One of the strangest side effects of photodynamic therapy is that patients are better able to see in the dark.
Last year, researchers finally figured out why this happens: Rhodopsin interacts with a photosensitive compound called chlorin e6, a crucial component of this type of cancer treatment.
Scientists already knew that the organic compound is found in the eye, but it wasn't sensitive to the light.
Our brains see the electrical signal from the light that separates rhodopsin from retinal. While we don't get a lot of visible light at night, it turns out this mechanism can be triggered with light and chemistry.
Under visible light and with a chlorin injection, the eye changes in the same way.
Antonio Monari, a chemist from the University of Lorraine in France, told Laure Cailloce that the increase in night-time visual acuity was due to this.
We didn't know how rhodopsin interacted with chlorin. This mechanism is the one that we have succeeded in unraveling.
The team used a simulation to model the movements of individual atoms, as well as the breaking or creating of chemical bonds.
The simulation took several months to complete and was not able to model the chemical reaction caused by the radiation. In real life, the reaction would happen in a matter of seconds.
Monari said that they placed a virtual rhodopsin protein in contact with several chlorin e6 molecule and water, or tens of thousands of atoms.
As chlorin e6 absorbs the radiation, it interacts with the oxygen in the eye tissue, transforming it into highly reactive singlet oxygen, which can be used to boost night vision and destroy cancer cells.
The chemistry underpinning this weird side effect might be able to limit the chance of it happening in patients undergoing photodynamic therapy, who have reported seeing silhouettes and outlines in the dark.
It's not recommended to try to use chlorin e6 to give yourself night vision, but it could be harnessed to help treat certain types of blindness or over-sensitivity to light.
It's another example of how the most powerful computers on the planet can give us a deeper understanding of science than we would have otherwise.
Monari said that simulation is being used to shed light on fundamental mechanisms and enable the selection of potential therapeutic molecule by mimicking their interaction with a chosen target.
The research was published in a journal.
February 2020 is when the first version of this article was published.
