Our series of glutamine-based peptides had overall charges (at pH 7.4) from -6 to +4 (Figure ). Each peptide varies in critical aggregation concentration (c*) as shown by the self-assembly curves derived from 1 H NMR experiments (Figure ). The neutrally charged P11-2 (Q,0) peptide possessed the lowest c* (14 ± 3.2 μM), while the two peptides with the extreme charges, P11-13 (Q,-6) and P11-14 (Q,+4), showed no self-assembly within the concentration range investigated (~1 μM -100 mM). The peptides with +/-2 overall charge, P11-4 (Q,-2) and P11-8 (Q,+2), possessed similar c*: 310 ± 72 and 400 ± 100 μM, respectively . The secondary structures of these peptides under conditions of self-assembly, where applicable, were characterised by FT-IR spectroscopy. Figure shows example spectra for a peptide that does not self-assemble (P11-13 (Q,-6); Figure ) and a peptide that has undergone self-assembly (P11-8 (Q,+2); Figure ). In the case of the extreme charged peptide systems (-6/+4), the peaks in the Amide I region typically associated with β-sheet formation, 1613-1630 cm -1 and 1682-1690 cm -1 , were not present in the FT-IR spectra. Instead, the spectrum is predominantly random coil structure. For peptides that do self-assemble (based on our NMR data), the IR spectra show characteristic peaks for β-sheet content that increase in area as the proportion of β-sheet in the system increases.