A method for estimating the surface charge of a cell by looking at its rate of movement in an electrical field. Most cells have a net negative surface charge, mostly due to carboxyl groups on terminal carbohydrate chains of glycoproteins and glycolipids. The cell is surrounded by a fluid layer in which the ionic composition is affected by the fixed charges on the membrane and the electrical potential measured (the electrokinetic or zeta potential) is actually some distance away from the plasma membrane. By varying the pH of the suspension fluid it is possible to identify the pK of the charged groups.
Subjects: Medicine and Health.