meta-Aminoazobenzene as a thermo-insensitive photo-regulator of DNA-duplex formation

meta-Aminoazobenzene has been introduced in the side chain of oligonucleotides as a photo-responsive molecule. Compared with the para-aminoazobenzene which was previously used, the thermal cis→trans isomerization was much slower: the half-lives of the cis-isomers of m- and p-aminoazobenzene were 13.2 h and 20 min at 50°C, respectively. By using the present oligonucleotides, duplex formation and dissociation was efficiently regulated on photo-irradiation without being disturbed by the thermal isomerization.