Lack of size and shape alteration of oxygenated and deoxygenated Lumbricus terrestris hemoglobin?

The giant extracellular hemoglobin of Lumbricus terrestris was investigated in the oxygenated, deoxygenated and reoxygenated state using small angle X-ray scattering. Scattering experiments of the oxygenated state of the protein yielded a radius of gyration of 10.71 +/- 0.02 nm, a maximum diameter of 29.37 +/- 0.21 nm and a volume of 6200 +/- 200 nm3. The values for the deoxygenated state of the hemoglobin are smaller than the values for the oxygenated state, but the differences hardly exceed the limits of error.