Structure determination of porcine haemoglobin

To investigate a potential candidate material for making artificial red blo od cells to supplement blood transfusion, the X-ray structure of porcine ha emoglobin at 1.8 Angstrom resolution was determined as part of research tow ards synthesizing human blood. Porcine haemoglobin was crystallized by the vapor-diffusion method, producing crystals of dimensions 0.3-0.5 mm after s uccessive seeding. The crystals belong to the orthorhombic space group P2(1 )2(1)2(1), with unit-cell parameters a = 68.10, b = 72.27, c = 11885 Angstr om. The initial phase was determined by the molecular-replacement method, u sing human oxyhaemoglobin as a model, The final R factor was 21.1% for 36 8 20 reflections after validation of 574 water molecules, The r.m.s. deviatio ns of bond lengths, angles, torsion angles and improper angles from their i deal values are 0.017 Angstrom, 3.0, 20.6 and 1.8 degrees, respectively. Th e average B factor is 33.63 Angstrom(2) for the haemoglobin molecule and 50 .53 Angstrom(2) for the water molecules. The structure could be superimpose d on a 2.8 Angstrom resolution structure with an r.m.s. difference of 0.59 Angstrom in main-chain atomic positions and 1.27 Angstrom in side-chain ato mic positions. Porcine and human haemoglobins are compared. A tentative mod el for artificial blood is proposed based on the complementarity relationsh ip of the surface charges between haemoglobin and the surrounding cell memb rane.