TABLE 2.
Iron spin states and H2O2-induced protein radical yield in various ferric samples
The percent high spin was calculated from the ratio of the high spin EPR signal at 10 K to the signal recorded in the presence of 0.1 m NaF. The percent low spin was calculated from subtracting this value from 1. Fluoride failed to convert the high-spin heme in AHSP·α. The percent radical intermediate yield was determined based on a Cu(II) standard measured at 115 K. Percentage high-spin heme for AHSP·α was estimated using average signal height at g = 6 for the fluoride complex of both purified α- and β-subunits. These experiments were repeated several times using slightly different experimental conditions (e.g. microwave power, modulation amplitude, etc.).
| Ferric sample | Resting state high spin | Resting state low spin | H2O2-generated radical yield |
|---|---|---|---|
| % | |||
| α | 22.5 | 77.5 | 1.7 |
| AHSP·α | <10 | >90 | 0.078 |
| β | 21.5 | 78.5 | 4.3 |
| HbA | 76.4 | 23.6 | 5.5 |
| Hp·αβ | 83.3 | 16.7 | 4.8 |