Table 2

Anomalous diffraction differences and scattering factors for the CpI crystal used for MAD phasing (9). Observed diffraction ratios represent 〈Δ|F|21/2/〈|F|21/2, where Δ|F| is the absolute value of the Bijvoet differences at one wavelength (along the diagonal) or the dispersive difference between intersecting wavelengths (off-diagonal elements). An estimate of the noise in the anomalous signals is indicated by the Bijvoet differences for centric reflections shown in parentheses for each wavelength. The scattering factors were refined after multiple MADLSQ cycles (33); the f′ and f" values for the pre-edge wavelength (1.9074 Å) were fixed at the theoretical values, −2.18 and 0.55, respectively.

Wave- length (Å)Observed ratio (30.0 > d > 6.0 Å)Observed ratio (6.0 > d > 3.5 Å)Observed ratio (3.5 > d > 2.5 Å)Scattering factors (e)
1.90741.74181.73981.54981.90741.74181.73981.54981.90741.74181.73981.5498ff"
1.90740.0380.0890.0730.0380.0350.0580.0540.0340.0480.0690.0660.053–2.180.55
(0.020)(0.028)(0.038)
1.74180.0710.0320.1050.0430.0230.0580.0560.0410.079–8.132.59
(0.025)(0.027)(0.044)
1.73980.1070.0890.0590.0530.0760.075–7.433.80
(0.027)(0.030)(0.047)
1.54980.0850.0540.067–1.283.11
(0.028)(0.029)(0.043)