. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIELD-INDUCED AChR REDISTRIBUTION 159 diffusion (Jaffe, 1977; Poo ct a/.. 1979; McLaughlin and Poo, 1981). The density of sites as a function offl(Q)is Q = fm • a • e\p(-fi • cos 6) + (1 - fm) • C,, where tt = 0-Cj/sinh(0), 0 = , r is the cell radius. C, the initial molecular concentration, E the field strength, fm the fraction of mobile sites, m the electromigration mobility constant, and D the diffusion constant (Stollberg and Fraser, 1988). The two parame- ters m/D and fm were allowed to vary in fitting this mo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FIELD-INDUCED AChR REDISTRIBUTION 159 diffusion (Jaffe, 1977; Poo ct a/.. 1979; McLaughlin and Poo, 1981). The density of sites as a function offl(Q)is Q = fm • a • e\p(-fi • cos 6) + (1 - fm) • C,, where tt = 0-Cj/sinh(0), 0 = , r is the cell radius. C, the initial molecular concentration, E the field strength, fm the fraction of mobile sites, m the electromigration mobility constant, and D the diffusion constant (Stollberg and Fraser, 1988). The two parame- ters m/D and fm were allowed to vary in fitting this model to data (all other parameters being measured quantities). Results Methodological considerations As shown previously, the video-microscopic assay is linear over a substantial range of ligand concentrations, and after the pixel-by-pixel correction scheme (see Mate- rials and Methods), the assay is independent of pixel po- sition within the image (Stollberg and Fraser, 1988). The same study also indicated that the binding of fluorescent ligands is independent of binding-site density over the range of densities encountered in these experiments. Analysis of experiments was performed only when the data were within the linear range of the assay. Concanavalin A binding sites FLR-con A labeled sites were seen to migrate towards the cathode-facing pole of cells in electric fields. The time-course of asymmetry development in the electric field is well fit by an exponential with r = 12 min (Stoll- berg and Fraser, 1988), and is close to maximal after 40 min. The steady-state distributions of FLR-con A bind- ing sites following fields of 0, 1,2, and 4 V/cm for 40 min are shown in Figure 2. The solid lines represent the least- squares fit of the theoretical model (see Materials and Methods) to the four experimental conditions. The fig- ure illustrates a good agreement between data and the theory over this range of field strengths (Fig. 2, legend). After termination of a field of
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
