Fig. 3. TEM images of peptide(GPO)₇DD maintained at 4 °C (a) or incubated at 4 °C for 60 h after preheating at 20 °C for 30 min (b and c). Peptide solutions of (GPO)₇DD with a concentration of 0.5 mg ml⁻¹ were prepared in 100 mM HEPES buffer, pH 7.0.