Synthetic oligodeoxyribonucleotides (ODN) have been proposed as a class of potential therapeutic agents that can interact in a rational way with DNA or RNA, with the aim of inhibiting the expression of unwanted genetic information (1 –3 ). One of the most critical questions in the evaluation of these molecules, is their stability toward enzymatic breakdown by [3′ or 5′]-exonucleases and endonucleases (4 ). In order to inhibit or at least limit the effect of these nucleases, chemically modified ODNs have been synthesized.
