CROSS-LINKED DNA DUPLEXES WITH INTERSTRAND SUBSTITUTED PYROPHOSPHATE GROUP - SYNTHESIS AND PROPERTIES

A novel reaction involving the internucleotide phosphate of double-str anded DNA was proposed to obtain cross-linked DNA duplexes containing a reactive interstrand monosubstituted pyrophosphate group. The reacti on takes place between activated terminal phosphate group linked to an oligonucleotide probe via a spacer unit, and proximal internucleotide phosphate, group of complementary oligonucleotide. Propane-, butane-, heptane-, and dodecandioles as well as 1,2-dideoxy-D-ribofuranose ser ved as spacer units. Activation of the probe terminal phosphate was ca rried out using 1-ethyl-3(3'-dimethylaminopropyl)carbodiimide. The yie ld of the cross-linked duplexes was the highest with probes including propylene- or 1,2-dideoxy-D-ribofuranoside spacer units; it amounted u p to 40%. Some properties of these compounds were investigated. It was found that the trisubstituted pyrophosphate group was selectively cle aved by nucleophilic agents such as N-methylimidazole and ethylendiami ne. This reaction proceeds in aqueous media and results in transfer of one of oligonucleotide residues of the covalently bound duplex to the nucleophilic agent. The nucleophilic substitution proceeds simultaneo usly at both phosphates of the trisubstituted pyrophosphate group.