Impact of ion binding on poly-L-lysine (un)folding energy landscape and kinetics.

ABSTRACT: We utilize T-jump UV resonance Raman spectroscopy (UVRR) to study the impact of ion binding on the equilibrium energy landscape and on (un)folding kinetics of poly-L-lysine (PLL). We observe that the relaxation rates of the folded conformations (including ?-helix (bulge), pure ?-helix, and turns) of PLL are slower than those of short alanine-based peptides. The PLL pure ?-helix folding time is similar to that of short alanine-based peptides. We for the first time have directly observed that turn conformations are ?-helix and ?-helix (bulge) unfolding intermediates. ClO(4)(-) binding to the Lys side chain -NH(3)(+) groups and the peptide backbone slows the ?-helix unfolding rate compared to that in pure water, but little impacts the folding rate, resulting in an increased ?-helix stability. ClO(4)(-) binding significantly increases the PLL unfolding activation barrier but little impacts the folding barrier. Thus, the PLL folding coordinate(s) differs from the unfolding coordinate(s). The-? helix (bulge) unfolding and folding coordinates do not directly go through the ?-helix energy well. Our results clearly demonstrate that PLL (un)folding is not a two-state process.

SUBMITTER: Xiong K 

PROVIDER: S-EPMC3381074 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature