Description
When light interacts with a biomolecule, it can initiate dynamical processes that unfold on ultrafast timescales. These processes, including energy relaxation, energy and charge transfer, and conformational changes, underlie many fundamental biochemical phenomena such as vision, photosynthesis, and the photoprotection of DNA against ultraviolet radiation. The remarkable speed of these elementary events is closely tied to their efficiency, making ultrafast optical spectroscopy an indispensable tool for probing their dynamics.
Such processes often proceed through conical intersections, special regions of a molecule’s potential energy landscape where electronic and nuclear motions become strongly coupled, driving the system into a distinctly quantum-mechanical regime. Conical intersections can be thought of as “molecular roundabouts,” where the photoexcited wavepacket determines which reaction pathway to follow.
In this talk, I will present examples of real-time visualization of conical intersections in biomolecules: the ultrafast isomerization of the retinal chromophore within the opsin protein, which initiates visual transduction, and the rapid energy dissipation in nucleobases that prevents photochemical reactions capable of damaging genetic material. I will also discuss the emerging potential of X-ray free-electron lasers for the direct observation of the quantum mechanical electronic coherences spawned at conical intersections.
