Inherently distorted heme as a novel tool for myoglobin-based oxygen carrier.

The two types of artificial myoglobins (Mbs) containing inherently distorted α-ethyl-2,4-dimethyldeuteroheme and undistorted 2,4-dimethyldeuteroheme were prepared to examine the influence of nonplanar heme deformation on the reactivity of Mb. In ferrous deoxy proteins, the paramagnetic proton nuclear magnetic resonance spectra showed that the deformed heme caused a 3.2-ppm lower-field shift of the proximal histidine signal, indicating a larger iron displacement from the heme plane upon the nonplanar deformation. The Mb with the nonplanar heme exhibited a markedly lower oxygen affinity as compared with the Mb containing the planar heme. The result suggests the utility of heme distortion to design the Mb-based oxygen carrier.