Understanding the folding mechanism of an alpha-helical hairpin

The effects of the turn, the hydrophobic cluster, and a disulfide cross-linker on the folding kinetics of a designed alpha-helical hairpin, Z34C, are examined using an infrared temperature-jump method in conjunction with site-specific mutagenesis. Results reveal that Z34C folds with an ultrafast rate and support a folding mechanism in which the rate-limiting step corresponds to the formation of the reverse turn.