@article{pittir17221,
          volume = {111},
          number = {26},
           month = {July},
          author = {M Lu and Z Ahmed and AV Mikhonin and SA Asher},
           title = {UV resonance raman measurements of poly-L-lysine's conformational energy landscapes: Dependence on perchlorate concentration and temperature},
         journal = {Journal of Physical Chemistry B},
           pages = {7675 -- 7680},
            year = {2007},
             url = {http://d-scholarship-dev.library.pitt.edu/17221/},
        abstract = {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 {$\sim$}86\% {\ensuremath{\alpha}}-helix-like content, which contains ?-helix and {\ensuremath{\pi}}-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 {\ensuremath{\pi}}-bulge/helix conformations melt into extended conformations (PPII and 2.51-helix). We calculate the {\ensuremath{\Psi}} 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 {\ensuremath{\Psi}} reaction coordinate. We observe a basin in the {\ensuremath{\Psi}} angle conformational space associated with {\ensuremath{\alpha}}-helix and {\ensuremath{\pi}}-bulge/helix conformations and another basin for the extended PPII and 2.5 1-helical conformations. {\copyright} 2007 American Chemical Society.}
}