Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 102, Issue 7, Pages 2379-2384Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0406948102
Keywords
alpha-helix folding; femtosecond IR spectroscopy; protein folding
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Photo-triggered alpha-helix formation of a 16-residue peptide featuring a built-in conformational photoswitch is monitored by time-resolved IR spectroscopy. An experimental approach with 2-ps time resolution and a scanning range up to 30 mus is used to cover all time scales of the peptide dynamics. Experiments are carried out at different temperatures between 281 and 322 K. We observe single-exponential kinetics of the amide I' band at 322 K on a time scale comparable to a recent temperature-jump folding experiment. When lowering the temperature, the kinetics become slower and nonexponential. The transition is strongly activated. Spectrally dispersed IR measurements provide multiple spectroscopic probes simultaneously in one experiment by resolving the amide I' band, isotope-labeled amino acid residues, and side chains. We find differing relaxation dynamics at different spectral positions.
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