Fig. 4. Diffusion characteristics of eYFP-H-Ras(N17) and eYFP-H-Ras(V12). Fitting of the square displacement distributions (Fig. 3) to Eqn 2 (Materials and methods) yielded a fraction of fast-diffusing molecules, , and corresponding characteristic mean square displacements for the fast (r₁²) and slow (r₂²) diffusing population of molecules for each t. A and D, B and E, C and F show plots of , r₁² and r₂², respectively, versus t_lag for both the N17 and V12 mutants. (A,D) The solid lines show the weighted mean of the fast fraction of molecules over all timelags. (B,E) Mean square displacement data of the fast-diffusing fractions were fitted according to a free diffusion model (r₁²=4D₁t_lag, solid line). (C,F) Mean square displacement data of the slow-diffusing fractions were fitted according to a free (C) and confined (F, Eqn 3) diffusion model (solid lines). The dotted lines in C and F represent the offset due to the limited positional accuracy (see Materials and Methods), although the same offset is present in B and 4E, the dotted lines were omitted here for clarity.