Direct Measurement of Diffusion in Olfactory Cilia Using a Modified FRAP Approach

The diffusion coefficient of fluorescein in detached cilia of Xenopus laevis olfactory receptor neurons was measured using spatially-resolved FRAP, where the dye along half of the ciliary length was photobleached and its spatiotemporal fluorescence redistribution recorded. Fitting a one-dimensional numerical simulation of diffusion and photobleaching for 35 cilia resulted in a mean value of the diffusion coefficient (1:20+0:23):10{10m2=s and thus a reduction by a factor of 3:4 compared to free diffusion in aqueous solution