Research
published in the Journal of Physical Chemistry Letters explained why
photodynamic cancer therapy causes night vision in patients. Photodynamic
therapy is a form of cancer treatment that uses light to destroy malignant
cells. The interesting side effect patients have reported is night vision seen
as silhouettes and outlines in the dark. Only now have researchers discovered
the mechanics of this phenomenon.
The Mechanics of Night Vision
Photodynamic
therapy involves injections of chlorin e6, a photosensitive compound. It’s the
reaction between chlorin e6 and rhodopsin in the retinal photoreceptors rods
that causes the apparent night vision to occur. Normally we see with visible
light because of a compound in our eye called retinal being triggered by
visible light. After triggering, retinal separates from rhodopsin, a
light-sensitive protein in the retinas of our eyes, and an electrical signal is
transmitted to our brain to interpret what we see. In the case of night vision
seen by these cancer patients, infrared light combined with the chlorin e6
changes retinal in the same way it does under visible light conditions. “This
explains the increase in night-time visual acuity,” chemist Antonio Monari,
from the University of Lorraine in France tells CNRS (French National Centre
for Scientific Research).
Using Molecular Simulation to Understand
Chemical Reactions
The
researchers used molecular simulation to model the movements of individual
atoms as well as the breaking or creating of chemical bonds. It took several
months of testing various simulations with millions of calculations before it
was able to accurately model the chemical reaction caused by infrared
radiation. “For our simulation we placed a virtual rhodopsin protein inserted
in its lipid membrane in contact with several chlorin e6 molecules and water,
or several tens of thousands of atoms,” Monari told CNRS.
Molecular
simulation is a powerful tool and can help us better understand fundamental
mechanisms. For example, it can help understand why certain DNA lesions are
better repaired than others and help select the best therapeutic molecules by
mimicking their interaction in a simulated model.
Reference: https://www.sciencealert.com/scientists-have-figured-out-how-a-cancer-treatment-gives-patients-night-vision
