 HNTX-IV has a positively charged patch containing the amino acids Arg26, Lys27, His28, Arg29 and Lys32, of which Lys27, Arg29 and Lys32 are the most important for interaction with the TTX-S VGSCs.HNTX-V also shows an interface of positively charged amino acids that are responsible for the binding with the TTX-S VGSCs, where also Lys27 and Arg29 are the most important.Subtle differences in the positively charged patch can result in altered electrostatic properties, causing altered pharmacological effects.