title: Light-triggered beta-hairpin folding and unfolding.
abstract: A light-switchable peptide is transformed with ultrashort pulses from a beta-hairpin to an unfolded hydrophobic cluster and vice versa. The structural changes are monitored by mid-IR probing. Instantaneous normal mode analysis with a Hamiltonian combining density functional theory with molecular mechanics is used to interpret the absorption transients. Illumination of the beta-hairpin state triggers an unfolding reaction that visits several intermediates and reaches the unfolded state within a few nanoseconds. In this unfolding reaction to the equilibrium hydrophobic cluster conformation, the system does not meet significant barriers on the free-energy surface. The reverse folding process takes much longer because it occurs on the time scale of 30 micros. The folded state has a defined structure, and its formation requires an extended search for the correct hydrogen-bond pattern of the beta-strand.
authors: Munich Center for Integrated Protein Science, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, 80538 Munich, Germany.
authors: Tobias E
authors: TE
authors: Schrader
authors: Wolfgang J
authors: WJ
authors: Schreier
authors: Thorben
authors: T
authors: Cordes
authors: Florian O
authors: FO
authors: Koller
authors: Galina
authors: G
authors: Babitzki
authors: Robert
authors: R
authors: Denschlag
authors: Christian
authors: C
authors: Renner
authors: Markus
authors: M
authors: Löweneck
authors: Shou-Liang
authors: SL
authors: Dong
authors: Luis
authors: L
authors: Moroder
authors: Paul
authors: P
authors: Tavan
authors: Wolfgang
authors: W
authors: Zinth
mesh_terms: D000577:Amides / Q000737:chemistry; D002244:Carbon; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010100:Oxygen; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared
chemical_list: D000577:Amides; D010455:Peptides; D002244:Carbon; D010100:Oxygen