Preparation of an imidazole-conjugated oligonucleotide.

Postsynthetic modification of an oligonucleotide with an imidazole functional group was achieved by formation of an amide bond between the functional group and a single 2'-amino-2'-deoxyuridine, d-aU, of the oligonucleotide. The succinimidyl ester of N-glutaryl-histamine was synthesized under anhydrous conditions and added to the oligonucleotide in an acetonitrile-containing buffer at pH 8.0. Formation of the conjugate was assayed by digestion with snake venom phosphodiesterase and bacterial alkaline phosphatase, followed by reversed-phase HPLC to resolve constituent nucleosides. The disappearance of a peak corresponding to d-aU and the appearance of a peak that coelutes with authentic 2'-(N-glutaryl-N'-histaminyl)-2'-deoxyuridine confirmed the formation of the conjugate. Imidazole-conjugated oligonucleotides may have utility as antisense agents capable of hydrolyzing RNA.