Spectral characterization of self-assembled structures formed by synthetic anionic peptides. (A, C, E, and G) CD spectra of anionic peptides in unbuffered water. Peptides were dissolved in unbuffered water (0.3 mM), and spectra were then obtained at acidic pH (pH was 3–4 as a function of residual TFA from HPLC purification); additional spectra were obtained by increasing the pH 7 by addition of NaOH. In the case of peptide E4(FKFE)2, an additional spectrum was obtained at neutral pH in the presence of NaCl, because this was required for formation of β-sheet assemblies. (A) E2(FKFE)2; (C) E4(FKFE)2; (E) E2(ChaKChaE)2; (G) E4(ChaKChaE)2. (B, D, F, and H) FTIR spectra of anionic peptides in unbuffered water. This analysis was performed as described in the legend to Fig. 2. (B) E2(FKFE)2 [NaCl = 0 mM]; (D) E4(FKFE)2 [NaCl = 1 M]; (F) E2(ChaKChaE)2 [NaCl = 0 mM]; (H) E4(ChaKChaE)2 [NaCl = 0 mM].