Table 1. NMR-Derived Data from Peptides with Proline and 4R-Substituted Prolinesa.
| Ac-TYXN-NH2, X = | Ktrans/cis | ΔG (kcal mol–1) | ΔΔG (kcal mol–1) | ref |
|---|---|---|---|---|
| Hyp(4-NO2-Bz) | 8.2 | –1.25 | –0.66 | (10, 11) |
| Flp | 7.0 | –1.15 | –0.56 | (9, 11) |
| Hyp | 5.6 | –1.02 | –0.43 | (9, 11) |
| Pro | 2.7 | –0.59 | 0.00 | (9, 11) |
a
ΔGtrans/cis = −RT ln Ktrans/cis. ΔΔGtrans/cis = ΔGtrans/cis (peptide with proline derivative) – ΔGtrans/cis (peptide with proline), which indicates the magnitude of the structural effect. Experiments were conducted in 90% H2O/10% D2O with 5 mM phosphate buffer pH 4 and 25 mM NaCl. Hyp(4-NO2-Bz): the 4-nitrobenzoate ester of (2S,4R)-4-hydroxyproline; Flp: (2S,4R)-4-fluoroproline; Hyp: (2S,4R)-4-hydroxyproline; Pro: 2S-proline.