Fig. 5. CD spectra data indicates a Fra1–Fra1W interaction. Shown are CD spectra for (a) Fra1 (b) Fra1W and (c) the samples mixed at 1 : 1 stoichiometry. Spectra were measured at 20 °C, 5 °C, and again post thermal denaturation at 20 °C (PM20oC: to establish that unfolding is fully reversible) at a total peptide concentration of 150 μM and presented as mean residue ellipticity (MRE). (d) CD spectra are shown at 20 °C for Fra1 and Fra1W in isolation and when mixed, demonstrating a significant gain in measured signal (black) over the average of the two component signals (red hash). All spectra are indicative of helical structures. All experiments were performed in 10 mM potassium phosphate and 100 mM potassium fluoride (pH 7.0).