FIGURE 1.

(A) Fluorescence microscopic images at indicated time points from a conventional FRAP, showing nearly full recovery of the fluorescence intensity inside the lipid bilayer bleached spot to the prebleach level in ∼2 min (upper row), from a contact-area FRAP for the CD2-CD58 system, showing nearly full recovery in ∼5 min, despite the higher fluorescence intensity within the contact area (middle row), and from a contact-area FRAP for the CD16a^GPI-RbIgG system, showing a much slower time course of fluorescence recovery that is incomplete, although a steady state had apparently been reached (lower row). The gray-scale levels of different rows have been adjusted to accommodate their different dynamic ranges. See Tolentino et al. (24) for experimental methods. (B) Comparison between the measured (points) and predicted (curves) FRAP time courses. The fluorescence intensities were normalized by those of the free ligands outside of and far away from the contact area. The theoretical curves were fits of solutions of Eqs. 5–8 to the data. For the conventional FRAP problem, the only dependent variable of interest is m_l and the mathematical model is obtained from Eq. 5 by setting the kinetic rates to zero and ξ to unity. Note that the timescale of the CD16b^GPI-RbIgG case (upper abscissa) is six times that for the other two (lower abscissa).