Estimating cytoplasmic diffusion coefficients. (A) A HEK cell expressing the R40L mutant of the PH-PLCδ1-GFP; the enlarged images show the strip of the cell imaged at the indicated times after bleaching. Bar, 10 µm. (B) Fluorescence intensity profiles across the bleached spot at the indicated times after bleaching; lines are fitted from the Gaussian function described in Eq. 3. (C) Increase in the square of the Gaussian width w with time is fitted in terms of the diffusion coefficient D using Eq. 4; see Materials and methods for details.