Table 1.

Data collection and refinement statistics

Data collection	d(CGCGCG)2–Cr3+
Radiation source	14.2 BESSY Berlin
Wavelength (Å)	0.9184
Temperature (K)	100
Space group	P212121
Cell dimensions (Å)	a = 18.14, b = 30.44, c = 42.94
Resolution range (Å)	24.83–0.97 (1.00–0.97)a
Number of reflections	14,037b/26,535c
Completeness (%)	98.4 (93.2)c
Redundancy	2.53 (2.14)c
<I/σI>	24.85 (2.05)c
R dmerge (%)	1.6 (43.2)c
Wilson B-factor (Å2)	4.87
Refinement
Refinement program	SHELXL
Resolution (Å)	24.83–0.97
No. of reflections in working set	13,028b/24,677c
No. of reflections in test set	1009b/1856c
R/R efree (%)	14.47c/18.49c
No. of atoms (nucleic acid/metal/solvent)	240/3/67
<B eq> (Å2) (nucleic acid chain A/B/metal/solvent)	17.5/13.4/13.7/23.7
R.m.s. deviations from ideal
Bond lengths (Å)	0.019
Bond angles (°)	1.93

^aValues in parentheses correspond to the last resolution shell

^bBijvoet pairs merged

^cBijvoet pairs separate

^d $R_{\text{merge}}={\mathit{\Sigma }}_h{\mathit{\Sigma }}_j\left|I_j^h-〈I^h〉\right|/{\mathit{\Sigma }}_h{\mathit{\Sigma }}_j{I}_j^h$, where $I_j^h$ is the intensity of observation j of reflection h

^e $R={\mathit{\Sigma }}_h\left|\left|F_{\text{o}}\right|-\left|F_{\text{c}}\right|\right|/{\mathit{\Sigma }}_h\left|F_{\text{o}}\right|$ for all reflections, where F _o and F _c are observed and calculated structure factors. R _free is calculated analogously for a random subset of reflections excluded from the refinement