Table 2.

X-ray data. Refinement statistics for the three nitrile-modified RNase S variants with data for the highest resolution shell in brackets, all three solved in the C₂ space group.

Molecule	pCN-RNase	mCN-RNase	SCN-RNase
Resolution [high res. shell]	1.5 Å [1.49-1.54 Å]	2.5 Å [2.50-2.56 Å]	2.3 Å [2.30-2.36 Å]
# of reflections [high res. shell]	36722 [2652]	7887 [560]	9888 [686]
% possible [high res. shell]	95.8 [92.4]	99.9 [100]	95.8 [95]
Redundancy [high res. shell]	4.5 [3.2]	3.2 [3.2]	1.8 [1.9]
Rworka	0.205	0.209	0.218
Rfreea	0.225	0.271	0.271
Cα RMSDb (A chain / B chain)	0.37 / 0.32 Å	0.42 / 0.37 Å	0.37 / 0.46 Å
Local RMSDc (A chain / B chain)	0.23 / 0.21 Å	0.31 / 0.10 Å	0.52 / 0.26 Å

^aR_free and R_work are the R-factors ($R=\frac{\Sigma |F_{\mathit{obs}}-F_{\mathit{calc}}|}{\Sigma \left|F_{\mathit{obs}}\right|}$ where F are the observed or calculated X-ray structure factors) for two randomly selected subsets of the reflection data. 95% of the total F_obs data points are used to guide refinements to the model (minimizing R_work), while 5% are set aside to evaluate the improvement (R_free).

^bThe average root-mean-square deviation for all backbone carbon atoms for one molecule of the two molecule asymmetric unit, calculated against a set of published RNase structures of different space groups (7RSA and 1DY5 = P2₁, 1RNU = P3₁2 ). The average RMSD for the members of the comparison set relative to each other is 0.36 Å.

^cRMSD of all the atoms in the 5 Å neighborhood of the nitrile (excluding the substituted amino-acid) relative to the same atoms in the comparison set. The average RMSDs for the comparison set relative to each other are 0.22, 0.24 / 0.13 and 0.17 Å for pCN, mCN (A /B) and SCN neighborhoods respectively.