Characterization of modified oligonucleotides

Oligonucleotides can undergo covalent modifications. [202] These can be natural ones such as those present in tRNA and rRNA but they can also result from reactions with exogenous substances and are the markers indicating possible degradations of the cells. They also can be modified chemically to create new drugs. Almost all these modifications are accompanied by variations in mass, and mass spectrometry is thus useful to identify their nature and position in the sequence. [203-205] 

Collision-induced dissociation FAB/MS/MS trace of As-isopentenyladenosine (25 ng) contained in an unpurified hydrolysate of Ecoli tRNATyr. Reproduced (modified) from Nelson C.C. and McCloskey J.A., Adv. Mass. Spectrom., 11A, 260, 1989, with permission. 

Strategy followed in order to detect and identify the modified constituents of oligonucleotides by HPLC/MS or GC/MS techniques. 

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