The chemical reaction that allows humans to see follows a hidden path that has been invisible to scientists for years.
April 29, 2026
Original Paper
A Machine-Learned Symbolic Committor for a Chemical Reaction: Retinal Isomerization
arXiv · 2604.24245
The Takeaway
Retinal isomerization is the process where a molecule in your eye changes shape when hit by light, sending a signal to your brain. Using AI to model this reaction, researchers found it follows a complex S-shaped path driven by dynamic motion. Standard chemistry models missed this because they only look at the energy landscape rather than the actual movement of the atoms. This discovery reveals that the foundation of human vision is far more sophisticated and kinetic than previously thought. Understanding this hidden pathway could help in the design of new light-sensitive materials and better treatments for vision loss.
From the abstract
The thermal cis-trans isomerization around the C$_{13}$=C$_{14}$ double bond of retinal is a prototypical high-barrier reaction whose mechanism hinges on subtle out-of-plane bending motions. We apply Artificial Intelligence for Molecular Mechanism Discovery (AIMMD) to N-retinylidene-lysine in vacuum, learning the committor from unbiased molecular dynamics trajectories generated by two-way shooting. Parametrizing the logit of the committor, rather than the committor itself, allows the neural netw