4'-THIO-RNA - SYNTHESIS OF MIXED BASE 4'-THIO-OLIGORIBONUCLEOTIDES, NUCLEASE RESISTANCE, AND BASE-PAIRING PROPERTIES WITH COMPLEMENTARY SINGLE AND DOUBLE-STRAND

4'-Thio-beta-D-oligoribonucleotides (12 mer and 16 mer) containing a m ixed base sequence were synthesized via the phosphoramidite solid supp ort approach, These RNA analogs showed very good nuclease resistance a s compared with wild-type RNA, Furthermore, 4'-thio-beta-D-oligoribonu cleotides were shown to hybridize with a complementary DNA or RNA stra nd to form a duplex or with a DNA hairpin to form a triple helix. 4'-T hio-RNA binds more tightly to its complementary RNA strand than to its complementary DNA strand, A 4'-thio-RNA:RNA duplex is as stable as a 2'-O-methyl-RNA:RNA duplex. 4'-Thio-RNA, however, forms a 4'-thio-RNA: DNA:DNA tripler with a stability similar to the corresponding tripler with all wild-type DNA.