Medicinal Chemistry & Chemical Biology, Short talk
MC-012

Photoactivation of silicon rhodamines via a light-induced protonation

M. S. Frei1,2, L. Reymond3,4*, K. Johnsson1,2*
1Institute of Chemical Sciences and Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland, 2Department of Chemical Biology, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany, 3Biomolecular Screening Facility, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland., 4National Centre of Competence in Research (NCCR) in Chemical Biology, 1015 Lausanne, Switzerland

Photoactivatable fluorophores are important tools to investigate dynamic processes in cells. With the advent of super-resolution microscopy techniques based on single-molecule localization, these fluorophores have found even more applications. However, to make these techniques available for routine live-cell imaging, brighter, cell-permeable fluorophores are required. In our research, we develop new photoactivatable synthetic fluorophores based on the silicon rhodamine scaffold. This class of fluorophores has ideal properties for live-cell imaging: excitation and emission maxima in the far-red, high extinction coefficient, high quantum yield, photostability and cell-permeability. Instead of using bulky photolabile groups, we made use of photochemical concepts that require smaller structural modifications and generated a far-red photoactivatable fluorophore. The unusual mechanism of photoactivation and the fluorophore’s outstanding spectroscopic properties make it a powerful tool for live-cell super-resolution microscopy. We showed that this fluorophore can be used not only in fixed-cells, but also for following the fast dynamics of mitochondria by single-molecule localization microscopy in live-cells. Most excitingly, we could distinguish the unlabeled interior of the mitochondria from their labeled outer membrane in several cases, showcasing the power of this probe in combination with super-resolution microscopy.