Imidazole Complexes of Myoglobin and the Position of the Hæm Group

WE have prepared complexes of imidazole, 1-methyl imidazole and 4-methyl imidazole with various species of myoglobin, and crystallized them in forms previously described 1 ; the X-ray diffraction patterns of the crystals were then compared with those obtained from corresponding forms of metmyoglobin crystals. The results, which were similar for all three imidazoles, are summarized in Table 1. (In each case a large excess of imidazole was used: without this precaution combination is always incomplete.)