. . . "A compound of the formula A3 --(--X--R1 --E--)m where A3 is an oligo- or polynucleotide having at least one modifiable reactive group consisting of amino, hydroxy, cis OH, halide, aryl, imidazoyl, carbonyl, carboxyl, thiol or a residue comprising an activated carbon where the modifiable group is contained within or attached to a sugar or a phosphate moiety; --X-- is selected from the group consist" .