Fast events in protein folding: Helix melting and formation in a small peptide

Skip Williams, Timothy P. Causgrove, Rudolf Gilmanshin, Karen S. Fang, Robert H. Callender, William H. Woodruff, R. Brian Dyer

Research output: Contribution to journalArticlepeer-review

593 Scopus citations


The helix is a common secondary structural motif found in proteins, and the mechanism of helix-coil interconversion is key to understanding the protein-folding problem. We report the observation of the fast kinetics (nanosecond to millisecond) of helix melting in a small 21-residue alanine- based peptide. The unfolding reaction is initiated using a laser-induced temperature jump and probed using time-resolved infrared spectroscopy. The model peptide exhibits fast unfolding kinetics with a time constant of 160 ± 60 ns at 28 °C in response to a laser-induced temperature jump of 18 °C which is completed within 20 ns. Using the unfolding time and the measured helix-coil equilibrium constant of the model peptide, a folding rate constant of approximately 6 x 10 7 s -1 (t( 1/2 ) = 16 ns) can be inferred for the helix formation reaction at 28 °C. These results demonstrate that secondary structure formation is fast enough to be a key event at early times in the protein-folding process and that helices are capable of forming before long range tertiary contacts are made.

Original languageEnglish (US)
Pages (from-to)691-697
Number of pages7
Issue number3
StatePublished - Jan 23 1996
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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