Photoswitchable materials could inspire the design of easy-to-deliver drugs, as demonstrated by Neil R. Branda and coworkers of Simon Fraser University, in Burnaby, British Columbia, who have used a bis(pyridinium) dithienylethene compound to induce paralysis in the worm Caenorhabditis elegans (J. Am. Chem. Soc., DOI: 10.1021/ja903070u). The molecule exists in one of two forms, depending on the wavelength of light it’s been hit with: Ultraviolet light switches it from a colorless, ring-open form to a blue, ring-closed isomer, and visible light causes the ring to reopen. The molecule maintains its photoswitching ability inside C. elegans and can be cycled multiple times. The researcher fed worms the ring-open form and observed that the worms behave normally. When the worms are hit with 365-nm UV light, the molecule converts to the ring-closed form and paralyzes the worms. Shining visible light longer than 490 nm on the worms reverses the paralysis, which is most likely caused by the ring-closed photoisomer disrupting the metabolic electronic pathway involved in energy production, Branda and coworkers note.