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Figure 4.
Figure 4. The heme pocket of metMb at pH 4 (white), 5 (yellow) and 6 (red). On the distal side at pH 4, the movement
of the water molecule ligand and His64 is similar to that in the deoxyMb structure at pH 4 due to the protonation of
the group (Figure 1(b)). On the proximal side, His93 undergoes significant conformational changes and the distance
from the iron atom to N
e
of His93 is 2.5 Å , representing either a weakened bond or the breakage of the bond in some
molecules in the crystal. The =2Fo - Fc= electron density map is contoured at 1.5 standard deviations above the average
density of the map for metMb at pH 4.
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