activated-ion electron photodetachment dissociation (a-EPD). Fragments were identified directly in the m/z domain by matching against a theoretical list generated from an expected primary structure, a general strategy widely adopted for top-down analysis of proteins. An annotated CID mass spectrum and complete sequence map of the tRNA-Phe gene sequence (m/z 890, 28charge state) is displayed in Figure , and several examples of isotopically resolvable fragment ions are shown as expanded insets. The corresponding 213 nm UVPD and a-EPD spectra are shown in Figures and.