NOVO NORDISK FOUNDATION-SPONSORED VISITING SCHOLAR FELLOWSHIP RESEARCH PROJECT - 2024

Visiting Scholar: Andreas Erbs Hillers-Bendtsen (University of Copenhagen)

Stanford Faculty Advisor: Todd Martinez (Chemistry and Photon Science Directorate)
 

First Principles Simulation of Photoinduced Processes in Proteins

A crucial frontier in cellular biology is the elucidation of the composition and dynamics of subcellular structures with state-of-the-art “super-resolution microscopy” techniques being capable of reaching ~10 nm resolution using visible light. These techniques rely on the localization of individual fluorophores which can be stochastically switched between an OFF and ON state. Some of the most promising fluorophores used in such in vivo miscroscopy experiments are reversibly switchable fluorescent proteins (RSFPs) e.g. the now-ubiquitous green fluorescent protein, as they feature a wide palette of operating wavelengths, low phototoxicity, and regulatory sequence-based tagging making they ideal for biological imaging.

Despite much experimental work developing and utilizing RSFPs, many important aspects of their photophysical behavior remain unknown. In particular, the governing static variables and photochemical reactions leading to photoswitching behavior remain quite murky. The purpose of this project is to utilize recent breakthroughs in ab initio quantum chemistry and multi-electronic state dynamics to simulate the microscopic photochemical details of existing RSFPs and provide computational prediction of the operating characteristics of newly proposed RSFPs variants. This research will therefore establish insight into the complicated potential energy landscapes featuring at least the S₀ and S₁ electronic states, fluorescence or non-radiative decay, multiple protonation states, and excited state photochemistry or photoisomerization of RSFPs.

Combined with state-of-the-art time-resolved spectroscopy and biological imaging experiments performed using RSFPs at Stanford Bio-X, the project can potentially create a productive interdisciplinary feedback loop between experiment and theory. Together the combined theoretical and experimental approach can contribute to facilitate the design novel RSFPs for next generation biological imaging technology.