Regensburg 2004 – scientific programme
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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology
SYLS 4: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"
SYLS 4.3: Talk
Thursday, March 11, 2004, 10:15–10:30, H 37
Fast Folding Dynamics of α-Helical Peptides — •Martin Volk, Angela Pozo Ramajo, Edmund Leary, and Sarah A. Petty — Department of Chemistry, University of Liverpool, UK
The dynamics of secondary structure formation, which is generally believed to be the first phase of protein folding, has attracted much attention recently, particularly since the application of the temperature jump technique. Using nanosecond lasers, a sudden temperature increase is induced; the ensuing (un)folding can then be observed by suitable time-resolved methods, such as IR-spectroscopy. Previous studies on α-helical model peptides investigated alanine-based peptides containing a repeat motif of the type -(AAAXA)n- (X: hydrophilic amino acid, n = 2-4), which show helix-coil relaxation on the time scale of 150-300 ns.
Here, we report results on longer and more complex helical peptides. We found that the helix-coil relaxation in Poly-N5-(3-hydroxypropyl)-L-glutamine (DP 230) occurs on the same time scale as in alanine-based peptides, in spite of the peptide length and the complex and bulky side chain. On the other hand, the helix-coil relaxation in the random copolymer Poly(Ala, Lys, Glu, Tyr) 6:5:2:1 (DP 180) is much more complex. At high concentrations, it occurs on the µs-time scale and seems to be limited by strong interpeptide interactions of the abundant charged residues, whereas at lower concentrations it shows major deviations from monoexponentiality due to sequence heterogeneity.