Examination of Haldane's first law for the partition of CO and O2 to hemoglobin A0

✍ Scribed by Jeffries Wyman; Gary Bishop; Brough Richey; Robert Spokane; Stanley Gill

• Publisher: Wiley (John Wiley & Sons)
• Year: 1982
• Tongue: English
• Weight: 651 KB
• Volume: 21
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360210905

✦ Synopsis

Abstract

A study of the oxygen replacement reaction of carbon monoxide‐saturated hemoglobin (HbA~0~) was carried out using spectroscopic, calorimetric, and pH titration methods. Under fully saturated conditions the replacement reaction can be defined by a single partition constant over all ratios of bound oxygen to carbon monoxide. This indicates that under saturating conditions Haldane's first law for the ligand binding of gas mixtures holds for any CO/O~2~ ratio. It further shows that there is no appreciable difference in relative CO‐O~2~ affinity between the α‐ and β‐chains. The same partition coefficient was found to hold for different pH, buffer, and allosteric effector conditions. The lack of any pH dependence of the partition coefficient was confirmed by the absence of proton changes for the replacement reaction. The temperature dependence of the partition coefficient and calorimetric results yield a value for the enthalpy of the reaction of −3.65 ± 0.29 kcal/mol/heme.