Michael Hymas, Sopida Wongwas, Simin Roshan, Abigail L. Whittock, Christophe Corre, Reza Omidyan and Vasilios G. Stavros

Mycosporine glycine (MyG) was produced by the fermentation of a purposely engineered bacterial strain and isolated from this sustainable source. The ultrafast spectroscopy of MyG was then investigated in its native, zwitterionic form (MyG_zwitter), via femtosecond transient electronic absorption spectroscopy. Complementary nonadiabatic (NAD) simulations suggest that, upon photoexcitation to the lowest excited singlet state (S₁), MyG_zwitter undergoes efficient nonradiative decay to repopulate the electronic ground state (S₀). We propose an initial ultrafast ring-twisting mechanism toward an S₁/S₀ conical intersection, followed by internal conversion to S₀ and subsequent vibrational cooling. This study illuminates the workings of the archetype mycosporine, providing photoprotection, in the UV–B range, to organisms such as corals, macroalgae, and cyanobacteria. This study also contributes to our growing understanding of the photoprotection mechanisms of life.

Journal of Physical Chemistry Letters. July 2024