Oxanine (Oxa), generated as one of the major products from guanine by nitrosative oxidation, has been focused as a mutagenic lesion. Here, Oxa was explored in terms of its unique property to react with - NH2 or -SH group since Oxa possesses O-acylisourea conformation in the base-ring structure. In particular, Oxa has been characterized in terms of its formation and mechanism of DNA-protein cross-link (DPC). In addition, Oxa was testified as a new carboxy-linker for activation-free covalent bonding with NH2-molecules, which can be usefully employed for the design of biotechnological or nano/biotechnological systems.