(A) The binding of biotinylated LF to immobilized TSP. TSP was immobilized to microtiter wells. The biotinylated-LF binding to the immobilized TSP (•) was examined. The same assay was conducted omitting TSP (▵). Each point represents the mean ± SD of triplicate determinations. (B) Inhibition of biotinylated-LF binding to immobilized TSP by unlabeled LF. Biotinylated LF binding to immobilized TSP was examined in the presence of the indicated concentrations of unlabeled LF. Absorbance at 405 nm obtained in the absence of TSP was subtracted, and the results are expressed as a percentage of the binding in the absence of inhibitor. The average A405 obtained by biotinylated LF binding to TSP in the absence of unlabeled LF was 0.26. Each point represents the mean ± SD of triplicate determinations.