title: Folding and unfolding of light-triggered β-hairpin model peptides.
abstract: Ultrafast spectroscopy in the visible and mid-infrared is used to study the reaction dynamics of two light-triggered model peptides containing an azobenzene derivative as a switching element. One model peptide, the AzoTrpZip2, forms a β-hairpin structure in the cis form of the chromophore. This peptide is compared to the core structure consisting of the chromophore and the two flanking amino acid residues, used as a minimal model. This combination of experiments performed in different spectral ranges on peptides of different sizes allows for improved insight into light triggered reaction dynamics. The kinetics observed for the core structure are directly connected to the switching process of the chromophore and are finished on the 10 ps time scale. The trans-to-cis reaction of AzoTrpZip2, leading to the formation of the β-hairpin structure involves ultrafast processes on the 100 ps time scale, which are directly related to the relaxation of the strain between the isomerized molecular switch and the two peptide strands. IR-signatures characteristic for changes in interstrand interactions are absent on the <1 ns time scale. Thus folding into the β-hairpin structure occurs on a much longer time scale. In the cis-to-trans unfolding reaction, all IR signatures related to changes in interstrand interactions occur within 1 ns, in a time range where visible spectroscopy reveals the final decay of the intramolecular strain. Apparently unfolding of AzoTrpZip2 is to a large extent a fast, driven process.
authors.affiliation: Ludwig-Maximilians-Universität München, Lehrstuhl für BioMolekulare Optik and Munich Center for Integrated Protein Science CIPSM, Oettingenstrasse 67, 80538 München, Germany.
authors.forename: Tobias E
authors.initials: TE
authors.lastname: Schrader
authors.forename: Thorben
authors.initials: T
authors.lastname: Cordes
authors.forename: Wolfgang J
authors.initials: WJ
authors.lastname: Schreier
authors.forename: Florian O
authors.initials: FO
authors.lastname: Koller
authors.forename: Shou-Liang
authors.initials: SL
authors.lastname: Dong
authors.forename: Luis
authors.initials: L
authors.lastname: Moroder
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Zinth
mesh_terms: D000595:Amino Acid Sequence; D001391:Azo Compounds / Q000737:chemistry; D055029:Inverted Repeat Sequences; D010455:Peptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D058767:Protein Unfolding; D013055:Spectrophotometry, Infrared
chemical_list: D001391:Azo Compounds; D010455:Peptides; C009850:azobenzene