a. CD spectra of PE in the presence of TFE (trifluorethanol). CD spectra for PE were obtained under different concentrations of the trifluoroethanol (TFE), an organic solvent. TFE of 0% to 33% was found to alter the CD spectra of PE, indicating alterations in secondary structure.
b. Increase in alpha-helical structure of PE in the presence of TFE. The relative extent (percent) of changes in secondary structural features with increasing concentrations of TFE (0 to 33%) are illustrated for alpha-helix (■), beta-sheet (○), and beta-turn (△) features. TFE substantially increases the alpha-helical secondary structure of PE.