A method of forming a self-connective structure (a hairpin structure, a
four-stranded structure, etc.) of a single-stranded oligonucleotide chain
by forming a mimetic base pair of a mismatch base pair failing to form
any normal base pair among base pairs of the single-stranded
oligonucleotide chain with the use of a compounds represented by the
following general formula (I): A-L-B (I) wherein A represents a chemical
structural moiety capable of forming a pair with one base of a base pair
failing to form any normal base pair; B represents a chemical structural
moiety capable of forming a pair with the other base of the base pair
failing to form any normal base pair; and L represents a linker structure
by which the chemical structures A and B are linked to each other; and a
method of inhibiting the activity of enzyme according to the previous
method.