Light-triggered β-hairpin folding and unfolding

Tobias E. Schrader, Wolfgang J. Schreier, Thorben Cordes, Florian O. Koller, Galina Babitzki, Robert Denschlag, Christian Renner, Markus Löweneck, Shou-Liang Dong, Luis Moroder, Paul Tavan, Wolfgang Zinth

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A light-switchable peptide is transformed with ultrashort pulses from a β-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 β-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 µs. The folded state has a defined structure, and its formation requires an extended search for the correct hydrogen-bond pattern of the β-strand.
Original languageEnglish
Pages (from-to)15729-15734
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number40
Publication statusPublished - 2007


  • ultrafast infrared spectroscopy
  • TrpZip2
  • peptide folding
  • density functional theory calculation

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