Chemotactic factor concentration gradients in chemotaxis assay systems.

In most assays of chemotaxis the gradient of the chemotactic factor is established and later destroyed by its diffusion through some matrix. The characteristics of the gradient depend upon the geometry of the assay system, the diffusion coefficient of the chemotactic factor and the concentration of the chemotactic factor added. We have solved the diffusion equations to characterize the gradients present in 3 assays of chemotaxis in current use: the millipore, under-agarose and visual assay systems. In each case of the solutions are presented for various assay times and for chemotactic factors with various diffusion coefficients.