TEM investigations further revealed that in absence of Zn(II), a fibrous network of long and flexible fibers is formed (Fig. ). However, the hydrogels containing 0.5 equiv. of Zn(II) tend to form a fibrous network of stacked and more straight nanofibers, whereby higher peptide concentrations result in shorter fibers, as shown in Fig. and, respectively. Mechanical stiffness and viscoelastic character of the peptide hydrogels were evaluated through oscillatory rheology experiments. Hydrogels were prepared at a consistent peptide concentration of 1.9 wt% (19 mg mL -1 ) and pH ~7-7.4. A series of experiments were conducted to quantify the differences in hydrogel behavior between aqueous and 10% phosphate-buffered saline (PBS) solutions with and without Zn(II). The peptide concentration was carefully selected to ensure hydrogel formation in both cases.