Photo-control of peptide conformation on a timescale of seconds with a conformationally constrained, blue-absorbing, photo-switchable linker

Abstract

Azobenzene derivatives can be used to reversibly photo-regulate conformation and activity when introduced as intramolecular bridges in peptides and proteins. Here we report the design, synthesis, and characterization of an azobenzene derivative that absorbs between 400–450 nm in aqueous solution to produce the cis isomer, and relaxes back to the trans isomer with a half-life of a few seconds at room temperature. In the trans form, the linker can span a distance of approximately 25 Å, so that it can bridge Cys residues spaced i, i + 15 in an α-helix. Switching of the azobenzene cross-linker from trans to cis causes a decrease in the helix content of peptides where the linker is attached via Cys residues spaced at i, i + 15 and i, i + 14 positions, no change in helix content with Cys residues spaced i, i + 11 and an increase in helix content in a peptide with Cys residues spaced at i, i + 7. In the presence of 10 mM reduced glutathione, the azobenzene cross-linker continued to photo-switch after 24 hours. This cross-linker design thus expands the possibilities for fast photo-control of peptide and protein structure in biochemical systems.