Synthesis and properties of artificial nucleic acids utilizing pentaerythritol.

First，the synthesis and thermal stabilities of the triplexes containing either2‘-deoxyinosine(1)or2’-deoxyxanthosine(3)in their second strands were examined.It was found that the triplexes with the 2‘-deoxy-5-methylcytidine(DM)·1：dC and dM·1：dA base triplets are thermally stable，but those containing the dM·1：T and dM·1：dG base triplets are unstable under both neutral and slightly acidic conditions.On the other hand，it was found that the oligonucleotide containing3 could form thermally stable triplexes with the oligonucleotides that involve four natural bases opposite the sites of3.The rank of the thermal stabilities of the triplexes was as follows：the triplex containing the dM·3：dC base triplet&gt；that containing the dM3；that containing the dM3：base triplet&gt；that containing the dM3；the dM.Binding ability of a triplex-binding protein(MBP-LOR3^&lt；ARF&gt；)to the triplexes was evaluated by an electrophoretic mobility shift assay(EMSA)。It was found that the triplex，which has an antraquinonecarbonyl group at the 5‘-end of the third strand and is connected with the pentaerythritol linker，has greater affinity to the protein than an unmodified triplex.

First, the synthesis and thermal stabilities of the triplexes containing either 2'-deoxyinosine (1) or 2'-deoxyxanthosine (3) in their second strands were examined. It was found that the triplexes with the 2'-deoxy-5-methylcytidine(dM)・1:dC and dM・1:dA base triplets are thermally stable, but those containing the dM・1:T and dM・1:dG base triplets are unstable under both neutral and slightly acidic conditions. On the other hand, it was found that the oligonucleotide containing 3 could form thermally stable triplexes with the oligonucleotides that involve four natural bases opposite the sites of 3. The rank of the thermal stabilities of the triplexes was as follows : the triplex containing the dM・3:dC base triplet > that containing the dM・3:dA base triplet > that containing the dM・3:T base triplet > that containing the dM・3:dG base triplet.Furthermore, the synthesis of triplexes possessing an anthraquinonyl group and composed of branched oligonucleotides (ONs) was examined. Binding ability of a triplex-binding protein (MBP-LOR3^<ARF>) to the triplexes was evaluated by an electrophoretic mobility shift assay (EMSA). It was found that the triplex, which has an antraquinonecarbonyl group at the 5'-end of the third strand and is connected with the pentaerythritol linker, has greater affinity to the protein than an unmodified triplex.