UvA PhD student: Evidence of chemical warfare found in plant proteins
Plants can provide evidence of a chemical weapons attack, UvA chemists discovered in collaboration with TNO and the Organization for the Prohibition of Chemical Weapons (OPCW). Together with other researchers, PhD student Mirjam de Bruin-Hoegée published on the subject in the chemical journal Analytical Methods.
Mirjam, why are chemical weapons banned?
“Chemical weapons such as mustard gas were widely used by the French and Germans in World War I. The use of chemical weapons was then forbidden; after 1925, the Geneva Protocol prohibited their use. Chemical weapons cause unnecessary suffering and target civilians and soldiers alike. In practice, civilians are the main victims because soldiers are usually protected by gas masks. Chemical weapons are also used to instil fear and create casualties. An ordinary bomb is thrown first, causing everyone to flee into a shelter. Then they use a chemical weapon that is generally heavier than air, making the shelter the most dangerous place. When people come out of the shelter, they become easy targets.”
Despite the ban, these weapons are still being used today.
“Indeed. In the war in Syria, the nerve agent sarin and chlorine gas are being used extensively. But there is also the poisoning of Russian double agent Skripal and the Russian opposition leader Navalny with Novichok. Even in the war in Ukraine, there are accusations flying back and forth that chemical weapons are being used, but that has yet to be investigated.
How often are chemical weapons used?
“It is difficult to say. In the last 10 years, there have been 70 reports of suspected use of chemical weapons. In 25 of those cases, it has been proven.”
How can you investigate whether chemical weapons were used?
“To do that, you must collect evidence such as pieces of concrete, weapon fragments, or blood from victims. Finding evidence is difficult because chemical weapons are very reactive, so you don't find much of the original toxin.”
How did you come up with the idea to test for them in plants?
“The measuring techniques are becoming increasingly sensitive, allowing you to detect lower concentrations of substances. We also know that the toxic substance in chemical weapons binds to proteins in the human body during poisoning. Since plants also have many proteins, we decided to investigate this in plants, too. Also, plants are everywhere, making them easily obtainable evidence.”
What happens in a plant when it is exposed to chemical weapons?
“The chemical weapon migrates into the plant and binds to proteins. We examined this for the nerve gases sarin, Novitjok, mustard gas, and chlorine. It turned out that toxins do indeed bind to the rubisco protein, commonly found in plants, something that has not been demonstrated before. We then remove the protein from the plant, cut it into small pieces, and measure the mass of the protein with mass spectrometry to see if the protein has become heavier. If the extra mass exactly matches the poison molecule, the plant has been exposed to a chemical weapon.”
Does it work in all plants?
“We have tested it in three species: bay leaf, basil, and nettles. But we expect it to be universally applicable because the rubisco protein that binds to chemical weapons is found in almost all plants.”
Is three months long enough to prove a chemical attack?
“We have tested for up to three months, so we expect that the evidence may be detectable in the plant for even longer. Often you can't travel directly to a site because of safety, but I estimate that three months is long enough.”
What has been the response to your research?
“The Organization for the Prohibition of Chemical Weapons also wants to include this in a standard procedure so that plants will be collected in an investigation of a poison gas attack. That's very gratifying.”
How will your research continue?
“We are now going to further investigate the use of chlorine gas, which is widely used in Syria. Because bleach also contains chlorine, it is difficult to distinguish between a chemical attack and when people who have cleaned their homes with bleach. That is often used as a defense in the case of a suspected chemical attack. We hope to find compounds characteristic to either the use of bleach or chlorine gas.”
