“…With the capability of probing transport over length scales as small as a few micrometers, fluorescence recovery after photobleaching (FRAP) is particularly well suited for measuring slow diffusion and diffusion in confined regions. This technique is therefore frequently applied to biological systems (e.g., Golan and Veatch, 1980;Jacobson and Wojcieszyn, 1984;Elson, 1986;Koppel, 1986), most commonly the cell membrane and cytoplasm. It also has been applied to Langmuir-Blodgett films (Weiss et al, 1982;Wright et al, 1988;Pachence et al, 1990), polymer films (Smith, 1982), and lipid bilayers (Smith et al, 1979) as well as to proteins adsorbed at the solid-liquid interface (Burghardt and Axelrod, 1981;Tilton et al, 1990a,b; Rabe and Tilton, 1993;Gaspers et al, 1994).…”