Stable Transfection of the Singlet Oxygen Photosensitizing Protein SOPP3: Examining Aspects of Intracellular Behavior^†

Abstract

Protein-encased chromophores that photosensitize the production of reactive oxygen species, ROS, have been the center of recent activity in studies of oxidative stress. One potential attribute of such systems is that the local environment surrounding the chromophore, and that determines the chromophore's photophysics, ideally remains constant and independent of the global environment into which the system is placed. Therefore, a protein-encased sensitizer localized in the mitochondria would arguably have the same photophysics as that protein-encased sensitizer at the plasma membrane, for example. One thus obtains a useful tool to study processes modulated by spatially localized ROS. One ROS of interest is singlet oxygen, O 2 (a 1 D g ). We recently developed a singlet oxygen photosensitizing protein, SOPP, in which flavin mononucleotide, FMN, is encased in a re-engineered lightoxygen-voltage protein. One goal was to ascertain how a version of this system, SOPP3, which selectively makes O 2 (a 1 D g ), in vitro, behaves in a cell. We now demonstrate that SOPP3 undergoes exacerbated irradiation-mediated bleaching when expressed at either the plasma membrane or mitochondria in stable cell lines. We find that the environment around the SOPP3 system affects the bleaching rate, which argues against one of the key suppositions in support of a proteinencased chromophore.

Imparting Stability to Organic Photovoltaic Components through Molecular Engineering: Mitigating Reactions with Singlet Oxygen

“…In N 2 ‐saturated samples, the IF‐TTF concentration likewise decreased upon irradiation of the co‐dissolved photosensitizer, but these changes are linear as a function of the elapsed photolysis time. There is precedence for such observations, which imply kinetic competition between different mechanisms of solute degradation [45,46] . In this case, a O 2 (a 1 Δ g )‐mediated channel for IF‐TTF degradation appears to compete with an oxygen‐independent process that may involve a bimolecular reaction of the IF‐TTF with the sensitizer.…”

Design of AsLOV2 domain as a carrier of light‐induced dissociable FMN photosensitizer

“…In the case of AsLOV2 system, the spatial specificity of FMN action is determined by the applied light as only the incident light triggers the release of PS and a production of 1 O 2 . The efficiency as well as the mechanism of action of the GEPS system proposed in this work needs to be determined in an analogous study as the one very recently performed by Mogensen et al (2021).…”

Targeted photodynamic neutralization of SARS-CoV-2 mediated by singlet oxygen

“…SOPP3 is a very efficient protein photosensitizer for the production of singlet oxygen; however, the fluorophore encaged in SOPP3, FMN, shows significant photobleaching upon continuous and strong light stimulation. Recent studies have attributed this phenomenon to the transfer of electrons between FMN and surrounding amino acids within SOPP3, a process that can be partially reversed by compensating redox reactions [ 73 , 74 ]. Compared to the above two interesting and very detailed studies, the light intensity used in our studies was low and comparable to the light intensity used in the cuvette experiment of one study.…”