Table 1.
Order parameters and other fitting parameters determined from the 15N relaxation data for His side-chain Nδ1H groups.
| His25 | His53 | |
|---|---|---|
| Relaxation data at 800 MHza) | ||
| 15N R1 [s−1] | 0.76 ± 0.04 (0.79) | 0.74 ± 0.05 (0.77) |
| [1H-]15N NOE | 0.79 ± 0.06 (0.81) | 0.85 ± 0.06 (0.85) |
| ηxy [s−1] | 15.8 ± 1.2 (16.5) | 15.6 ± 1.1 (16.2) |
| ηz [s−1] | 0.50 ± 0.10 (0.50) | 0.45 ± 0.09 (0.48) |
| Relaxation data at 600 MHza) | ||
| 15N R1 [s−1] | 1.03 ± 0.02 (0.97) | 1.05 ± 0.03 (1.00) |
| [1H-]15N NOE | 0.76 ± 0.04 (0.73) | 0.82 ± 0.04 (0.82) |
| ηxy [s−1] | 12.6 ± 0.5 (12.5) | 12.1 ± 0.6 (12.3) |
| ηz [s−1] | 0.62 ± 0.07 (0.60) | 0.73 ± 0.04 (0.62) |
| Fitting parametersb) | ||
| S2 | 0.91 ± 0.04 | 0.98 ± 0.07 |
| τi [ns] | 1.0 ± 0.3 | 0.3 ± 0.4 |
| Δσ [ppm] | −207 ± 22 | −213 ± 22 |
| θ [°] | 29 ± 4 | 29 ± 2 |
a)
Values in parentheses are those from the fitting calculations. ηxy, the CSA–DD cross-correlation rate; ηz, CSA–DD cross-correlation rate.
b)
S2, the generalized order parameter; τi, the correlation time for internal motion; Δσ, the effective 15N CSA; θ, the angle between the 15N CSA main principal axis and the Nδ1H bond. The molecular rotational correlation time τr = 13.9 ns and the rotational anisotropy (D||/D⊥) of 1.59 from the previous study3 were used for the fitting calculations. The Monte Carlo method21 was used to estimate uncertainties.