Table 1.
Sequences, Folding Transition-State Enthalpy ΔH‡, and Folding Rates of the Different Peptides at Neutral pH
| Sequence | Peptide | pH = 7.0 (Salt Bridges) |
pH = 2.5(No Salt Bridges) |
||
|---|---|---|---|---|---|
| (kJ mol−1) | kU → F,298K (μs−1)a | (kJ mol−1) | kU → F,298K (μs−1)a | ||
| Ac-A(EAAAR)3 A-NH2 | (i + 4)ERb | 19.1 ± 1.9 | 4.45 ± 0.15 | 17.8 ± 1.7 | 3.13 ± 0.15 |
| Ac-A(AEAAR)3 A-NH2 | (i + 3)ERb | 15.6 ± 1.1 | 2.06 ± 0.13 | 20.0 ± 3.6 | 1.62 ± 0.21 |
| Ac-A(RAAAE)3 A-NH2 | (i + 4)REb | 14.3 ± 1.9 | 1.98 ± 0.12 | 16.6 ± 3.4 | 2.55 ± 0.30 |
| Ac-A(ARAAE)3 A-NH2 | (i + 3)REb | 7.7 ± 1.4 c | 0.71 ± 0.22 | 19.1 ± 3.0 | 1.26 ± 0.15 |
| Ac-A(DAAAR)3 A-NH2 | (i + 4)DR | 16.1 ± 2.4 | 3.88 ± 0.32 | 21.2 ± 2.1 c | 2.04 ± 0.70 |
| Ac-A(ADAAR)3 A-NH2 | (i + 3)DR | 11.0 ± 1.8 c | 1.54 ± 0.24 | − | − |
| Ac-A(RAAAD)3 A-NH2 | (i + 4)RD | 5.3 ± 1.7 c | 1.00 ± 0.15 | − | − |
| Ac-A(ARAAD)3 A-NH2 | (i + 3)RD | − | − | − | − |
| Ac-A(EAAAK)3 A-NH2 | (i + 4)EK | 21.2 ± 0.9 | 2.19 ± 0.09 | 11.4 ± 4.1 | 1.65 ± 0.21 |
| Ac-A(AEAAK)3 A-NH2 | (i + 3)EK | 18.6 ± 1.4 | 1.40 ± 0.07 | 7.1 ± 4.6 | 1.65 ± 0.40 |
| Ac-A(KAAAE)3 A-NH2 | (i + 4)KE | 19.3 ± 2.4 | 1.22 ± 0.08 | 9.7 ± 3.7 | 1.60 ± 0.15 |
| Ac-A(AKAAE)3 A-NH2 | (i + 3)KE | 11.8 ± 4.2 | 0.87 ± 0.16 | 9.4 ± 4.4 | 1.72 ± 0.21 |
Sequences, folding transition-state enthalpy , and folding rates at 298 K (as determined by interpolating the Arrhenius fit to the data) of the different peptides at neutral pH (salt-bridge formation) and at acidic pH (no salt-bridge effects). Ac, acetyl; A, alanine; E, glutamic acid; R, arginine; D, aspartic acid; K, lysine.
The different peptides were not studied at exactly the same temperatures. For better comparison of the rates, we give the interpolated value at 298 K as obtained from the Arrhenius fit. The uncertainty given is the average of those of the two experimentally determined rates at temperatures closest to 298 K.
Data from (22).
Asymptotic standard errors (80). The error bars on the points of this particular data set were unrealistically large. To obtain realistic estimates for the uncertainties in the parameter values of ΔH‡ and ΔS‡ obtained from the fit to these points, we use the deviation of the data points from the fit to estimate the uncertainties in the parameter values (the so-called asymptotic standard errors, see http://arxiv.org/abs/1210.3781).