Table 1. Sequence, Apparent Transition Enthalpy (ΔHapp‡), and Entropy (ΔSapp) for the Folding (U → F) Transitions of the Four Investigated Peptides at Neutral pH (Salt Bridge Formation) and at Acidic pH (No Salt Bridge Effects).
| pH = 7.0 (with
salt
bridge) |
pH = 2.5 (no salt
bridge) |
||||
|---|---|---|---|---|---|
| sequencea | peptidea | ΔHapp (U→F)‡ (kJ mol–1) | ΔSapp (U→F)‡ (J mol–1 K–1) | ΔHapp (U→F)‡ (kJ mol–1) | ΔSapp (U→F)‡ (J mol–1 K–1) |
| Ac-A(EAAAR)3A-NH2 | (i + 4)ER | 16.6 ± 1.2 | –62.0 ± 4.0 | 15.3 ± 1.7 | –69.3 ± 5.8 |
| Ac-A(AEAAR)3A-NH2 | (i + 3)ER | 13.1 ± 1.1 | –80.1 ± 3.6 | 17.5 ± 3.6 | –67.3 ± 12.3 |
| Ac-A(RAAAE)3A-NH2 | (i + 4)RE | 11.9 ± 1.9 | –84.7 ± 6.4 | 14.1 ± 3.4 | –75.0 ± 11.8 |
| Ac-A(ARAAE)3A-NH2 | (i + 3)RE | 5.2 ± 1.5b | –115.4 ± 5.1b | 16.7 ± 3.0 | –72.2 ± 10.3 |
a
Ac = acetyl; A = alanine; E = glutamic acid; R = arginine.
b
These are asymptotic standard errors.37