Structure determination and refinement statistics.

aValues in parenthesis are for the highest resolution shell. Rsym = Σ|I-|/Σ(I), where I is the observed integrated intensity, is the average integrated intensity obtained from multiple measurements, and the summation is over all observable reflections. Rcryst = Σ||Fobs|-k|Fcalc||/Σ|Fobs|, where Fobs and Fcalc are the observed and calculates structure factors, respectively. Rfree is calculated as Rcryst using 5% of the reflection chosen randomly and omitted from the refinement calculations. Bond lengths and angles are root-mean-square deviations from ideal values.