The Orientation of Sickle Hemoglobin Fibers Within Bundles as Determined by Correspondence Analysis

Abstract

Sickle cell anemia results from the polymerization of deoxygenated sickle hemoglobin (HbS) into long helical fibers. In red blood cells, and in vitro, fibers aggregate and align to form bundles which eventually crystallize. The fiber bundles distort the red cells and have been implicated in the catalysis of the polymerization reaction. Although the structure of the HbS fiber has been extensively investigated, the packing of fibers in bundles and the fiber rearrangements which accompany crystallization are poorly understood, even though these phenomena are of interest at both a clinical and a basic level. We have used correspondence analysis to establish that during crystallization fibers separate into rows of particles oriented in opposite directions.Axial projections in opposite directions down the HbS fiber are different and are related by mirror symmetry. Thus they can be used to determine the particle orientation in or out of the plane of projection. Figure 1 shows these projections for models of an HbS fiber.