Conformations of hydrophobic peptides in trifluoroethanol, water and in solid state: A circular dichroism and Fourier Transform Infrared study

The conformations of peptides corresponding to KLLIALVLCFLPLAALG have been examined in trifluoroethanol (TFE), aqueous medium by circular dichroism sp ectroscopy and in the solid state by Fourier Transform Infra Red Spectrosco py (FTIR). The 17-residue parent peptide and peptides corresponding shorter segments LVLCFLPLAALG and CFLPLAALG showed preference for helical conforma tion in TFE. Even the shorter hydrophobic peptides corresponding to KLLIA a nd LVL showed propensity for beta-turn conformations in TFE. However, pepti des corresponding to the relatively polar segment FLPLAALG were unordered i n TFE. In water, peptides that showed ordered conformation in TFE preferred beta-conformation. In solid-slate, FTIR spectra indicated that the hydroph obic peptides adopt beta-structures with extensive hydrogen bonded network in the solid-state. The hydrophobic core segment thus appears to dictate th e conformational propensity of the peptide.