Synthesis of terminally modified oligonucleotides and their hybridization dependence on the size of the target RNAs.

We have developed new artificial oligonucleotide probes that show selective recognition for short RNA targets over long RNA targets. Our results suggested that modification of the termini of the oligonucleotide probes by bulky substituents such as cyclohexyl and 4-(3,6,9-trioxaundecylenedioxy)phenyl (Bzcr) groups significantly improved the selectivity of the probes toward the short RNA targets. The selectivity was further improved by the addition of a phosphate group on the cyclohexane ring.

Synthesis of oligonucleotides terminally modified by bulky and negatively charged substituents and their hybridization with RNA targets.

2'-O-methyl RNAs having phosphorylated cyclohexane groups at the 5' and 3'-terminal bases were synthesized and their hybridization properties toward RNA targets were studied. It was proved that the duplex of the modified 2'-O-methyl RNAs and the target RNA longer than the 2'-O-methyl RNA was less stable than that with the short target. In addition, it was also clarified that the selectivity toward the short target was improved by the introduction of the phosphate group in comparison with that without the phosphate group.

Recognition of target chain-length by use of oligonucleotides having bulky substituents at the terminal bases.

We synthesized 2'-O-methyl RNAs having bulky substituents at the 5' and 3'-terminal bases and examined their hybridization properties. The hybridization of the modified RNAs to the targets RNA was studied varying the chain length of the targets. As the result, it was proved that the duplex of the modified 2'-O-methyl RNAs and the long targets were destabilized in comparison with that of the modified 2'-O-methyl RNAs and the short targets.