Photoregulation of DNA hybridization by introducing an azobenzene: molecular design for more stabilization of DNA duplex with cis-azobenzene than with its trans-form.

Previously, photoregulation of DNA hybridization was achieved by introducing nonsubstituted azobenzene via a D-threoninol linker: DNA duplex formed (ON) after visible light irradiation (planar trans-form), whereas the duplex dissociated (OFF) after UV light irradiation (non-planar cis-form). In this study, for more efficient photoregulation of DNA functions, the reverse switch that can turn on duplex formation with UV, and turn off it with visible light irradiation was designed. When para-isopropylazobenzene (p-(i)PrAzo) was introduced into DNA via a L-thereoninol linker, the photoswitching direction was completely reversed: the duplex involving non-planar cis-p-(i)PrAzo was much more stable than that involving planar trans-form.