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Materials

Molecule Controls Worms With The Flip Of A Switch

Photoswitchable materials could inspire the design of easy-to-deliver drugs

by Celia Henry Arnaud
October 19, 2009 | A version of this story appeared in Volume 87, Issue 42

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Credit: J. Am. Chem. Soc.
UV light converts the photoswitchable molecule from a colorless, ring-open form to a blue, ring-closed form, paralyzing C. elegans worms in the process.
Credit: J. Am. Chem. Soc.
UV light converts the photoswitchable molecule from a colorless, ring-open form to a blue, ring-closed form, paralyzing C. elegans worms in the process.

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.

[+]Enlarge
UV light converts the photoswitchable molecule from a colorless, ring-open form to a blue, ring-closed form.
UV light converts the photoswitchable molecule from a colorless, ring-open form to a blue, ring-closed form.

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