Probing the fastest dynamics in peptide conformational dynamics

In this study, a suitably functionalized azobenzene molecule, (4-aminophenyl)azobenzoic acid, is incorporated as a fast photo-switch into a backbone-cyclized peptide built up from eight amino-acids. Femtosecond transient absorption spectroscopy with 60 fs excitation pulses (480 nm) and white light probing (generated in CaF/sub 2/) record the molecular reaction. Femtosecond experiments have been performed on the cyclic peptide and a linear peptide which serves as a reference system where the conformation is not constrained.