Characterization of oligodeoxyribonucleotide-polyethylene glycol conjugates by electrospray mass spectrometry

Electrospray mass spectrometry (ESMS) was used to characterize a number of differently functionalized polyethylene glycol-oligodeoxyribonucleotide conjugates. Sample preparation was found to be crucial to obtaining quality data. The resolution and precision of ESMS allowed for the identification of individual conjugates differing in MW by a single ethylene glycol unit with an accuracy of < or = 1 (0.02% of the molecular weight). In addition, ESMS was shown to be valuable in identifying chromatographically unresolvable components of a derivatized polyethylene glycol-oligonucleotide conjugate mixture.