| abstract |
Provided is an oligonucleotide, etc. which has, at the 5' terminal of the oligonucleotide, a nucleotide residue or a nucleoside residue represented by formula (I) {in formula (I), X 1 represents an oxygen atom, etc., R 1 represents formula (IIA) (in formula (IIA), R 5A represents halogen, etc., and R 6A represents a hydrogen atom, etc.), or formula (IVA), etc. (in formula (IVA), Y 3A represents a nitrogen atom, etc., and Y 4A represents CH, etc.), R 2 represents a hydrogen atom, a hydroxy, halogen, or an optionally substituted lower alkoxy, and R 3 represents a hydrogen atom, etc.}, said nucleotide residue or nucleoside residue bonds, via an oxygen atom at position 3, with an adjoining nucleotide residue, and the oligonucleotide has an improved affinity with AGO2. |