Crystallization and X-ray diffraction data analysis of human deoxyhaemoglobin A(0) fully stripped of any anions

In this work, initial crystallographic studies of human haemoglobin (Hb) cr ystallized in isoionic and oxygen-free PEG solution are presented. Under th ese conditions, functional measurements of the O-2-linked binding of water molecules and release of protons have evidenced that Hb assumes an unforese en new allosteric conformation. The determination of the high-resolution st ructure of the crystal of human deoxy-Hb fully stripped of anions may provi de a structural explanation for the role of anions in the allosteric proper ties of Hb and, particularly, for the influence of chloride on the Bohr eff ect, the mechanism by which Hb oxygen affinity is regulated by pH. X-ray di ffraction data were collected to 1.87 Angstrom resolution using a synchrotr on-radiation source. Crystals belong to the space group P2(1)2(1)2 and prel iminary analysis revealed the presence of one tetramer in the asymmetric un it. The structure is currently being refined using maximum-likelihood proto cols.