Table 1.
Summary of crystallographic analysis: Data quality and refinement
| Type | Resolution limit, Å | λ, Å | Rsym | (last shell) | Reflections | % complete | Detector (source) | Phasing power, Å |
|---|---|---|---|---|---|---|---|---|
| Native | 3.0 | 1.54 | 5.3 | (14.4) | 12,942 | 91 | Xentronics (Yale) | |
| Se-Met | 2.4 | 0.9794 | 4.8 | (18.0) | 10,852 | 82 | Mar image plate (ESRF) | 0.13 |
| Anomalous | 0.32 | |||||||
| Iodo-1* | 3.0 | 1.54 | 6.4 | (30.1) | 8,749 | 61 | Xentronics (Yale) | 0.75 |
| Iodo-2* | 2.9 | 1.54 | 10.0 | (39.0) | 13,234 | 92 | Raxis (Yale) | 0.65 |
| Iodo-3* | 3.0 | 1.54 | 6.4 | (24.2) | 12,986 | 90 | Xentronics (Yale) | 1.03 |
| Iodo-4* | 2.1 | 0.920 | 8.8 | (39.6) | 40,619 | 92 | CCD (CHESS A1) | 0.75 |
| Avg. figure of merit: 0.5 | ||||||||
| Resolution, Å | R factor | Free R factor | ||||||
| 40–2.1 (2σ data) | 21.2 | 26.8 | ||||||
| 40–2.1 (all data) | 22.8 | 28.2 | ||||||
| rms deviations | bond lengths 0.009 Å; bond angles 1.55° | |||||||
Rsym = Σ|Ih − 〈Ih〉|/ΣIh, where 〈Ih〉 is the average intensity over Friedel and symmetry equivalents. Phasing power = Σ|FH|/Σ∥FPHobs| − |FPHcalc∥. Anomalous phasing power = Σ|F"|/Σ∥ADobs| − |ADcalc∥, where AD is Bijvoet difference. CHESS, Cornell High Energy Synchrotron Source; CCD, charge-coupled device; ESRF, European Synchrotron Radiation Facility.
*
Crystals were grown with 5-iodouracil replacing thymine in the DNA at the following positions (Fig. 1 shows the numbering scheme). Iodo-1: 3, 4, and 5; Iodo-2: 9′ and 10′; Iodo-3: 6′, 7′, and 8′; and Iodo-4: 6′ and 7′.