The Effect of 2-Methoxy-5-nitrotropone on the Oxygen Affinity of Human Erythrocytes and Hemoglobin

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Abstract
Human Hb reacted with 2-methoxy-5-nitrotropoine at pH 7.4 underwent modification of the 4 N-terminal amino groups. The modified protein showed increased O2 affinity with complete abolition of the effect of D-glycerate 2,3-bisphosphate. The Bohr effect was abolished in the acid range and drastically reduced at alkaline pH values. Changes in the kinetics of ligand reactions paralleled the O2 equilibrium results. Cooperative effects were still present. Human erythrocytes treated with 2-methoxy-5-nitrotropone showed increased O2 affinity and some decrease in methemoglobin reductase efficiency but no change in resistance to hemolysis. The existence of changes in the O2 binding properties of human Hb as a result of chemical modifications of specific amino acid side chains suggests the possible use of chemical reagents in the therapeutic manipulation of the O2 affinity of human erythrocytes.