Studies on cobalt myoglobins and hemoglobins. XV. Thermodynamic properties of oxygen equilibrium of cobalt hemoglobin

Masao Ikeda-Saito, Daniela Verzili

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Oxygen equilibrium curves of cobalt hemoglobin were measured at five temperatures between about 5 ° and 25 °C in order to determine the enthalpy and entropy changes at each step of oxygenation. The averaged heat for oxygenation depends upon pH and anion conditions. The heat associated with each step of oxygenation is uniform under the given set of experimental conditions where cobalt hemoglobin binds oxygen co-operatively. The apparent non-uniformity vanishes after correction for the heat associated with the non-heme ligands, indicating that the intrinsic heat of oxygen binding is primarily uniform with respect to oxygenation steps. Two compensation processes were observed between the enthalpy and entropy changes corresponding to oxygenation of the low affinity and high affinity molecular species, which suggests that the compensation process is related to the co-operative oxygen binding in cobalt hemoglobin. The thermodynamic properties were compared with those of iron hemoglobin reported by Imai (1979) and Imai & Yonetani (1975b). The co-operative mechanism operating in cobalt hemoglobin is concluded to be essentially the same as that in iron hemoglobin with respect to its thermodynamic nature.

Original languageEnglish
Pages (from-to)441-449
Number of pages9
JournalJournal of Molecular Biology
Volume153
Issue number2
DOIs
Publication statusPublished - 1981 Dec 5

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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