Photomodulation of the Conformation of Cyclic Peptides with Azobenzene Moieties in the Peptide Backbone

The cis⇌trans photoisomerization of the azobenzene building block 4-(4-aminophenylazo)benzoic acid incorporated in a cyclic peptide (see scheme) facilitated a two-state transition of the peptide chain from a rigid constrained conformation in the trans isomer into the largely free conformational space of the cis isomer.