Amyloid-Like Structures Formed by Azobenzene Peptides: Light-Triggered Disassembly

The light-driven disassembly process of amyloid-like structures
formed by azobenzene model peptides is studied by time-resolved
mid-IR spectroscopy from nanoseconds to minutes. The investigated
peptide consists of two amino acid strands connected by the
azobenzene switch. The peptides aggregate to amyloid-like
structures when the azobenzene chromophore is in the
trans-conformation. Illumination, resulting in a trans-to
cis-isomerization of the azobenzene, leads to disaggregation of the
aggregated structures. After optical excitation and isomerization
of the azobenzene, one finds absorption changes which recover to a
large extent on the time scale of few nanoseconds. These early
absorption transients are assigned to the relaxation of vibrational
excess energy (heat) or to structural rearrangements of isomerized
azobenzene and the aggregated surroundings. It is only on the time
scale of minutes that spectral signatures appear which are
characteristic for the disassembly of the aggregated structure.