Table 2. Procedure and statistics for the structure refinement.

Refinement step/program	Additions	Resolution (Å)	R factor (%)	Free R (%)
REFMAC	Rigid molecule	20–2.0	26.8	28.0
	Atomic positions	20–0.8	21.6	21.1
	Solvent	20–0.7	16.0	15.6
	Isotropic ADPs	20–0.7	13.7	13.7
SHELXL	Double conformers	20–0.7	13.8	—
	H atoms	20–0.7	13.2	—
	Anisotropic ADPs	20–0.65	9.1	—
	All	20–0.65	7.9	—
MoPro	Solvent correction	20–1.50	—	—
	Anisotropic ADPs†	20–0.55	13.6	—
	Valence population	20–0.55	13.6	—
	Expansion coefficients	20–0.48	13.3	—
	Multipoles	20–0.48	12.7	—
	All	20–0.48	12.7	—

^†Also performed in a round of high-order refinement at 1.0–0.5 Å to prepare for subsequent steps.