Abstract
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 language | English (US) |
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Pages (from-to) | 691-697 |
Number of pages | 7 |
Journal | Biochemistry |
Volume | 35 |
Issue number | 3 |
DOIs | |
State | Published - Jan 23 1996 |
Externally published | Yes |
ASJC Scopus subject areas
- Biochemistry