They came up with a process in which researchers engineer a tetracysteine sequence (Cys Cys Xaa Xaa Cys Cys) into a protein and expose cells to a small, biarsenical derivative of fluorescein called FLAsH, which is green under a fluorescent microscope. The two arsenics have a higher affinity for tetracysteine than for endogenous binding sites—higher even than that for the arsenic antidote, ethanedithiol (EDT), which is added to protect the cells and keep unbound FLAsH from fluorescing. Tsien's group has been creating numerous biarsenical ligands, and they recently demonstrated two: FLAsH, and red fluorescent ReAsH. By chasing one dye with another, the team was able to visualize the dynamics of connexin43 incorporation and turnover in gap junctions over time.
Gina Sosinsky of the National Center for Microscopy and Imaging Research at UCSD, brought the connexin problem to the table. Mark H. Ellisman, professor of neurosciences and the center's director says, ...
