In the article "Equilibrium Binding of [ 3 H]Tubocurarine and [ 3 H|Acetylcholine by Torpedo Postsynaptic Membranes: Stoichiometry and Ligand Interactions" by Richard Neubig & Jonathan Cohen. Explain what is happening in figure 5 in 1-2 paragraphs.

NEUBIG AND COHEN FIGURE 5: dTC inhibition of the initial rate of binding of 3H-labeled N. nigricollis -toxin to T. californica membranes. Equal (4 mL) volumes of TPS 0.1%BSA containing 2nM-toxin sites and 12nM 3H-labeled N. nigricollis -toxin were preincubated for 30min at 22 C with various concentrations of dTC. The binding reaction was initiated by mixing the two solutions, and then 1-mL aliquots were filtered on Millipore GS filters at 20-120-s intervals. Filtration intervals were selected for each dTC concentration so that seven data points could be obtained during the linear phase of the binding reaction, and the seven values of counts per minute bound vs. time were fitted by a linear least-squares program to determine the slope SD. Error bars for control values (no drug) are the standard deviation of triplicate determinations, and those for experimental points are the combined error from control values and the SD of the least squares fitted slope. Data are from experiments in three preparations (,0,) of membranes; control values of initial rate (Vio) correspond to bimolecular association constants of (1.21.8)107M1min1. The solid line is the expected inhibition pattern for a single hyperbolic binding site with KD=56nM, and the dashed line is for two sites present in equal amounts with Kd1=15nM and Kd2=7M