[Synthesis of modified oligonucleotides and use of a duplex from them with covalently bound chains]

A method for the synthesis of DNA duplex with covalently linked strands was elaborated, and the thermal and hydrolytic stability of the duplex was studied. The strands were connected via an amide bond between carboxyl and aliphatic amino groups in the presence of water-soluble carbodiimide. For this purpose, a series of modified 5- to 26-mer oligonucleotides with primary amino or carboxyl group were prepared, and their properties were investigated.