Dynamic Coupling of Chromophores and Proteins: Advancing the Study of Ultrafast Photochemical Reactions using QM/MM Simulations and Spectroscopy

• Applicants: Professor Dr. Karsten Heyne; Professor Dr. Igor Schapiro
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Biophysics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567099862

The project aims to understand the complex coupling betwen the chromophore and the protein upon light absorption, by combining multiscale simulations and experiments. To this end, we will develop and apply innovative computational methods, specifically Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory (MRSF-TDDFT), integrated in the quantum mechanics/molecular mechanics (QM/MM) method. This will enable more accurate simulations of ultrafast excited-state dynamics in complex biological systems. The focus will be placed on two specific protein families—phytochromes, which are important for light sensing in plants, and LOV domains, which play roles in blue light responses. The objective is to simulate their behavior when they absorb light, examining how excited states evolve over time and how these proteins interact with their chromophores. Additionally, the project will utilize advanced spectroscopic techniques to capture the rapid changes occurring in both proteins and chromophores during photochemical reactions. By employing polarization-resolved spectroscopy, we aim to map out the dynamics involved in energy transfer processes and structural changes at femtosecond to nanosecond timescales. A key goal is to investigate how specific protein residues influence the behavior of chromophores when they are excited by light. This includes studying interactions that occur during critical phases such as photoisomerization (the process where a molecule changes its structure upon light absorption) and other dynamic events. Finally, the findings from computational simulations will be compared against experimental results obtained from ultrafast spectroscopy experiments. The aim of this validation process is to ensure that the models developed accurately reflect the real behaviour observed in biological systems. Through these objectives, the project seeks to enhance our understanding of fundamental processes related to light absorption and energy conversion in biological systems, paving the way for future advancements in fields like biochemistry, photobiology, and materials science.

• DFG Programme: Research Grants
• International Connection: South Korea
• Partner Organisation: National Research Foundation of Korea, NRF
• Cooperation Partner: Professor Dr. Cheol Ho Choi