Receptor occupancy on an ellipsoidal cell in the presence of a point source of a chemoattractant

Diffusion of a chemoattractant from a micropipet is routinely used to examine the different aspects of a cell's chemotactic response. To quantify the effect of cell elongation on chemotactic sensitivity in the micropipet assay, the chemoattractant concentration at the cell plasma membrane was determined by solving the equation for diffusion from a point source in the presence of a prolate ellipsoid of varying eccentricity. The results show that cell elongation can significantly increase the difference in receptor occupancy between near and far cell ends and thereby enhance the sensitivity of chemotactic cells to shallow chemoattractant gradients.