Photomodulation of conformational states in cyclic peptides by cis/trans isomerization of azobenzene

For photomodulation of conformational, physicochemical, and biological properties large use is made of the cis/trans isomerization of azobenzene grafted to specific sites of biomaterials and related model systems [1]. To optimally exploit the configurational changes of the azobenzene, the related amino acids (4-amino)phenylazobenzoic acid (HAPB-OH) and (4-aminomethyl)phenylazobenzoic acid (H-AMPB-OH) were synthesized for incorporation into the backbone of cyclic peptides. MD calculations served for the design of optimal ring-sizes to freeze conformationally the peptide backbone in the transisomer state and thus to amplify the effect of local topochemical changes of the lightinduced trans cis azobenzene isomerization on the conformation of the cyclic peptides.