Electrostatic control of photoisomerization pathways in proteins

Abstract

Electrostatics guide chromophore twist Photoisomerization—the twisting of bonds in a molecule in response to absorption of light—is exploited in biology to sense light and can influence the photophysical properties of fluorescent proteins used in imaging applications. Romei et al. studied this behavior by introducing unnatural amino acids into the photoswitchable green fluorescent protein Dronpa2, thus systematically altering the electronic properties of the chromophore (see the Perspective by Hu et al. ). Crystal structures and spectroscopic analyses of a series of these variants support a model in which the electrostatic interactions between the chromophore and its environment influence the barrier heights for twisting around different bonds during photoisomerization. These insights may guide future design of photoswitchable proteins with desired properties. Science , this issue p. 76 ; see also p. 26