Table 1

X-ray data collection and refinement statistics

Cd2+-DQAQB state (dark)Cd2+-D+QAQB state (light)Zn2+-DQAQB state (dark)
Data collection
 Maximum resolution, Å2.492.492.49
 Total unique observations (highest resolution shell)94,449 (13,013)92,263 (12,363)94,967 (12,576)
 Mean I/σ(I) (highest resolution shell)8.8 (3.6)7.0 (2.3)7.0 (2.3)
Rsym (highest resolution shell), %6.5 (21.0)8.9 (33.4)8.1 (32.8)
 Completeness§ (last shell), %99.1 (94.9)95.5 (88.4)96.7 (89.0)
 Resolution range, Å50–2.5050–2.5050–2.50
R factor, %22.722.623.8
Rfree, %25.725.226.5
 Deviation from ideal bond lengths, Å0.0120.0130.014
 Deviation from ideal bond angles, °
  • * Ratio of the total number of reflections measured to the total number of unique reflections. 

  • I/σ(I) is the ratio of the average of the diffraction intensities to the average background intensity. 

  • Rsym = ΣhklΣj|Ihkl − 〈Ihkl〉|/∑hklj|Ihkl|, where 〈Ihkl〉 is the average intensity for a set of j symmetry-related reflections and Ihklis the value of the intensity for a single reflection within a set of symmetry-related reflections. 

  • § Completeness is the ratio of the number of reflections measured to the total number of possible reflections. 

  • R factor = (∑hkl|Fo| − |Fc|)/∑hkl|FO| where |Fo| is the observed structure factor amplitude and |Fc| is the calculated structure factor amplitude. 

  • Rfree = (∑hkl,T|Fo| − |Fc|)/∑hkl,T|Fo|, where a test set, T (5% of the data), is omitted from the refinement.