%0 Journal Article
%@ 1520-6106
%A Lu, M
%A Ahmed, Z
%A Mikhonin, AV
%A Asher, SA
%D 2007
%F pittir:17221
%J Journal of Physical Chemistry B
%N 26
%P 7675 - 7680
%T UV resonance raman measurements of poly-L-lysine's conformational energy landscapes: Dependence on perchlorate concentration and temperature
%U http://d-scholarship-dev.library.pitt.edu/17221/
%V 111
%X UV resonance Raman spectroscopy has been used to determine the conformational energy landscape of polyL-lysine (PLL) in the presence of NaClO4 as a function of temperature. At 1 °C, in the presence of 0.83 M NaClO4, PLL shows an ∼86% α-helix-like content, which contains ́-helix and π-bulge/helix conformations. The high a-helix-like content of PLL occurs because of charge screening due to strong ion-pair formation between ClO4- and the lysine side chain -NH3+. As the temperature increases from 1 to 60 °C, the ́-helix and π-bulge/helix conformations melt into extended conformations (PPII and 2.51-helix). We calculate the Ψ Ramachandran angle distribution of the PLL peptide bonds from the UV Raman spectra which allows us to calculate the PLL (un)folding energy landscapes along the Ψ reaction coordinate. We observe a basin in the Ψ angle conformational space associated with α-helix and π-bulge/helix conformations and another basin for the extended PPII and 2.5 1-helical conformations. © 2007 American Chemical Society.