10.1021/jp302007g.s001
Kan Xiong
Kan
Xiong
Sanford A. Asher
Sanford A.
Asher
Impact of Ion Binding
on Poly-l-Lysine (Un)folding
Energy Landscape and Kinetics
American Chemical Society
2012
activation barrier
equilibrium energy landscape
helix
impact
relaxation rates
Ion Binding
peptide backbone
ion binding
UV
UVRR
NH
PLL
2012-06-21 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Impact_of_Ion_Binding_on_Poly_l_Lysine_Un_folding_Energy_Landscape_and_Kinetics/2511772
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 π-helix
(bulge), pure α-helix, and turns) of PLL are slower than those
of short alanine-based peptides. The PLL pure α-helix folding
time is similar to that of short alanine-based peptides. We for the
first time have directly observed that turn conformations are α-helix
and π-helix (bulge) unfolding intermediates. ClO<sub>4</sub><sup>–</sup> binding to the Lys side chain −NH<sub>3</sub><sup>+</sup> groups and the peptide backbone slows the α-helix
unfolding rate compared to that in pure water, but little impacts
the folding rate, resulting in an increased α-helix stability.
ClO<sub>4</sub><sup>–</sup> 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-π helix (bulge) unfolding and folding coordinates
do not directly go through the α-helix energy well. Our results
clearly demonstrate that PLL (un)folding is not a two-state process.