G C-MODIFIED OLIGODEOXYNUCLEOTIDES WITH SELECTIVE COMPLEMENTARITY - SYNTHESIS AND HYBRIDIZATION PROPERTIES/

Modified oligodeoxyribonucleotides (ODNs) that have unique hybridizati on properties were designed and synthesized for the first time, These ODNs, called selective binding complementary ODNs (SEC ODNs), are unab le to form stable hybrids with each other, yet are able to form stable , sequence specific hybrids with complementary unmodified strands of n ucleic acid, To make SEC ODNs, deoxyguanosine (dG) and deoxycytidine ( dC) were substituted with deoxyinosine (dl) and ibofuranosyl)pyrrolo-[ 2,3-d]-pyrimidine-2-(3H)-one (dP), respectively, The hybridization pro perties of several otherwise identical complementary ODNs containing o ne or both of these nucleoside analogs were studied by both UV monitor ed thermal denaturation and non-denaturing PAGE, The data showed that while dl and dP did form base pairs with dC and dG, respectively, dl d id not form a stable base pair with dP A self-complementary ODN unifor mly substituted with dl and dP acquired single-stranded character and was able to strand invade the end of a duplex DNA better than an unsub stituted ODN, This observation implies that SEC ODNs should effectivel y hybridize to hairpins present in single-stranded DNA or RNA.