BIOPHYSICS. For the article “Determination of the binding sites of the proton transfer inhibitors Cd2+ and Zn2+ in bacterial reaction centers” by H. L. Axelrod, E. C. Abresch, M. L. Paddock, M. Y. Okamura, and G. Feher, which appeared in number 4, February 15, 2000, of Proc. Natl. Acad. Sci. USA (97, 1542–1547), the authors note the following correction. Under the Data collection heading of Table 1, the second subheading should read, “Total unique observations (highest resolution shell).” A corrected table is reprinted below.
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, Å | 2.49 | 2.49 | 2.49 |
| Total unique observations (highest resolution shell) | 94,449 (13,013) | 92,263 (12,363) | 94,967 (12,576) |
| Redundancy* | 3.9 | 3.9 | 3.9 |
| 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) |
| Refinement | |||
| Resolution range, Å | 50–2.50 | 50–2.50 | 50–2.50 |
| Reflections | 93,504 | 92,156 | 94,672 |
| R factor,¶ % | 22.7 | 22.6 | 23.8 |
| Rfree,∥ % | 25.7 | 25.2 | 26.5 |
| Deviation from ideal bond lengths, Å | 0.012 | 0.013 | 0.014 |
| Deviation from ideal bond angles, ° | 1.7 | 1.6 | 1.7 |
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〉|/∑hkl∑j|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.