Photoswitchable, DNA-binding helical peptides assembled with two independently designed sequences for photoregulation and DNA recognition.

Diarylethene-bridged peptides were developed to photoregulate biomolecular interactions. The peptides are made up of diarylethene-bridged and DNA-binding regions at their N- and C termini, respectively. The two regions could be independently designed and combined as desired. The α-helicities of the peptides were photoregulated in on/off or off/on manners, and the manner depended on the positions of two ornithine (Orn) residues for cross-linking reaction at the diarylethene-bridged region. In the case of the on/off manner, when the diarylethene structure adopted the open form on the peptides, the peptides folded into stable α-helices. Upon UV irradiation, the diarylethene moiety isomerized to its closed form to destabilize the helical structures. Quartz crystal microbalance (QCM) analysis showed that the open isomer strongly associated with a target DNA, as compared with the closed one. When the closed-form peptide existing in the DNA complex was irradiated with a fluorescent lamp in the middle of the QCM monitoring, the frequency change (ΔF) was enhanced by the diarylethene photoisomerization.