| Sickle hemoglobin (HbS) is a genetic alteration of normal hemoglobin A (HbA). In HbS, a surface amino acid (b6) is transformed from charged (Glu) to hydrophobic (Val). This leads to the formation of multi-stranded polymers, which in turn are found in interconnected arrays called domains. The polymer stiffness and interconnections cause the cells containing such hemoglobin to become rigid, thereby blocking the microcirculation. Although the central problem of sickle cell disease is rheological, no experiments are known that can relate rheology at the cellular scale to the polymer formation that is its cause. A new technique has been developed to measure Rheology at microscopic scales that allow us to control polymer formation and characterize the formed domains at the same time. The created experimental apparatus and the established measurement techniques will be presented, results and their implication on our understanding of sickle hemoglobin rheology will be discussed. The unusual universality of sickle hemoglobin rigidity dependence on the amount of the formed polymer will be presented and discussed. |
