Reversibly switchable fluorescent proteins (RSFPs) are molecules that switch to a new fluorescent state in response to irradiation with light of a specific wavelength. RSFPs have attracted widespread interest for emerging techniques including repeated tracking of protein behavior and superresolution microscopy. Among the limited number of RSFPs available, only Dronpa is widely employed for most cell biology applications due to its monomeric and other favorable photochemical properties.

Recently,Professor Xu Tao and Professor Xu Pingyong at the Institute of Biophysics, Chinese Academy of Sciences discovered a unique strategy for generating RSFPs of different optical characteristics by mutating the first position of chromophore residues, but not the sites in the vicinity of the chromophore. They developed a series of  green RSFPs with beneficial optical characteristics such as high photon output per switch, high photostability, a broad range of switching rate, and pH-dependence, which make them potentially useful for various applications. One member of this series, mGeos-M, exhibits the highest photon budget and localization precision potential among all green RSFPs. They propose mGeos-M as a candidate to replace Dronpa for applications such as dynamic tracking, dual-color superresolution imaging, and optical lock-in detection. The distinguished properties of developed mGeos expanded the current tool kit of PAFPs and allow for broad applications in dynamic live cell imaging and superresolution imaging.

This work was published in the latest issue of PNAS and supported by the Ministry of Science and Technology of China, the National Science Foundation of China and the Chinese Academy of Sciences.