A water-soluble azobenzene cross-linker for photocontrol of peptide conformation.

We have designed and synthesized a water-soluble, sulfonated version of an azobenzene-based thiol-reactive cross-linker that can be introduced into peptides and proteins and act as a conformational photoswitch. The sulfonated compound is shown to effect a similar degree of conformational control on a model peptide helix system, as its nonsulfonated counterpart but can be introduced without the need for any organic cosolvent. The sulfonated azobenzene cross-linker thus expands the range of proteins to which photocontrol can be applied.