Binding affinity of Heloderma (A,B) and Varanus (C,D) crude venoms to the S3–S4 extracellular loop mimotope of domain IV of the human sodium channel NaV1.4. Figures (A,C) depict the area under the curve (AUC) of the curves displayed in figures (B,D). The Y axis of figure (B) shows the wavelength (nm) from the association (Ka binding) step. Asterisk symbols (*) above the bars (A,C) denote the level of statistical significance relative to the negative control. The negative control (-ve) was Naja kaouthia crude venom, while the positive control was Leiurus quinquestriatus crude venom. Dotted lines surrounding curves represent the error bars (B,D) based on SEM values from experiments performed in triplicate.