Proton Nuclear Magnetic Resonance Measurements of 2′‐Aminodeoxyuridylyl‐3′,5′‐Deoxyuridine

A dideoxyribonucleotide, 2′‐amino‐2′‐deoxyuridylyl 3′,5′‐deoxyuridine, containing an unsual base (2′‐amino‐2′‐deoxyuridine) that isresistant to nucleases was investigated by ′H NMR. The pK_a of the protonation of the amino group (5.8) was determined by profiles of chemical shifts of protons in the vicinity of amino group versus pH. However, protonation of the amino group has little effect on the conformation of the dimer, assumed to be B‐form DNA. This conclusion is drawn from the chemical shift data and coupling constants of H₁‐H₂. Thus, 2′‐amino‐2′‐deoxyuridine can be used in antisense and anticode oligonucleotides.