FIGURE 1. TRPA1 activators.

This structural comparison illustrates the chemical diversity of TRPA1 activators. Macpherson et al.⁵ and Hinman et al.⁶ find that, despite their geometrical differences, several of these noxious substances act through the common mechanism of covalently attaching themselves to specific cysteine amino-acid residues on the TRPA1 ion channel.