Hemoglobin polymerization in sickle cells studied by circular polarized light scattering
We have studied intracellular polymerization of hemoglobin S in suspensions of small populations of sickle cells using circular polarized light scattering. We argue that the preferential scattering of right circular polarized light (as expressed by measurements of the S14 Mueller scattering matrix element) directly reflects the amount of polymer inside cells. This technique has made it possible to investigate the effect of oxygen tension, cell density and osmotic stress on intracellular hemoglobin polymerization. Using S14 to determine hemoglobin polymer, we show that the polymer increases with deoxyhemoglobin concentration, that cells containing higher hemoglobin concentrations show significantly more polymer than cells containing less hemoglobin, and that polymerization occurs in sickle-trait cells in hypertonic solutions as the oxygen tension in the suspension is reduced. We also present kinetic measurements of polymerization, including that induced by osmotic shock. Finally, we demonstrate that the total light scattered (S11 Mueller scattering matrix element) that is routinely measured simultaneously with S14 can be used to estimate the percent of reduced (deoxy) Hb in the sample. These experiments demonstrate the potential of this technique to monitor hemoglobin polymerization simultaneously with oxygen dissociation under a wide variety of physiological conditions.