Preparation of an imidazole-conjugated oligonucleotide

Postsynthetic modification of an oligonucleotide with an imidazole function al 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 anhydr ous conditions and added to the oligonucleotide in an acetonitrile-containi ng buffer at pH 8.0. Formation of the conjugate was assayed by digestion wi th snake venom phosphodiesterase and bacterial alkaline phosphatase, follow ed by reversed-phase HPLC to resolve constituent nucleosides. The disappear ance of a peak corresponding to d-aU and the appearance of a peak that coel utes with authentic 2'-(N-glutaryl-N'-histaminyl)-2'- deoxyuridine confirme d the formation of the conjugate. Imidazole-conjugated oligonucleotides may have utility as antisense agents capable of hydrolyzing RNA.