to the complexity of the spectrum. A summary of the product ions formed from EPD and CID for the ENU modified single strand 12-mer (c), in which the slash marks represent cleavages at that location. A triangle above the slash mark represents a product containing the ENU modification.