Isomerization‐ and Temperature‐Jump‐Induced Dynamics of a Photoswitchable β‐Hairpin

Abstract

Conformational changes in proteins and peptides can be initiated by diverse processes. This raises the question how the variation of initiation mechanisms is connected to differences in folding or unfolding processes. In this work structural dynamics of a photoswitchable β-hairpin model peptide were initiated by two different mechanisms: temperature jump (T-jump) and isomerization of a backbone element. In both experiments the structural changes were followed by time-resolved IR spectroscopy in the nanosecond to microsecond range. When the photoisomerization of the azobenzene backbone switch initiated the folding reaction, pronounced absorption changes related to folding into the hairpin structure were found with a time constant of about 16 μs. In the T-jump experiment kinetics with the same time constant were observed. For both initiation processes the reaction dynamics revealed the same strong dependence of the reaction time on temperature. The highly similar transients in the microsecond range show that the peptide dynamics induced by T-jump and isomerization are both determined by the same mechanism and exclude a downhill-folding process. Furthermore, the combination of the two techniques allows a detailed model for folding and unfolding to be presented: The isomerization-induced folding process ends in a transition-state reaction scheme, in which a high energetic barrier of 48 kJ mol(-1) separates unfolded and folded structures.

Photocontrolled chignolin-derived β-hairpin peptidomimetics

“…MeOH-H 2 O mixtures were spared to avoid the undesired aggregation of the peptidomimetics. This feature, similar to the one observed previously in ATZ, 12,27,28 points to a change of the peptide structure with an open trans-form to a compact cis-form. 3B).…”

Tightening up the structure, lighting up the pathway: application of molecular constraints and light to manipulate protein folding, self-assembly and function

“…In particular, azobenzene and its derivatives [71-77] have become the most popular choice. Similar to stilbene [78-80], azobenzene undergoes ultrafast isomerization at the excited electronic state [81, 82]; it is this process (Figure 5), which can effectively change the distance between the two ends of the azobenzene linker, that is used to modulate protein structures in practice.…”

Light and heat control over secondary structure and amyloid-like fiber formation in an overcrowded-alkene-modified Trp zipper

“…This would permit photo-triggered formation of secondary structure of a β-hairpin peptide. Notably, trpzip peptide was already modified by Moroder 23 with an azobenzene switch at the same position, which allows to compare the effects of the overcrowded alkene and the azobenzene switches.…”