Photoswitchable, Water‐Soluble Bisazobenzene Cross‐Linkers with Enhanced Properties for Biological Applications

Photoswitchable cross-linkers are light-responsive molecules that can be attached at two locations to a target biomolecule to modulate its activity. Under irradiation, the cross-linker changes the distance between the residues it spans, affecting the structure and function of the labeled target. Efficient photocontrol is enabled especially by cross-linkers with large end-to-end length change upon switching. The design of water-soluble azobenzene-based cross-linkers for applications in chemical biology remains challenging due to major issues regarding synthesis and purification. Furthermore, the solubility and photochemical properties of the reported systems are frequently not suitable in aqueous media. Herein we report two water-soluble bisazobenzene cross-linkers with extended halflives and high photostationary state isomer distributions that can be achieved upon irradiation. We present molecules that enable cross-linking of biomolecular residues within one target, or are bridging two proteins to allow the study of protein- protein interactions, which paves the way for light-based manipulation of under-explored biological targets.