There are many ways of treating cancer, one of them is called photodynamic therapy (PDT). This method is based on application of photosensitive substances (experts call them photosensitizers) and light of a specific wavelength.
it’s No secret that many treatments have side-effects, but PDT has perhaps the most unusual: patients often start to see better in the dark. The reasons for this phenomenon experts did not know. Recently a group of researchers from France have discovered why patients there is a “night vision”.
Recall that one sees through a set of receptors in the retina: the cones and the sticks. The latter contain a huge amount of protein rhodopsin, which absorbs visible light due to the active compound called retinal.
Visible light causes retinal to change its chemical structure and separated from the protein. This process converts the light signal into electrical, then it can be interpreted by the visual cortex.
But as it turned out, this same mechanism can be run using different combinations of light and chemicals.
Earlier, experts have found that the introduction of chlorin E6 is the most important component of PDT, and under the influence of infrared radiation retinal changes as well as under the action of visible light.
“This explains the improve vision at night,” explains the chemist Antonio Monari (Antonio Monari) from the University of Lorraine in a press release from the National center for scientific research∎ France.
meanwhile, continues the scientist, we didn’t know how rhodopsin and its retinal active group interacts with chlorine. “This mechanism we managed to find out, through molecular modeling,” said Monari.
Explain what molecular modeling allows you to simulate biochemical reactions in a computer without the use of laboratory equipment.
Along with some complex chemical calculations, the researchers used molecular modeling tos to reproduce the movement of individual atoms as well as breaking or creating of chemical bonds.
Experiment with the computer models were processed over several months and required huge amount of computing. As a result, experts accurately reproduced the chemical reaction caused by infrared study. (In real life this process takes only a few nanoseconds.)
“to conduct our simulation, we have created a virtual protein rhodopsin embedded in its lipid membrane, and forced him to interact with several molecules of chlorin E6 and water, or several tens of thousands of atoms,” says Monari.
What happens when oncopatients receives a dose of photosensitizer? The chlorin E6 absorbs infrared radiation and reacts with oxygen in the eye tissues, transforming it into highly reactive singlet oxygen. This process actually leads to the destruction of tumor cells, but this is not its only effect.
As shown by molecular modeling, singlet oxygen can react with the retinal and strengthen “night vision”.
Now experts know the mechanism that underlies this unusual side effect, and thus can reduce the probability of its occurrence in patients who require PDT.
According to people who are faced with similar effect, they saw the silhouettes and outlines in the dark, which, of course, unpleasant.
Also, experts encourage people not to use chlorine E6, to be able to see in the dark.
the resulting data can be used to treat certain types of blindness or sensitivity to light.
the researchers Also once again point out the advantages of molecular modeling and modern powerful computers that help them to improve understanding of a phenomenon.
“Molecular modelling is already used to shed light on fundamental mechanisms, for example, to identify the reasons fornow, which some DNA damage recovered better than others. All this will allow you to select potential therapeutic molecules, simulating their interaction with the selected target,” concludes Monari.
Scientific article on the results of a study published in the Journal of Physical Chemistry Letters.