Locked-Azobenzene: Testing the Scope of a Unique Photoswitchable Scaffold for Cell Physiology.

Azobenzenes are the most widely studied photoswitches, and have become popular optical probes for biological systems. The cis configuration is normally metastable, meaning the trans configuration is always thermodynamically favored. The unique exception to this rule is an azobenzene having a two-carbon bridge between ortho positions, substitutions that lock the photoswitch in its cis configuration. Only thoroughly chemically characterized relatively recently, we describe the first applications of this locked-azobenzene (or "LAB") scaffold with two derivatives designed to control ion flow in pyramidal neurons in acutely isolated brain slices. Our LAB derivatives maintain most of the desirable photochemical properties of the parent scaffold, and work as designed in living cells. However, LAB derivitization changes the trans photostationary state from >85% of the parent photoswitch to about 50%, suggesting that careful design considerations must be given for future applications of the LAB scaffold in biological areas.