Table 1.

Data collection and refinement statistics

Measurement	Value
Crystal data
a, Å	89.85 (91.17)*
b, Å	88.19 (88.06)*
c, Å	55.14 (55.25)*
β, °	97.8 (97.7)*
Space group	C2
Data processing
Resolution range, Å	12.0–2.0
No. of observations	64,025
No. of unique reflections	27,020
Completeness, %	92
Rmerge†	0.077
Refinement
Resolution range, Å	12.0–2.0
R factor‡	0.179
Rfree§	0.212
No. of protein atoms (αβ dimer)	2,136
No. of heme groups	2
No. of CO molecules	1
No. of water molecules	71
Root-mean-square deviations from ideal values
Bond lengths, Å	0.010
Bond angles, °	1.45
Dihedral angles, °	19.7
Improper angles, °	1.44

^*The values in parenthesis refer to HbTnCO crystals (PBD code 1T1N). 

^† R_merge = Σ_hklΣ_i|I_i − 〈I〉|/|I_i|. 

^‡ R factor = Σ_hkl(∥F_hklobs∥ − k|F_hklcalc∥)/Σ_hkl|F_hklobs|. 

^§ R_free = Σ_h(∥F_obs| − k|F_calc∥)/Σ_h|F_obs∥, where h is a statistical subset (10%) of data.