[Oxygen binding of hemoglobin following covalent fixation in the deoxy- and oxy- conformation]

Deoxyhemoglobin (deoxyHB) and oxyhemoglobin (HbO2) were covalently fixed to BrCN-activated Sephadex G-200. At pH 6, the oxygen semi-saturation pressure for the deoxyHb coupling product was 14.1, and for the HbO2 coupling product, 7.2 mm Hg. The alkaline Bohr effect delta was calculated to be - 0.55 and - 0.4 respectively. The Hill coefficients n are for both Hb derivatives between 1.4 and 1.5, independently of pH (for free Hb the respective values are pO2 50% = 18.2 mm Hg, delta = -0.55 and n = 2.5). Non-crosslinked dextran and Sephadex G-200 have no influence upon the affinity of free Hb to oxygen and upon cooperativity. As a reason for the varying oxygen-binding properties for the two Hb derivatives it is assumed that the amino group of valin alpha 1 is involved in the HbO2 fixation. In deoxyHb, this group is not probably converted. The reduced Hill coefficients and enhanced oxygen affinity are assumed to be due to impairment of the inter-chain contacts, to restrained cooperative mobility, and heterogeneity of the coupling products.