Table 4.
Summary of NMR data for β-hairpin model peptides.
| δ, Hα, ppm | 3JαN, Hz | |||||
|---|---|---|---|---|---|---|
| X = N | X = C-SO2− | X = C-SH | X = N | X = C-SO2− | X = C-SH | |
| R | 4.05 | 4.05 | 4.04 | - | - | - |
| Y | 4.99 | 4.90 | 4.83 | 7.6 | 7.3 | 7.2 |
| V | 4.16 | 4.16 | 4.10 | nr | nr | 9.4 |
| E | 4.67 | 4.56 | 4.56 | 7.6 | nr | nr |
| V | 4.23 | 4.16 | 4.16 | 9.2 | nr | nr |
| X | 4.54 | 4.41 | 4.36 | 5.8 | 4.5 | 6.1 |
| G | 4.00, 3.80 | 3.98, 3.86 | 3.94 | 5.8 | 8.5 | nr |
| O | 4.53 | 4.47 | 4.44 | 8.0 | nr | 8.0 |
| K | 4.44 | 4.41 | 4.37 | 7.0 | nr | 7.0 |
| I | 4.37 | 4.30 | 4.25 | 9.0 | nr | nr |
| L | 4.23 | 4.26 | 4.30 | nr | 6.8 | 6.9 |
| Q | 4.29 | 4.28 | 4.28 | 7.6 | nr | nr |
NMR data were acquired at pH 3.9 in 100 mM deuterated sodium acetate in a solution of 10% D2O in H2O at 4 °C. Resonances indicated as “nr” were not sufficiently resolved to determine coupling constants. Notably, Cys-SO2− has a small 3JαN, which indicates a compact conformation in ϕ at this residue. The 3JαN of this residue and the following glycine are consistent with a type II’ β-turn, while those of the asparagine and glycine in peptide β12-N6 are consistent with either a type I’ or type II’ β-turn (this peptide adopts a type I’ β-turn). In the peptide β12-C6-SH, the diastereotopic glycine Hα do not have distinct chemical shifts, indicating less order round that residue.