Distal and proximal control of ligand reactivity, a transient Raman comparison of COHbA and COHb (Zurich).

Using Raman scattering, it is shown that for a given solution conditions the quantum yield of photolysis averaged over a 10 ns laser excitation pulse is consistently lower for COHb (Zurich) than for COHbA. In going from pH 8.2 to pH 6.2 +3mM IHP both hemoglobins exhibit the same proportional increase in the photolysis yield. The transient Raman spectrum of these photolyzed carboxy hemoglobins indicates that the behavior and geometry of the proximal side of the heme is very nearly the same in both proteins.