Table 2.
Thermodynamic and fluorescence parameters for ANS-binding to Ca2+-CaM proteins
| Protein | Temperature (°C) | Ka (M−1) | λmax (nm) | Fluorescence intensity at λmax (a.u.) |
|---|---|---|---|---|
| Ca2+-wt-CaM | 20 | 4.8 ± 0.3 × 103 | ||
| Ca2+-wt-CaM | 25 | 4.1 ± 0.1 × 103∗ | 481 | 166 |
| Ca2+-wt-CaM | 30 | 3.7 ± 0.2 × 103 | ||
| Ca2+-SeMet-CaM | 25 | 3.7 ± 0.3 × 103 | 485 | 134 |
| Ca2+-Eth-CaM | 25 | 3.2 ± 0.3 × 103 | 483 | 110 |
| Ca2+-Nle-CaM | 25 | 5.0 ± 0.3 × 103 | 479 | 285 |
| Ca2+-CT-CaM | 25 | 7.1 ± 0.2 × 103 | 474 | 332 |
| Ca2+-SeMet-CT-CaM | 25 | 6.2 ± 0.2 × 103 | 476 | 312 |
Apparent association constant (Ka) values were determined by ITC, and the steady-state fluorescence emission wavelength maximum (λmax) and fluorescence intensity at λmax (in arbitrary units, a.u.) were obtained from steady-state fluorescence emission spectra.
∗
Value represents the average and SD of three independent measurements. All other Ka error estimates are derived from curve-fitting uncertainties.