Sequences and calculated monoisotopic masses for the DNA 60 mer and let7 precursors, definition of predefined symbols for encoding nucleic acid sequences in Nucleo-SAFARI, a module diagram for Nucleo-SAFARI, visualizations of identified fragment ions from UVPD of a m5C66 let7 precursor, annotated spectra of the unmodified and m6A56 let7 precursors, and a comparison of the let7 precursor isotopic distributions can be found in the Supporting Information. All data utilized herein including rawfiles, theoretical fragments, and identified fragments can be found at: