The Effects of pH and Anions on the Properties of the 
and 
Chains within Human Deoxyhemoglobin
John S. Olson 1 and Quentin H. Gibson 1
From the
1 From the Section of Biochemistry and Molecular Biology, Cornell University, Ithaca, New York 14850
The reaction of n-butyl isocyanide with deoxyhemoglobin A has been examined as a function of pH and ionic strength in the presence and absence of inositol hexaphosphate. In solutions of high pH (about 9) or of low ionic strength at pH 7 the rates of n-butyl isocyanide binding to the 
and chains within deoxyhemoglobin are almost equal. At pH 7, increase of ionic strength decreases the rate of binding to chains. The addition of inositol hexaphosphate accentuates this effect, and in its presence the rates of binding and affinities of the chains are substantially reduced in relation to the corresponding chain values. Although it is known that organic phosphates bind between the chains (Arnone, A. (1972) Nature 237, 146–149), the main effect of inositol hexaphosphate is a modification of the ligand-binding properties of the chains. Similarly, the addition of protons to solutions of deoxyhemoglobin exerts a greater effect on the functional properties of the chains than on the chains, even though, at neutral pH 50% of the additional number of protons bound to deoxyhemoglobin are associated with the imidazole group of histidine 146 (Kilmartin, J. V., and Wootton, J. F. (1970) Nature 228, 766–767). These results show that the functional properties of hemoglobin cannot be explained solely in terms of the perturbation of a single microscopic conformational equilibrium since the properties of the individual and chains within deoxyhemoglobin are unequally influenced by anions and protons while those of liganded hemoglobin are not.
Submitted on August 29, 1972
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