[The effect of the immobilization of hemoglobin on its oxygen binding]

Hemoglobin (Hb) covalently fixed to CM-Sephadex was found to bind oxygen in weakly acidic medium with higher affinity than free Hb. The opposite relation is seen in the alkaline pH region. The alkaline Bohr effect was determined to be -0.2 only. Cooperativity is pH dependent. The sigmoid coefficient at pH 6 is 0.7; at pH 8.7 n was determined to be 1.3. As the reason of these altered binding properties a blockade of the primary amino groups, disturbance of the salt bridges, and restrained cooperative mobility of the Hb-subunits are discussed. The Hill coefficient is additionally lowered by the heterogeneity of the immobilized Hb.