Light-triggered beta-hairpin folding and unfolding.
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.
Schrader
Tobias E
TE
Munich Center for Integrated Protein Science, Ludwig-Maximilians-Universität München, Oettingenstrasse 67, 80538 Munich, Germany.
Schreier
Wolfgang J
WJ
Cordes
Thorben
T
Koller
Florian O
FO
Babitzki
Galina
G
Denschlag
Robert
R
Renner
Christian
C
Löweneck
Markus
M
Dong
Shou-Liang
SL
Moroder
Luis
L
Tavan
Paul
P
Zinth
Wolfgang
W
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
D000577:Amides; D010455:Peptides; D002244:Carbon; D010100:Oxygen