Table II.
Volumetric parameters of apoA-I in solution obtained by PPC: Comparison with globular proteins. The accuracy in determining volume expansion coefficient αv(T) at 5 °C and at 40 °C, α5 and α40, and their difference, α5-40=α40-α5, is 10-15% and is determined by the reproducibility of the PPC data. Uncertainty in the determination of the pre- and post-transitional baselines in the PPC data limits the accuracy in determination of the relative volume change upon unfolding, ΔVunf =(VU-VF)/V, to about 30%; for the same reason, the change in expansivity, Δα unf =α U-α F, may range from about 0.0 to -2.0 × 10-4 depending on the data set and the baseline choice.
| Protein | pH | α5 K-1 |
α5-40 K-1 |
α40 K-1 |
Δα unf K-1 |
ΔVunf % |
|---|---|---|---|---|---|---|
| Chymotrypsina | 2.4 | 6.3 · 10-4 | -0.9 · 10-4 | 5.4 · 10-4 | 1.1 × 10-4 | 0.23 |
| Pespsinogena | 6.4 | 6.8 · 10-4 | -1.2 · 10-4 | 5.6 · 10-4 | 1.0 × 10-4 | 0.00 |
| HEW Lysozymea | 2.5 | 7.1 · 10-4 | -1.7 · 10-4 | 5.4 · 10-4 | 1.4 × 10-4 | -0.08 |
| Trypsin inhibitora | 4.0 | 7.2 · 10-4 | -1.9 · 10-4 | 5.3 · 10-4 | 0.5 × 10-4 | -0.06 |
| Ribonuclease Aa | 5.5 | 8.2 · 10-4 | -2.2 · 10-4 | 6.0 · 10-4 | 1.5 × 10-4 | -0.29 |
| T4 Lysozymea | 3.6 | 9.4 · 10-4 | -2.6 · 10-4 | 6.8 · 10-4 | 0.5 × 10-4 | -0.23 |
| SNaseb | - | 10.0 · 10-4 | -3.5 · 10-4 | 6.5 · 10-4 | 1.2 × 10-4 | -0.15 |
| ApoA-Ic | 7.7 | 15.0 · 10-4 | -4.0 · 10-4 | 11.0 · 10-4 | -1.0 × 10-4 | -0.33 |