Deconvoluted mass spectrums of capping analysis. An enzymatically capped Cap-1 CLuc (A) or FLuc transcript (B) was processed with RNase H and the single-step affinity enrichment and analyzed by LC-MS as described in the main text. The RNase H cleavage products with relevant 5′ groups were identified by their distinct deconvoluted mass values. The area under the identified mass peaks was used to calculate the relative percentage of each species in the sample. A mass corresponded to 24 nt + pG in the Cap-1 form was detected in the FLuc transcript. The addition of a pG was probably the result of T7 polymerase slippage at the 5′ end of the transcript, which is composed of three consecutive guanosine residues.
