Measurement of Rate Constants for Reactions of O2, CO, and NO with Hemoglobin

The kinetics of O₂ , CO, and NO binding to mammalian hemoglobins (Hbs) have been studied for 75 yr, starting with the original rapid mixing experiments of Hartridge and Roughton (1 ). Over the last 20 yr, these measurements have been extended to time scales ranging from hours to picoseconds. Numerous articles have been written about rapid mixing and photolysis instruments, methods for defining specific association and dissociation rate constants, and algorithms for analyzing the results in terms of specific models for cooperative ligand binding (2 –10 ). A comprehensive review of these techniques and methods, however, is beyond the scope of this book. Instead, a practical guide to determining rate constants for O₂ , CO, and NO binding to native and recombinant Hbs is presented, with a special emphasis on tetrameric adult human Hb (HbA).