Projects

Turn residues as well as side-chain interactions play an important role for the folding of ß-sheets. We investigated the conformational dynamics of a three-stranded ß-sheet peptide (^DP^DP) and a two-stranded ß-hairpin (WVYY-^DP) by time-resolved temperature-jump infrared spectroscopy. Both peptide sequences contain ^DPro-Gly residues that favor a tight ß-turn. The three-stranded ß-sheet (Ac-VFITS^DPGKTYTEV^DPGOKILQ-NH₂) is stabilized by the turn sequences, whereas the ß-hairpin (SWTVE^DPGKYTYK-NH₂) folding is assisted both by the turn sequence and by hydrophobic cross-strand interactions. Relaxation times after the T-jump were monitored as a function of temperature and occur on a sub-microsecond time scale, ^DP^DP being faster than WVYY-^DP. The Xxx-^DPro tertiary amide provides a detectable IR band allowing us to site-specifically probe the dynamics. The relative importance of the turn versus the intra-strand stability in ß-sheet formation is discussed.