期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：9
页码：3382-3386
DOI：10.1073/pnas.72.9.3382
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have examined the redox equilibria of azidomethemoglobin (low-spin) and fluoromethemoglobin (high-spin). We have derived a modified Hill equation which includes the tetramer--dimer equilibrium of the oxidized form, and also generalized the two-state model to incorporate ligand binding to the ferriheme. The pH dependence of the redox Hill's constant for fluoromethemoglobin is the same as that for methemoglobin, demonstrating that this dependence and the marked cooperativity achieved (n = 2.2) are not coupled to changes of the ferriheme spin state. The redox Hill's constant for azidomethemoglobin, however, is as large as the oxygenation Hill's constant (n approximately 2.7) and is also roughly pH independent.
