Intermediates in the interconversion of acid and alkaline ferrihemoglobin. Structural and kinetic aspects.
The acid-alkaline pH-jump in suspension of crystalline sheep hemoglobin has been studied in the range of 5.95 to 8.94. Crystals suspended in 3.8 M Cs2SO4 show a rapid optical transition of half-time equal to or less than 2 ms. As the ammonia concentration is increased in the Cs2SO4-suspended crystals, a second optical transition is observed as a pseudo-first-order reaction, with a rate constant of between 10 and 15 s-1. The alkaline-acid pH-jump proceeds through a very rapid shift of the alkaline-acid equilibrium and is followed by a first-order dissociation constant between 9 and 12 s-1. The dissociation of the ammonia is biphasic, and the ratio between the fast and slow phases is 9.
D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D006454:Hemoglobins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008706:Methemoglobin; D008968:Molecular Conformation; D012756:Sheep; D013053:Spectrophotometry
D006454:Hemoglobins; D008706:Methemoglobin