Versatile procedure of multiple introduction of 8-aminomethylene blue into oligonucleotides

The coupling of 8-aminomethylene blue to oligonucleotides via poly-L-glutamic acid linker using carboxy-anchor groups will be described. The introduction of carboxy-anchor groups into oligonucleotides proceeds both during automated synthesis using 6-(ethoxycarbonyl)hexyl 1-O-phosphoramidite and by reaction of 5'-amino-functionalized oligonucleotides with succinic anhydride. O-(N-Succinimidyl)-1,1,3,3-tetramethyluronium tetrafluoroborate was used as activating reagent for binding of poly-L-glutamic acid to the carboxylated oligonucleotides. The successful 5'-carboxylation and poly-L-glutamic acid coupling were proven both by polyacrylamide gel electrophoreses and HPLC. 8-Aminomethylene blue in its leucoform was covalently coupled to the oligonucleotides in the presence of water soluble carbodiimide.