[Affinity modification of EcoRII restriction endonuclease by a DNA-duplex containing a monosubstituted pyrophosphate internucleotide bond].

Oligonucleotide duplex with an active monosubstituted pyrophosphate bond within the recognition site of the EcoRII restriction endonuclease was cross-linked to this enzyme with a yield of 10-15%. The cross-linking specificity was proved by the absence of the cross-linking to a DNA duplex with the same modification but without the EcoRII recognition site as well as by unmodified EcoRII substrate's inhibition of the cross-linking.