Characterization of an alkylated dinucleotide by desorption chemical ionization and tandem mass spectrometry

A highly sensitive (subpicomole level), structure-specific method of analysis has been developed for characterizing and quantitating the dinucleotide thymidylyl(3′ 5′)thymidine methyl phosphotriester by desorption chemical ionization tandem mass spectrometry. The methodology can be applied to related compounds such as the parent dinucleotide and employs either positive or negative ionization mass spectra or daughter spectra. The procedure allows specification of the site of methyl attachment.