TFE titration curve of peptides corresponding to different Im7 helices. Helix I (a), helix II (b), helix III (c) and helix IV (d). The positions of native helices are shown in blue, red, green and yellow, respectively, in each plot. Data were acquired at 10 °C in 50 mM sodium phosphate buffer (pH 7.0). In each case, the spectrum in the absence of TFE is coloured, the spectra in 40% (vol/vol) TFE are shown as dotted lines and the spectra at intermediate concentrations of TFE are shown in continuous black lines. The spectra of helix III in Im7H3M3 are shown in 0% (vol/vol) TFE (purple) and 40% (vol/vol) TFE (black) (e).