Oxanine (Oxa, O), one of the major products generated from guanine (Gua) by nitrosative oxidation has been expected as mutagenic lesion involved in NO- or HNO(2) -induced genotoxicity. Here, to elucidate the biological meaning of Oxa in DNA strands, several kinds of Oxa-containing oligodeoxynucleotides (Oxa-ODNs) were synthesized and applied to biophysical and biochemical characterization. CD and NMR analyses revealed that the conformations of all the Oxa-containing duplexes are basically B-type without causing any severe distortion in the whole DNA structure. It was also determined that restriction endonucleases recognize and cleave the specific base-sequence even when Gua was substituted by Oxa in the sequence. When Oxa-ODN was testified as substrates for other DNA-relevant enzymes, the enzymatic functions were not largely affected by Oxa.