Figure 3.

NSB depends on the extent of ligand depletion and cannot be calculated from apparent NSB. A. Total binding is shown when ligand depletion is negligible with increasing values of α ranging from 0 to 1 (integer log values of α from -7 to 0; legend for A-C in B). α = 0 is line with horizontal plateau at large concentration of [3H]EB. B and C. Similar to A except ligand depletion is substantial (R1T = 0.3 nM) or extreme (R1T = 300 nM). The effects of a particular α value on total binding depend on the extent of ligand depletion. D, E, F. NSB on expanded y-scales shows how increasing ligand depletion affects NSB (legend for α in F; integer log values from -7 to 0). G. Specific binding is not calculated correctly as the difference between total binding and apparent NSB when ligand depletion is significant. Solid black line: apparent NSB obtained without α4β2 nAChR. Lines for total binding at increasing concentrations (nM) of R1T and, therefore, increasing ligand depletion appear above apparent NSB. Corresponding lines for NSB when α = 0.1 are below apparent NSB. H. NSB (same code for lines as in G) and apparent NSB (solid line) from G are shown with an expanded y-scale. Binding in this figure was calculated with two sites modelfree.

Person and Wells BMC Biophysics 2011 4:19   doi:10.1186/2046-1682-4-19
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