-fold excess biotin was added, compared to the biotin-binding sites available on the beads). Fluorescence emitted by each Vβ-immobilized bead due to toxin binding, was plotted on bar graphs: Vβ-SEA (purple), Vβ-SEB (orange), Vβ-TSST-0 (blue), Vβ-SpeA (red) and Vβ-SpeC (green).  (TIFF)  ######   Click here for additional data file.  ###### Effect of blocking Vβ-immobilized beads with biotin on multiplex assay in the presence of a mixture of toxins.