2-D membrane diffusion model grid. White ellipse represents the disc perimeter, and red lines indicate incisure positions traced onto the grid from the image of a rod outer segment on which an mFRAP experiment was performed. The Gaussian intensity profile represents the initial distribution of photoconverted molecules, and the flux at the disc perimeter and incisure grid points are set to zero. Diffusivities at all other grid points within the ellipse may be set arbitrarily; for this study, they were assumed to be uniform and equal to the empirically derived D_lat of Rho-EGFP (see Fig. 6).