Qualitative evidence for higher affinity of MD-N2 for heme than N2.

<p>(A) Overlay of the spectra of 8 µM holo-N2, 8 µM holo-H64V/H68F myoglobin, and a mixture of 8 µM holo-N2 and 40 µM apo-H64V/H68F myoglobin. (B) Overlay of the spectra of 8 µM holo-MD-N2, 8 µM holo-H64V/H68F myoglobin, and a mixture of 8 µM holo-MD-N2 and 40 µM apo-H64V/H68F myoglobin. All the spectra were taken after 12-h incubation of the solutions at room temperature.