TABLE 3.
Thermodynamic parameters characterizing the urea-induced unfolding transition monitored by tryptophan fluorescence and ANS binding
The data were fitted to a three-state transition model via a dimeric intermediate.
| ΔGN→I0 | mN→I | [Urea]1/2,1 | ΔGI→U0 | mI→U | [Urea]1/2,2 | ΔGN→U0 | |
|---|---|---|---|---|---|---|---|
| kcal/mol | kcal/mol/m | m | kcal/mol | kcal/mol/m | m | kcal/mol | |
| Tryptophan fluorescence | |||||||
| WT | 8.51 ± 0.46 | 1.81 ± 0.11 | 4.69 ± 0.06 | 5.91 ± 2.42 | 1.00 ± 0.36 | 5.91 ± 0.33 | 14.42 |
| A140D | 9.16 ± 0.82 | 2.02 ± 0.20 | 4.55 ± 0.09 | 5.14 ± 1.67 | 0.87 ± 0.26 | 5.94 ± 0.22 | 14.3 |
| ΔGlu-155/Glu-208 | 2.84 ± 0.79 | 1.48 ± 0.37 | 1.92 ± 0.12 | 5.78 ± 0.35 | 1.37 ± 0.08 | 4.22 ± 0.03 | 8.62 |
| ΔGlu-155/Lys-208 | 3.34 ± 0.97 | 1.80 ± 0.49 | 1.86 ± 0.11 | 5.39 ± 0.31 | 1.29 ± 0.07 | 4.19 ± 0.03 | 8.73 |
| ANS binding | |||||||
| WT | 7.65 ± 2.43 | 2.45 ± 0.80 | 3.11 ± 0.11 | 7.07 ± 0.42 | 1.44 ± 0.08 | 4.91 ± 0.03 | 14.72 |
| A140D | 5.43 ± 2.41 | 2.10 ± 0.91 | 2.58 ± 0.14 | 5.58 ± 0.57 | 1.13 ± 0.12 | 4.93 ± 0.06 | 11.01 |
| ΔGlu-155/Glu-208 | 3.51 ± 1.55 | 1.95 ± 0.77 | 1.77 ± 0.17 | 6.54 ± 0.58 | 1.55 ± 0.13 | 4.20 ± 0.04 | 10.05 |
| ΔGlu-155/Lys-208 | 3.89 ± 1.64 | 1.88 ± 0.79 | 2.06 ± 0.15 | 4.98 ± 0.62 | 1.27 ± 0.14 | 3.92 ± 0.07 | 8.87 |