Abstract: Aim To synthesize isonucleoside-incorporated ol igonucleotides and investigate their binding abilities with complementary sequen ces. Methods The synthesis was performed on DNA synthesizer, and the binding behavior was investigated by thermal denaturation studies. Results Four kinds of single isonucleoside containing oligonucleoti des were synthesized. The results of thermal denaturation showed that the existe nce of isonucleoside decreased the stability of duplex, and the effect was more obvious when the isonucleoside was in the middle of the sequence. No obvious dif ference was observed when 6'-OH of isonucleoside was free or was protected by allyl group. Conclusions The existence of isonucleoside in oli gonucleotide makes chain twist and decreased the stability of duplex.

Key words: isonucleoside, isonucleoside, nucleotides, nucleotides, hybridization, hybridization, ther mal denaturation, ther mal denaturation