Electrophoretic Studies on Red Cells

These experiments were made to obtain more information about the surface of the red blood cell. Since "surface" means different things to different people, we shall define our meaning now. Strictly speaking, the surface studied by electrophoresis is the surface of shear between the cell (moving in the electric field) and the surrounding medium, for it is the potential at this surface which is the electrokinetic potential. But since this potential has its origin in the charged groups possessed by the cell membrane, we shall broadly use the term surface (unless we say otherwise) to mean that part of the membrane possessing these charged groups. That part of the membrane may be limited to the outermost constituent molecules of the membrane (i.e., to those molecules just inside the surface of shear), but we have no direct evidence of this. Also we have no data on the variations of charge density in different portions of the surface. The electrophoresis studies in this paper are divided into three parts. First, we have determined the mobility of human red cells as a function of the ionic strength at approximately constant pH. Secondly, we have determined the mobility as a function of pH at constant ionic strength for intact red cells, for the lipid of the red cell stroma, and for the protein of the stroma. Finally, we have determined the mobility of cells and ghosts under experimental conditions which cause changes in the mobility.