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72.5°C for the CeNA-HNA and 67°C for the CeNa-CeNA counterparts. The latter
duplex was studied with oligomers of opposite chirality (the L-series) in view of
insufficient supply of the required T1 monomer. Herewith, however, we uncovered
that the CeNAs of opposite chirality constitute a strong self-pairing system on their
own, resembling L-RNA sequences, but not pairing with natural DNA or RNA.
This is actually the first example of a ‘‘nonnatural-like’’ spiegelmer. The unknown
thymine-thymine interaction as seen before within the HNA series (entry 4, Tm
48.5°C), was noticed here in both CeNA series as well, and is responsible for the
shallow melting curves with inflection point at 37–43°C. Finally, an unexpected
interaction occus between the A2 homopolymer with polyuridine (Tm of 26°C),
which cannot be explained either.
In view of the strong and selective interaction of CeNAs with RNA
complements, and the preservation of RNaseH recognition of a CeNA-RNA
duplex, the CeNAs have a strong potential for antisense strategies.
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