MS/MS spectra of Mss10 by (a) EPD of 3-• (one UV pulse, 5mJ; then 8% normalized collision energy, 30 ms), and (b) CID 3- (8% normalized collision energy, 30 ms). Precursor ions are noted with a star. Bolded and italicized product ions retain the modification. A summary of the product ions formed from EPD and CID for the methylated single strand 10-mer (c), in which the slash marks represent cleavages at that location. A crescent above the slash mark represents a product containing the methyl modification. .